vulnerability and adaptation to climate change for bangladesh ||

VULNERABILITY AND ADAPTATION TO CLIMATE CHANGE FOR BANGLADESH

Vulnerability and Adaptation to Climate Change for Bangladesh

Edited by

S. Huq Bangladesh Centre for Advanced Studies,

Dhaka, Bangladesh

Z. Karim Bangladesh Agricultural Research Council,

Dhaka, Bangladesh

M. Asaduzzaman Bangladesh Institute of Development Studies,

Dhaka, Bangladesh

and

F. Mahtab Institute of Engineers, Dhaka, Bangladesh

SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

A C.I.P. Catalogue record for this book is available from the Library of Congress.

ISBN 978-90-481-5160-8 ISBN 978-94-015-9325-0 (eBook) DOI 10.1007/978-94-015-9325-0

Printed on acid-free paper

All Rights Reserved © 1999 Springer Science+Business Media Dordrecht

Originally published by Kluwer Academic Publishers in 1999 Softcover reprint ofthe hardcover lst edition 1999

No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical,

including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.

Contents

Tables

Figures

Preface

Overview Saleemul Huq and M Asaduzzaman

l. Introduction 2. The Physical Environment 2.1. Location 2.2. Physiograpy and Relief 2.3. Climate 2.4. Surface and Groundwater Hydrology 3. Social and Economic Settings 3 .I. Main Societal Features 3.2. Economy 4. Studies: Previous and Present 4.1. Previous Studies 4.2. The Present Study 4.3. Findings ofthe Present Study 5. Conclusion

Development of Climate Change Scenarios with General Circulation Models Ahsan Uddin Ahmed and Mozaharul A/am

I. 2. 2.1 2.2 2.3 3.

Introduction Estimation Methodology and Results Temperature Precipitation Evaporation Conclusions

Water Resources Vulnerability to Climate Change With Special Reference to Inundation Mozaharul A/am, Ain-Un Nishat and Saad M Siddiqui

I. 2. 3.

Introduction Methodology Description ofMIKEII Model

XI

X Ill

XV

2 2 2 4 4 5 5 7 7 7 8 8

10

14 16 16 18 18 19

22 23 25

3.1 3.2 4. 5.

6. 6.1 6.2 7. 7.1 7.2 7.3 8.

General Model Regional Model Assumptions for Model Runs Creation of Water Depth Spatial Database for the Year 1990, 2030 and 2075 Assumptions for Assessment of the Changes of Land Type MPO Land Types Land Type Change Matrix Assessment of the Changes ofLand Type Existing (1990) Land Type and Area Land Type and Area in 2030 Land Type and Area in 2075 Conclusions

Climate Change Vulnerability of Crop Agriculture Zahurul Karim, Sk Ghulam Hussain and Ahsan Uddin Ahmed

1. 2. 3. 3.1 3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.6 3.2 3.3 4. 5. 6.

Introduction General Vulnerability of Crop Agriculture in Bangladesh Climate Change Induced Vulnerability to Crop Production Effect on Aggregated Production ofFoodgrain Climate Models Crop Models HYV AusRice HYV Aman Rice HYV Boro Rice Wheat Effect of Climate Change on Crop Growing Season Moisture Stress Scenario Implication of Climate Change Management Options for Adaptation to Reduce Vulnerability Conclusions

Assessment of Foodgrain Production Loss Due to Climate Induced Enhanced Soil Salinity Mohammad Habibullah, Ahsan Uddin Ahmed and Zahurul Karim

1. 1.1 2. 3. 3.1 3.2 4.

Introduction The Soil Salinisation Process: An Overview Approach and Methodology Results Soil Salinity Development Possible Impact of Soil Salinity on Foodgrain Production Conclusions

vi

26 26 26

27 27 28 29 30 31 33 33 38

40 40 43 43 43 45 45 46 46 46 47 47 48 51 51

56 56 57 58 58 62 69

Beach Erosion in the Eastern Coastline of Bangladesh S.M Rakibu/ Islam, Sa/eemu/ Huq and Anwar Ali

I. 2. 2.1 2.2 2.3 3. 4. 4.1 4.2 4.3 4.4 5. 6. 6.1 6.1.1 6.1.2 6.1.3 6.2 6.3 7. 7.1 8. 9.

Introduction Coastal Morphology of Bangladesh Eastern Region Central Region Western Region Review of Erosion Studies in Bangladesh Erosion Dynamics or Causes of Erosion Discharge Current Tide Monsoon Current Storm Surges Theory of Erosion due to Sea Level Rise Survey and Study Area First Part Bakkhali River Valley Southern Beach Plain Nhila-TeknafPlain Second Part Third Part Data Collection Methodology of Taking Readings Data Analysis, Results and Discussions Recommendations

Vulnerability of Forest Ecosystems of Bangladesh to Climate Change Ahsan Uddin Ahmed, Neaz Ahmed Siddiqi and Rawshan Ali Choudhuri

I. 2. 2.1 2.1.1 2.1.2 2.1.3 2.1.4 2.2 2.3 2.4 2.5 2.6 2.7 2.8 3.

Introduction The State of Forests in Bangladesh Natural Hill Forest Ecosystem Dipterocarp Forest Savanna Bamboo Freshwater Swamp Forests Natural Sal Forest Ecosystem Littoral Mangrove Ecosystem Plantation Forest Ecosystems Village Forest Ecosystem Forest Fauna Forest Product Requirement and Productivity Deforestation and Forest Degradation General Impacts of Climate Change on Tropical Forests

vii

72 72 75 75 75 75 78 78 78 79 79 79 82 82 82 82 84 84 84 84 84 85 90

94 94 95 95 95 95 97 97 97 98 98 99 99

100 101

4. 5. 5.1 5.1.1 5.1.2 5.1.3 5.2 5.3 6.

Impacts on Forests in Bangladesh Impacts on Mangrove Forests General Features of the Sundarbans 0 ligohaline (or miohaline) Zone Mesohaline Zone Polyhaline Zone Possible Impacts on the Sundarbans Ecosystem Probable Adaptation Alternatives Conclusions

Fish Resources Vulnerability and Adaptation to Climate Change in Bangladesh M Youssouf Ali

1. 2. 2.1 2.2 2.3 3. 3.1 3.1.1 3.1.2 3.2 3.3 3.4 4.

4.1 4.2 4.3 4.4 5.

Introduction Primary Fish Habitat Rivers and their Floodplains Beels Estuaries Fish Species Diversity Inland Waters Large Sized Fishes Small Sized Fishes Marine Water of the Upper Bay Prawns Exotic Species ofFishes Description of Main Fisheries Likely to be Affected by Climate Change Marine and Estuarine Capture Fisheries Fresh Water Capture Fisheries Freshwater Pond Culture of Fisher Brackish Water Shrimp Farming in the Coastal Districts Probable Adaptation Alternatives

Adaptation to Climate Change in Bangladesh: Future Outlook Ahsan Uddin Ahmed, Mozaharul A/am and A. Atiq Rahman

1. 2. 3. 3.1. 3.2. 3.2.1. 3.2.2.

Introduction Vulnerability to Climate Change Response to Climate Change Types of Adaptation Anticipatory Adaptation Measures Bear Losses Share Losses

viii

102 103 104 105 105 105 106 108 108

114 114 115 115 116 117 118 118 118 119 119 120

120 121 121 121 122 123

125 127 129 130 130 130 130

3.2.3. 3.2.4. 3.2.5. 3.2.6. 3.3. 3.3.1. 3.3.2. 3.3.3. 3.3.4. 3.4. 3.5. 4.

Modify the Threat Prevent Effects Change Use Change Location Possible Actors and their Respective Domains Global Level National Level Sub-national Level Local Level Opportunities for Bangladesh: An Assessment Challenges of Managing Adaptation Way Ahead

Subject Index

ix

130 131 131 131 132 132 133 134 134 134 137 138

145

Tables

Overview Table I. Major sectoral share of GDP 7

Development of Climate Change Scenarios With General Circulation Models Table 1. Extent of changes in temperature, precipitation and evaporation I7

Water Resources Vulnerability to Climate Change With Special Reference to Inundation Table I. The fluctuations of values of the parameters considered with

respect to their values under base year situation. 23 Table 2. Classification of water levels 28 Table 3. MPO land types 29 Table 3.I. Land type change matrix for FOland (0-30 em) 29 Table 3.2. Land type change matrix for FI land (30-90 em) 30 Table 3.3. Land type change matrix for F2land (90-I80 em) 30 Table 3.4. Land type change matrix for F3 land (180-360 em) 30 Table 3.5. Land type change matrix for F4land (>360 em) 3I Table 4. The existing ( I990) land area by land types (in sq. km) 3I Table 5. Changes of land from one class to the others in 2030 (in sq. km) 33 Table 6. Changes of land from one class to the others in 2075 (in sq. km) 36

Climate Change Vulnerability of Crop Agriculture Table 1. Crop statistics of major cereals for the fiscal year 1994-95 41 Table 2. Rice and wheat production under different climate change

scenarios 46 Table 3. Percent change in Boro yields under different climate scenarios

and irrigation levels 48

Assessment of Foodgrain Production Loss Due to Climate Induced Enhanced Soil Salinity Table I. Soil salinity classification on the basis of electrical conductivity 57 Table 2. Soil salinity distribution under baseline condition (CCSO) 62 Table 3. Soil salinity distribution under the moderate climate change

scenario (CCS1) 62 Table 4. Soil salinity distribution under the severe climate change

scenario (CCS2) 65 Table 5. Loss of Aus production under the three scenarios (without

adaptation) 65 Table 6. Loss of Aman production under the three scenarios (without

adaptation) 66 Table 7. Total loss in foodgrain production under the three climate

xi

Table 8. Table 9. Table 10.

change scenarios Loss of Aus production under adaptation scenarios Loss of Aman production under adaptation scenarios Overall foodgrain production loss due to soil salinity with adaptation

Beach Erosion in the Eastern Coastline of Bangladesh

66 67 68

68

Table 1. Land area in the Meghna-estuary (in sq. km) 76 Table 2. Change detection study for the period 1960-84 (in sq. km) 76 Table 3. Areas of mainland and char/islands and number of chars/islands

in 1973 and 1987 (in sq. km) 77 Table 4. Comparative statement of erosion and accretion 77 Table 5. Erosion due to SLR for two different erosion rates (area in sq.

~ ~ Table 6. Coastal recession due to SLR based on field survey, August 1995 85 Table 7. Recession distance per 1 em rise is sea level for three cases of30

em, 75 em and 100 em SLR 87 Table 8. Loss of land due to SLR 87

Vulnerability of Forest Ecosystems of Bangladesh to Climate Change Table 1. Land area classification ofBangladesh 95 Table 2. Classified and unclassified state forest land by physical cover (in

hectares) 97 Table 3. The general vegetation types in respect to soil salinity zones 106

Fish Resources Vulnerability and Adaptation to Climate Change in Bangladesh Table 1. Areas under different types of inland open waters areas 117 Table 2. Brackish water shrimp farm areas in the coastal districts of

Bangladesh and total production of shrimp from the farms 122 Table 3. Quantity of shrimp exported and income earned in different year 122

Adaptation to Climate Change in Bangladesh: Future Outlook Table 1. Possibilities of awareness induced adaptations with respect to

socio-economic activities 13 5 Table 2. Some identified adaptation options with respect to water and

agriculture sectors 136

xii

Figures

Overview Figure I. Geographical location of the country 3 Figure 2. Surface water system of the region 6

Development of Climate Change Scenarios With General Circulation Models Figure 1. Comparative analysis of GCM model outputs with observed data 15 Figure 2. Changes in mean monthly temperature 17 Figure 3. Changes of average precipitation 18

Water Resources Vulnerability to Climate Change With Special Reference to Inundation Figure I. Schematic representation of river network with MIKE II

boundary station and considered embankment 24 Figure 2. Relationship between changes of runoff and rainfall for north-

west region of Bangladesh. 25 Figure 3. Logarithmic trend ofland types 29 Figure 4. Spatial distribution of existing land types 32 Figure 5. Spatial distribution ofland types in 2030 34 Figure 6.I. Changes ofFO land in different projection years 35 Figure 6.2. Changes ofFiland in different projection years 35 Figure 6.3. Changes of F2 land in different projection years 35 Figure 6.4. Changes ofF3F4land in different projection years 36 Figure 7. Spatial distribution ofland types in 2075 37

Climate Change Vulnerability of Crop Agriculture Figure I. Administrative map of Bangladesh. Study regions selected are

marked with a dot 44 Figure 2. Status of organic mater content in the soils of Bangladesh 50

Assessment of Foodgrain Production Loss Due to Climate Induced Enhanced Soil Salinity Figure I a. Area affected by soil salinity in the month of August 59 Figure I b. Area affected by soil salinity in the month of October 60 Figure I c. Area affected by soil salinity in the month of December 60 Figure I d. Area affected by soil salinity in the month of February 6I Figure I e. Area affected by soil salinity in the month of April 61 Figure 2. Soil salinity distribution for December under the three climate

change scenarios 63 Figure 3. Soil salinity distribution for April under the three climate change

scenarios 64 Figure 4. Total loss in foodgrain production under climate change

Xlll

scenarios 66 Figure 5. Production loss under adaptation scenario 68

Beach Erosion in the Eastern Coastline of Bangladesh Figure I. Map of Bangladesh showing three regions of coastal area 7 4 Figure 2. Erosion phenomenon due to sea level rise 80 Figure 3. Map of Bangladesh showing study area 83 Figure 4. Map showing cross sectional points 86 Figure 5. Map showing section considered for calculation 88 Figure 6. Map showing land recession due to sea level rise 89

Vulnerability of Forest Ecosystems of Bangladesh to Climate Change Figure I. Forest areas of Bangladesh 96 Figure 2. The Sundarbans forest 100 Figure 3. Location of Mangrove forests in Bangladesh 103 Figure 4. Salinity Zones in the Sundarbans forest 105 Figure 5. Forest succession in the three salinity zones in respect to land

elevation and tidal height I 09

Adaptation to Climate Change in Bangladesh: Future Outlook Figure 1a. Pathway of impacts of water in monsoon 128 Figure lb. Pathway of impacts of water in winter 129 Figure 2. Different levels of interactive management of adaptation 133 Figure 3. The adaptation cycle through space and time 137 Figure 4. Framework for managing adaptation options 138

xiv

PREFACE

Bangladesh faces many challenges. So long it has been mainly the traditional ones of socioeconomic development and eradication of poverty. Environment as a major factor in this process has only recently entered the scene. But even before environmental considerations in the development process has become the normal practice, the spectre of climate change has reared its ugly head. While Bangladesh is not unique among developing countries in being at the receiving end regarding the causes and consequences of climate change, both in the literal and allegorical sense of the term, the fact remains that it has made the prospects for sustainable socio-economic development in the country much more complex and formidable than before. Both for her own sake and the sake of the global community at large, therefore, Bangladesh has to initiate actions at various levels to face the challenge from now on. The present study is a part of that process.

In 1996, the Governments of USA and Bangladesh together decided to initiate a comprehensive study on climate change in Bangladesh. A unique consortium of public and non-governmental research organisations with support from the relevant administrative arms of the Government carried out the study over 1996 and 1997. The report has been accepted by the Government and several of its recommendations are in the process of implementation.

While the direction of climate change is broadly certain, its details leave much scope for speculation and interpretation. Only over time and with continuous studies will these be more definitively known with clearer ideas about desirable direction and level of policy intervention. It is therefore essential that the study results be put in the public domain. The publication of this volume, we hope, will fulfil that condition.

A complex and comprehensive exercise such as the present one is never possible without the help and encouragement from various people and organisations. Among them, we thank the US Country Studies Management Team who provided funds for the study, the various arms of the Government of Bangladesh, particularly the Directorate of Environment and their Directors General at different times during the life of the project, the National Steering Committee and its various members some of whose enthusiasm has been rather infectious and participants at various workshops whose comments helped improve the content and presentation in the various reports of the study. We would like to particularly express our sense of gratitude to Mr. M. Reazuddin, at present Deputy Director in the Directorate of Environment for his never-failing help in passing through the labyrinth of rules and regulations during the course of the study. We thank the various consultants and experts who have contributed to the various sub-components of the study. Finally, we are grateful to Kluwer Academic Publishers without whose perseverance the study would probably never have seen the light of the day.

Editors

OVERVIEW

SALEEMUL HUQ Executive Director Bangladesh Centre for Advanced Studies (BCAS)

M. ASADUZZAMAN Research Director Bangladesh Institute of Development Studies (BIDS)

1. Introduction

Bangladesh, it is by now well known, is one of those poor countries which face the irony of adapting to and mitigating the consequences of global warming and climate change which are, by and large, not of their own making while they have in general the least human, societal, technological and fmancial capability for such adaptation and mitigation. Yet, they, including Bangladesh have signed international agreements and treaties related to climate change and abide by their provisions. Towards this end, they need to equip themselves with the knowledge of potential climatic changes and their national consequences, particularly vulnerabilities and fmd ways and means to adapt to and mitigate them. While the generation of such a knowledge base is only the first step towards actions at local, national and international levels, this is an absolutely necessary activity. What is more, this has to be an ongoing exercise as the nature of investigation leaves many scopes for uncertainties, ambiguities and differences in interpretation. In Bangladesh, as the discussion that follows would amply show such a process has been continuing for at least one decade and the present study is only one, albeit an important one, link in this chain.

An examination and analysis of the climate change induced vulnerabilities has to be understood against the backdrop of the physical, economical and societal environment of the country. They not only provide the benchmark against which the vulnerabilities are to be assessed but also the potentials for adaptation to them. This overview while it summarises the study fmdings attempts to provide a concise but clear understanding of such factors. To these we now turn.

2 S. HUQ and M. ASADUZZAMAN

2. The Physical Environment

The physical environment of Bangladesh is both diverse and complex, and both traditional and modem systems of land use are very closely adapted to the heterogeneous conditions. This heterogeneity has important implications for climate change vulnerability. Moreover, the physical environment and technology are not static. Thus the changes are taking place in the hydrological system which influence land use. Rapid and frequent changes are taking place in the river system, part of it is due to human intervention. A brief description on physical settings is presented here.

2.1. LOCATION

Bangladesh is a South Asian developing country located between 20°341 to 26°381 North latitude and 88°011 to 92°421 East longitude with an area of 147,570 sq. km and a population of 122.1 million (BBS, 1997a). Geologically it is a part of the Bengal Basin filled by sediments washed down from the highlands on three sides of it, and especially from the Himalayas, where the slopes are steeper and the rocks less consolidated. It is bordered on the west, north and east by India, on the south-east by Myanmar and on the south by the Bay of Bengal. Figure-1 shows the geographical location of Bangladesh.

2.2. PHYSIOGRAPHY AND RELIEF

Except for the hilly regions in the north-east and south-east part, the whole country consists of low and flat land formed mainly by the Ganges and the Brahmaputra River systems. A network of rivers with their tributaries and distributaries criss-crosses the country. While physiographically the country can be divided into hills, uplifted land blocks and alluvial plains (Rashid, 1991), most of it would fall in the latter category with very low mean elevation above the sea level.

Floodplains of the major rivers, occupy 80 per cent of the country, are generally smooth relief comprising broad and narrow ridges (former river levees) and depressions. Differences in the elevation between adjoining ridge tops and depression centres range from less than 1 meter on tidal floodplains to 1 meter to 3 meters on the main river and estuarine floodplains, and upto 5 meters to 6 meters in the Sylhet Basin in the northeast. Only in the extreme north-west land elevations exceed 30 meters above the mean sea level (MSL).

The uplifted land blocks are mainly Madhupur and Barind tracts were formed of unconsolidated clay, possibly of the Pleistocene age and generally stand 1 meter to 5 meters above the adjoining floodplains, although in some places they reach up to 25 meters higher than the adjoining floodplain.

Hills along the northern and eastern borders of the country are formed mainly of unconsolidated tertiary sands and shales. These have been uplifted, folded, faulted and dissected to form linear ranges variously reaching 10 meter to 1 000 meter above MSL. Slope generally is very steep, but there are some areas with moderate or gentle slopes.

OVERVIEW

FIGURE 1. Geographical location of the country

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2.3. CLIMATE

The climate of Bangladesh is influenced primarily by summer and winter winds and partly by pre-monsoon and post-monsoon circulation. The south-west monsoon originates over the Indian Ocean and carries warm, moist, and unstable air. The easterly trade winds are also warm, but relatively drier.

The country has a humid, warm, tropical climate which is fairly uniform throughout the country. There are three main seasons: (i) a hot summer with the highest temperature (5 to 10 days with maximum more than 40°C in the west), highest rate of evaporation and erratic but occasional heavy rainfall from March to June, (ii) a hot and humid monsoon with heavy rainfall from June to October with about two-thirds of the mean annual rainfall occurring during this time, and (iii) a relatively cooler and drier winter from November to March. Maximum temperatures range between 20-40°C and minimum temperatures can fall below SOC in the north though frost is extremely rare.

The mean annual rainfall varies widely by geographical location within the country, ranging from 1,200 mm in the extreme west to 5,800 mm in the east and north-east. There are three main periods of rainfall with distinct sources of precipitation: (i) the western depression of winter, (ii) the pre-monsoon early thunderstorms known as the Nor'westers (North-westerlies) during April-May, and (iii) the summer rains from the south-west trades known as the monsoons. The main rainy period begins with the onset of the moisture-laden south-west trades which are drawn to the Indian sub-continent by the intense heat and consequent low pressure over Punjab (in Pakistan and India) and the Upper Ganges Valley and the filling up of the equatorial lows by air masses from these hot areas. While the connection of these wind movements and rainfall have been studied rather in-depth, its possible connections with El Nino have only now begun to attract attention as a major possible influence on climatic pattern in the Sub-continent.

2.4. SURF ACE AND GROUNDWATER HYDROLOGY

Bangladesh's surface water and groundwater resources play vital roles in agricultural, forestry, fisheries and livestock production. They also play significant roles in settlement patterns, domestic water supply and communications and indirectly in sanitation and health. Differences in depth and duration of seasonal flooding on different soil and land types strongly influence the kinds of crops grown and cropping rotations.

The surface water system of the country is dominated mainly by the three major river systems, the Ganges-Padma, the Brahrnaputra-Jamuna and the Meghna river systems. These river systems cover about 7 per cent of the surface of the country and discharge about 142 thousand cubic meters per second in to the Bay of Bengal at peak periods

OVERVIEW 5

(Rahman et al., 1990). It is estimated that in an average year 1.181 million cubic meters water flows out to the sea of which 1.07 million cubic meters or 91 per cent come from India (Rashid, 1991).

This vast outflow is second only to that of the Amazon system both in breadth and total annual volume. The Padma-Lower Maghna is the third largest river system in the world. The annual picture conceals important fluctuations in seasonal inflow during the year. About 60 per cent of inflow occurs during the months of July, August and September and the volume of water in August is nearly seven times as much as that in February. Since nine-tenths of the flow is received from outside of the country, the rise and fall of the water level in rivers is governed principally by the amount of rainfall beyond its political boundaries. Figure-2 presents the surface water system of the region.

Groundwater is an important resources of Bangladesh and extensively used for both domestic and agricultural needs. There is a fairly extensive aquifer at a very shallow depth of 20-40 feet below ground level. A deeper aquifer at about 200-400 feet depth has also been identified in many parts of the country which has been used for irrigation purposes.

3. Social and Economic Settings

The socio-economic environment of Bangladesh is characterised by high population density, widespread poverty, predominance of rural populations and low rates of economic growth. The majority of rural households depend on agriculture, fisheries and other forms of primary activities. A brief reflection on socio-economic settings of the country as given below will help to understand the social vulnerability of the country.

3 .1. MAIN SOCIETAL FEATURES

Bangladesh has a very large population with a population density of about 755 persons per sq. km and an annual growth rate of 1.6 per cent per annum in the recent years (World Bank, 1997). The total number of households in the country is 22.3 million out of which 20 million are rural and remaining 2.3 million are municipal households. The literacy rate of the population is estimated at 32.4 per cent for people above 7 years of age. The life expectancy at birth (1996) is estimated as 59 years for both sexes (BBS, 1997a). Between 40 to 45 million people in Bangladesh, out of a rural population of 89 millions, are poor. Of these, around 20 million, that is 22% of total rural population, are suffering from extreme poverty (Rahman, 1994).

1 excluded the loss of evaporation, evapotranspiration and deep percolation


FIGURE 2. Surface water system of the region

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OVERVIEW 7

3.2. ECONOMY

Agriculture, manufacturing industry and various services (such as transport, trade, services and housing) are the major economic sectors of the country. While there are some debates regarding the direct relative contribution of agriculture to national income, two facts remain undisputed which are a falling trend in its share and secondly, its paramount importance despite the fall because of the dependence of most other sectors or activities (with the significant exception of ready-made garments manufacturing) either for processing the products of or servicing the sector.2 Sectoral shares in GDP for the year 1989-90 and 1994-95 at constant (1989-90) prices and current prices are presented in Table-1.

TABLE 1. Major sectoral share ofGDP (%)

Sector GDP at current Prices GDP at constant prices 1989-90 1994-95 1989-90 1994-95

Agriculture 25.62 20.32 25.62 21.31 Transport 10.78 12.66 10.78 11.39 Manufacturing 11.44 12.88 ~ 1.44 13.62 Trade 16.27 16.80 16.27 17.42 Construction 8.98 8.95 8.98 9.00

Source: BBS. 1997b

The economic development of the country depends upon a host of factors one of which is high and stable level of agricultural production. Agricultural growth, however, critically depends upon weather conditions, a variable which is subject to variability due to the climate change (see later). Manufacturing and service sector outputs which are dependent to a large extent upon processing of agricultural output or servicing agriculture become consequently variable.

4. Studies: Previous and Present

4.1. PREVIOUS STUDIES

A number of studies have been conducted over the years to assess the extent of vulnerability of Bangladesh to climate change and quantify the possible impacts wherever possible (Mahtab, 1989; BCASIRA/Approtech, 1994; ADB, 1994; BUP/CEARS/CRU, 1994). The results of all these studies and their outputs have successfully raised awareness about climate change issues, particularly their impacts both in Bangladesh as well as internationally. One of the important results was the creation of an inter-ministerial steering committee on climate change by the Government of Bangladesh (GOB) with the

2 Very recently the Bangladesh Bureau of Statistics revised the national GDP at current market prices and at constant market prices of 1989-90. For the year 1994-95, the agricultural contribution to the GDP at constant market prices was about 21.3%. It was about 25.6% in 1991-92.


Minister of Environment and Forests as its chairperson to deal with all issues relating to climate change.

In 1996, the Government of Bangladesh and the Government of the United States of America through its Country Studies Management Team (USCMT) decided to support and continue further work in this area. This book represents mainly the outcome of the various studies, particularly those related to vulnerabilities undertaken under this programme over the period 1996 and 1997 with some additional material on adaptation which had not been dealt with in much detail in the main study.

4.2. THE PRESENT STUDY

The Country Study on Climate Change consisted of four integral elements: (i) Greenhouse Gas (GHG) Emission Inventory ( ii) Vulnerability and Adaptation Assessment (iii) Mitigation Assessment (iv) Dissemination and Awareness Raising

While the present book reports mainly on the second theme, particularly vulnerabilities, readers may wish to study the reports of the other components for a better understanding of the general inter -linkages among these various issues in managing climate change and more particularly as a guide to national action in a poor country such as Bangladesh.

The vulnerability and adaptation component of the study was divided into seven subcomponents of which only four received major attention due to time, resource and severe data constraints. The major sub-components were (i) Scenario Development; (ii) Agriculture; (iii) Coastal Zone and (iv) Water Resources. Foreshy, fisheries and livestock received some minor and at best qualitative treatment While data availability dictated the choice of the components, it would be only appropriate, however, to discuss briefly the other logic behind their choice.

The reason for the choice of the first component was obvious. Unless one knows, however crudely, the possible changes in the climate over the baseline situation, there is no way to analyse their physical impacts and assess consequent vulnerabilities. One of the immediate impacts of climate change will be reflected in the water availability and its seasonal and spatial spread. This, in tum, will affect major economic sectors such as agriculture directly. On the other hand, the coastal zone would be particularly vulnerable to climate change and sea level rise. Indeed, water availability, its quality and consequent physical and agricultural changes will all converge in the coastal zone to encapsulate the essence of future trials and tribulations of Bangladesh in a world with changing climate.

4.3. FINDINGS OF THE PRESENT STUDY

Two climate change scenarios were considered for the study, one with a moderate climate change likely to take place by the year 2030 and the other being a severe

OVERVIEW 9

climate change likely to occur by the year 2075. A General Circulation Modelling (GCM) exercise indicated that the average increase in temperature would be 1.3°C and 2.6°C for the two projection years, 2030 and 2075, respectively. It was also revealed that the rise in winter temperature would be more compared to that during the monsoon probably due to significant increase in monsoon precipitation which could also cause severe flooding in the future. Moreover, there would be no appreciable precipitation in the winter resulting in very high evaporation rates which may cause severe drought conditions in the country making irrigation absolutely vital but more costly for continued agricultural growth.

An extensive water sector modelling was performed which was coupled with a GIS analysis to study the level of inundation under different climate change scenarios. It was found that 8% and 17% of existing upland areas along with 56% and 62% of existing slightly flooded areas would become extremely vulnerable to flood. It was assumed that the country would construct the proposed F AP (Flood Action Plan) embankments by the year 2075. But such structures could not keep the flood water away from the agricultural lands and settlement areas. It was also shown that the lower Ganges floodplain would become more vulnerable compared to the rest of the country. If the proposed F AP projects are implemented, the north-central region of the country, however, would become flood-free.

A simulation study was conducted to assess the vulnerability of foodgrain production due to climate change. Several GCM scenarios were tested by using CERES-rice and CERES-wheat models. Both for rice and wheat, it has been noted that yields decrease over the baseline levels in all seasons and locations, while Aus would be the most vulnerable crop under a changed climate.3 It was revealed that a rise in temperature associated with increased water stress would lower Boro rice and wheat production significantly. Moreover, a doubling of C02, despite its positive effects, would not be

able to offset the production shortfall if the temperature rises by 4°C.

An attempt was made to analyse the rice production loss due to climate induced changes in salinity. It was found that the entire coastal area comprising of about one third of the country would no longer be suitable for Boro and wheat cultivation. Under severe climate change scenario more areas would be affected by relatively higher salinities restricting foodgrain production. It was also revealed that even if there were adaptation measures the overall shortfall in rice production due to increased soil salinity under severe climate change scenario would be more than what was being observed at present.

An accelerated sea level rise would pose a threat to the flat sandy beaches along the south-eastern coast line of Bangladesh. Bathymetric information combined with survey

3 There are three rice crops a year. Aman is grown during partly monsoon and partly dry season, bora is mainly irrigated and grown during the practically rainless months while aus is cultivated during the wet

months. A us is most vulnerable to weather conditions.


data were fed into Brunn's equation and it was found that about 5.8 sq. km area along the beach would be eroded by 2030, while twice as much would be eroded by the year 2075. Physical observations suggested that some of the prime agricultural lands and recreational beach areas would be lost in the process. Only a selected small part of the beach was studied for this purpose. Other areas along the beach are known to be far more vulnerable to beach erosion, In those areas, the extent of damage would, of course, be far greater.

5. Conclusion

The study on vulnerability and adaptation to climate change presented in this publication has already been accepted by the Government of Bangladesh and has led to several policy actions including a publicity campaign through the print and electronic media to make people better aware about the problems and possible local actions. But more importantly the study has shown that there are major uncertainties in understanding the extent and gravity of possible adverse effects in the future. These are at best crude estimates of some of the direct physical changes. What the indirect economic and social changes would be or how extensive they would be could only be guessed at the moment. One thing is certain, it is going to be very .painful for a very large group of people who are poor and who may go hungry and be under constant threat of inundation in areas, particularly in the coastal zone. One needs, therefore, better information, better tools of analysis and more comprehensive and better focused exercises than those that have been reported here for addressing the problem. This has become also more urgent as Bangladesh is now treaty bound to submit its National Communication (NC) to the UN on a regular basis on aspects such as inventories of GHG sources and sinks and national programme to mitigate and adapt to climate change.

References

ADB, 1994. Climate Change in Asia: Bangladesh Country Report. Asian Development Bank, The Philippine.

BBS, 1997a. Statistical Pocket of Bangladesh. Bangladesh Bureau of Statistics, Government of Bangladesh.

BBS, 1997b. National Accounts Statistics of Bangladesh (Revised Estimates, 1989-90 to 1994-95). Bangladesh Bureau of Statistics, Government of Bangladesh.

BCAS/RA/ Approtech, 1994. Vulnerability of Bangladesh to Climate Change and Sea Level Rise.· Concepts and Tools for Calculating Risk in Integrated Coastal Zone Management, Technical Reports Volumes I and !!, Summary Report and Institutional Report. Bangladesh Centre for Advanced Studies (BCAS), Dhaka, Bangladesh; Reseorce Analysis, The Netherlands; Approtech Ltd, Dhaka, Bangladesh.

OVERVIEW 11

BUP/CEARS/CRU, 1994. Bangladesh: Greenhouse Effect and Climate Change, Briefing Document, No. 1 - 7. Bangladesh Unnayan Parishad, Dhaka, Bangladesh; Centre for Environmental and Resource Studies, University of Waikato, Hamilton, New Zealand and Climate Research Institute, University of East Anglia, Norwich, United Kingdom.

Mahtab, F., 1989. Effect of Climate Change and Sea Level Rise on Bangladesh,for Expert Group on Climate Change and Sea Level Rise. Commonwealth Secretariat, London, 1989.

Rahman, A.A., Huq, S., and Conway, G.R., 1990. Environmental Aspects of Surface Water Systems of Bangladesh: An Introduction, In Environmental Aspects of Surface Water Systems of Bangladesh, A. A. Rahman, S. Huq and G. R. Conway (Eds.), University Press Ltd. Dhaka, Bangladesh.

Rahman, H. Z., 1994. Rural Poverty Up-date, 1992-93. Bangladesh Institute of Development Studies (BIDS), Dhaka, Bangladesh.

Rashid, H.E., 1991. Geography of Bangladesh (Second Revised Edition). The University Press Ltd., Dhaka, Bangladesh.

World Bank, 1997. World Development report, 1997. The State in a Changing World, Oxford University Press, Inc., 200 Madison Avenue, New York, N.Y.l0016, USA.

DEVELOPMENT OF CLIMATE CHANGE SCENARIOS WITH GENERAL CIRCULATION MODELS

AHSAN UDDIN AHMED Senior Specialist

Bangladesh Unnayan Parishad (BUP)

MOZAHARUL ALAM Research Fellow

Bangladesh Centre for Advanced Studies (BCAS)

ABSTRACT

The vulnerability to climate change for different sectors was assessed based on climate scenarios for two projection years 2030 and 2075. These climate scenarios were developed by using General Circulation Model. Models were run to find correlation with the observed time-series data for I 0 particular points distributed all over the country both for base and projection years. The model estimated monthly average rate of change in temperature and precipitation for those locations were superimposed on the observed time-series monthly average data to obtain data for the projection years.

The results revealed that the average increase in temperature would be I.3°C and 2.6°C for the years 2030 and 2070, respectively. It was found that there would be a seasonal variation in changed temperature: I.4°C change in the winter and 0. 7C in the monsoon months in 2030. For 2070 the variation would be 2. rc and I. 7C for winter and monsoon, respectively. For precipitation it was found that the winter precipitation would decrease at a negligible rate in 2030, while in 2075 there would not be any appreciable rainfall in winter. On the other hand, monsoon precipitation would increase at a rate of I2 per cent and 27 per cent for the two projection years, respectively.

It was found that there would be excessive rainfall in the monsoon causing flooding and very little to no rainfall in the winter forcing drought. It was also found that there would be drastic changes in evaporation in both winter and monsoon seasons in the projection year 2075. It was inferred from the GCM output that moderate changes regarding climate parameters would take place for the projection year 2030, while for the projection year 2075 severe changes would occur.

14 A.U. AHMED and M. ALAM

1. Introduction

A 'climate change scenario' is defmed as a physically plausible set of changes in meteorological variables, consistent with generally accepted projections of global temperature change (Strezepek and Smith, 1995). Climate change scenarios are often developed with the help of General Circulation Models (GCM). These models are best suited for predicting irrformation regarding the climate parameters for any particular geographic position at any future point of time considering either 1XC02 or 2XC02

concentration with respect to C02 concentration of a reference year. The information base concerning the regional and seasonal details of the climate response to greenhouse gas forcing was based on equilibrium (steady-state) response experiments; undertaken mostly by the following institutions: Goddard Institute for Space Studies; National Centre for Atmospheric Research; Geophysical Fluid Dynamics Laboratory; United Kingdom Meteorological Office; National Space Agency and Max-Plank Institut etc.

The equilibrium response experiments considered the steady-state response of the model's climate to a step-function change in atmospheric C02• This would have obvious problems regarding the fact that the outputs should be obtained as time-dependent response. In recent years a few experiments (time-dependent greenhouse gas forcing experiments) have been carried out to improve the models by introducing transient models which would provide information on time-dependent responses. These also suggest that there may be significant differences between the equilibrium and transient responses (Hansen et al., 1988; Bryan et al., 1988).

Scenarios have been developed to analyse future vulnerability of Bangladesh to climate change and sea level rise. For the assessment of vulnerability for Bangladesh four types of scenarios are considered:

• climate change scenarios which would give changed values for different climate parameters (e.g., temperature, evaporation, precipitation etc.) having impacts on the physical events

• socio-economic scenarios providing irrformation on development aspects which would have effects (positive & negative) on the impacts of climate change

• sea level rise scenarios which would give absolute values for changes in sea level at a reference point of time in future

• watershed development scenario which denotes changes in watershed likely to be occurred within the country and beyond the territorial boundary.

For a short time horizon socio-economic changes may be predicted fairly reasonably. Watershed management within the country depends on implementation of development schemes, availability of technical skill, appropriate budgetary provision etc. On the other hand, watershed management outside the country would depend largely on the agreement between the countries within the catchment areas.

CLIMATE CHANGE SCENARIO 15

Sea level rise (SLR) would depend on the rate of change of sea level, as given by IPCC (Houghton et al., 1992). Several studies which have been carried out on impact of sea level rise and climate change in Bangladesh proposed values ranging 15 to 100 em SLR, likely to occur by the year 2100 (Huq et al., 1996; Aluned et al., 1996). For all practical purposes the decadal rate of change in sea level rise given by IPCC may be considered for developing SLR scenarios (Houghton et al., 1996).

Each of the GCM represents a different, highly individu.al solution to the problem of modelling the Earth's climate. There are large inter-model differences in resolution and physics, especially regarding the effects of clouds, sea ice and land surface processes and in the presentation of the ocean. Most GCMs are not capable of handling, as of today, the role of aerosols and particulate matters present in the atmosphere in warming processes. The differences lead to substantial disagreement in the regional details of the equilibrium response to doubled C02 (Schlesinger et al., 1987; Santer et al. , 1990; Gates et al. , 1992). Given the uncertainties about the regional climate change, regional impacts cannot be predicted. However, sensitivities of the systems to climate change can be evaluated by using scenarios of global and regional climate change.

FIGURE 1. Comparative analysis of GCM model outputs with observed data

35

30 ...... ~ e 25 E !'! ., 20 E" ~

I ~Observed --G- CLIM

0 0

~ g. 0 >

Cll 0 ~

I 0 ., a

Note: Observed data refers to the observed time series t emperature values recorded during 1948-1980 at Dhaka station.

The GCM used in this study are supplied by National Center for Atmospheric Research, USA. These include Canadian Climate Centre Model (CCCM), Geophysical Fluid Dynamics Laboratory (GFDL) and Climate Data (CLIM), only for present temperature, to estimate the temperature and precipitation under 1XC02 and 2XC02 conditions and the rate of change in temperature and precipitation (Meehl and Washington, 1989; Wetherald and Menabe, 1986). An attempt has been made to examine the degree of deviation of the GCM output data with respect to the long-time observed data for a particular location of the country. Figure-I shows the comparative status of the model outputs and observed


monthly average temperature (1948 to 1980) data at a particular geographical location which was located approximately at the centre point of the country. The long-time monthly average climatic data were made available from a secondary source (FAO, 1988). It may be noted here that the output of CLIM model is somewhat closer to the observed temperature data set with a variation not exceeding 10 per cent.

In order to develop time dependent climate scenarios, the above mentioned models appear to be ineffective, although they may be used to predict the change in climate at 2XC02

(Hansen et al., 1984;Wilson and Mitchell, 1987) Moreover, the variation of model outputs with respect to the observed values are high, as presented in Figure-1. Therefore, the time independent GCM, namely CLIM, CCCM and GFDL were not used for scenario development.

The transient model GFOl (i.e., Geophysical Fluid Dynamics Laboratory 1% per year transient), on the other hand, provided with information regarding ~ecadal change in climate variables. The model assumes changes of climate parameters due to 1 per cent increase of GHGs per year. For Bangladesh study, GFOl model has been used to reveal average monthly data on temperature and precipitation for the reference year (i.e., 1990, the 4th decade), and for the two projection years (i.e., projection year-1, 2030 and projection year-2, 2075).

2. Estimation Methodology and Results

2.1 TEMPERATURE

The average monthly temperature for the baseyear 1990 (4th decade) and the two projected years 2030 (7th decade) and 2075 (lOth decade) were obtained from GFOl model runs. The relative decadal rate of change in temperature with respect to the baseyear data was calculated. Since the decadal estimates were way off the observed data, those values could not be used as such. Instead, the relative decadal rate of change values were correlated with the corresponding average monthly observed values. These were then compared with the observed values to reveal the absolute change in temperature for the two projection years.

As for example, the temperature for the projection year 2030 was computed by multiplying the relative rate of temperature change from decade-4 to decade-7 with the number of decades which separates the latter decade from the former one. The same method has been applied for all the 10 locations and then the monthly values have been averaged to get annual and seasonal average temperatures.

The observed average monthly temperature values for December, January and February (DJF) and June, July and August (JJA) gave average winter and monsoon temperatures for the baseyear, respectively. The results are summarised and presented in Table-1. Similar average winter and monsoon temperatures for the projection years 2030 and 2075 were


estimated using the estimated monthly average temperature data for the two projection years. The seasonal differences in temperatures for the two years were also estimated, as presented in Table-1. Comparing with the average winter and monsoon temperatures with the baseyear data, the relative changes in temperatures were also estimated, as presented in Table-1.

TABLE 1. Extent of changes in temperature, precipitation and evaporation

Year Average Temperature Average Precipitation Changes in Temperature Increase1 Precipitation Increase2 Evaporation' w M Ave w M Ave w M Ave w M Ave w M Ave

("C) ("C) mm/month mm/month Base 19.9 28.7 25.7 0.0 0.0 0.0 12 418 179 0 0 0 0.6 14.6 83.7 (1990)

2030 21.4 29.4 27.0 1.3 0.7 1.3 18 465 189 +6 47 10 0.9 15.8 83.9

2075 22.0 30.4 28.3 2.1 1.7 2.6 00 530 207 -12 112 28 In f. 135 87.9

Notes: 1) Estimated values obtained by correlating model output data with the observed data. 2) Estimated based on model output data regarding rate of temperature change. 3) Estimated using langs Index and expressed in terms of Aridity Index W stands for winter, M stands for monsoon, Ave stands for average and Inf stands for infinity

The calibrated future temperature of Bangladesh shows that the average increase of temperature would be 1.3°C and 2.6°C for the year 2030 and 2075, respectively. The results also show the seasonal variation of the temperature i.e. 1.3°C in the winter and 0.7°C in the monsoon for the year 2030. Similar temperature changes for the year 2070 would be 2.1°C and 1.7°C for the two seasons, respectively. The monthly average temperatures for the three years are presented in Figure-2.

FIGURE 2. Changes in mean monthly temperature

35.00 33.00

G 31.00 0 29.00 ~ a 27.00 r: <I) 25.00 s "' 23.00 f-< § 21.00 "' ::E 19.00

1- - -tr . - 1990 --<>- 2030 --o- 2075 1

17.00 15.00

Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec


The results also reveal that there is a general increasing trend regarding temperature. In 2030, the increase is much pronounced in winter months, although the maximum change is observed for post-winter months, i.e., April, May and June. However, in 2075, the increase in temperature during April and May is much higher; about 4.0°C.

2.2. PRECIPITATION

Same method, as in the case of temperature, has been used to estimate future precipitation change for Bangladesh and presented in Figure-3. The results show that precipitation in 2030 will increase slightly in winter and moderately in monsoon. In 2075, however, the change is much pronounced in monsoon (about 112 mm/month), while there would not be any appreciable winter precipitation.

FIGURE 3. Changes of average precipitation

700 .----------------------

600

500

400

300

200

100

l I

I

I

Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec

- - <> . -1990 ~ 2030 --a- 2075

2.3. EVAPORATION

Potential evaporation is a function of temperature and is expressed in terms of Lang's Index of Aridity, I = PIT, indicating that the effectiveness of precipitation varies directly with precipitation and inversely with temperature (Trewartha, 1968). Similar relations are given by De Martonne's moisture index, I= P/(T + 10), and Koppen's index I= P/(T + 7); both of which are modifications of Lang's Index.


The changes in evaporation were computed by using Lang's index of aridity. The results are presented in Table-1. From the results it is revealed that the average evaporation would be almost similar in 2030 and slightly higher in 2075 compared to that of 1990 values. But in winter months (December to March) evaporation for 2075 would be much higher owing to less precipitation, which would decrease moisture availability in dry months. Even in monsoon months evaporation would be much higher in 2075. All these results suggest that there would be extreme events in monsoon and winter, while the average annual change in evaporation would be insignificant.

3. Conclusions

GCM outputs in combination with the observed time-series data reveal that there would be more precipitation in the monsoon while winter precipitation would decrease considerably. Increased rainfall runoff would inundate low-lying lands and might cause drainage congestion leading to severe floods. The situation would become more grave in 2075 compared to that in 2030.

Low precipitation and higher temperature in winter months would cause higher probability for drought to occur. This might have severe consequences on foodgrain production in Bangladesh.

The present analysis did not consider the changes in abundance of day-time solar radiation. Any such change has significant consequences on foodgrain production. This may be looked into in future.

It is found that, there would be drastic changes in evaporation in both winter and monsoon seasons in the year 2075. Evaluating the changes of climatic parameters under the projection years with respect to the baseyear situations, one might imply that the changes in 2030 would be moderate while those in 2075 would be high.

References

Ahmed, A.U., Huq, S., Karim, Z., Asaduzzaman, M., Rahman, A.A., Alam, M., Ali, Y. and Choudhury, R.A., 1996. Vulnerability and Adaptation Assessment for Bangladesh. In Vulnerability and Adaptation to Climate Change, J.B. Smith, S. Huq, S. Lenhart, L.J. Mata, I. Nemesova and S. Toure (Eds.).Kluwer Academic Publishers, Dordrecht, pp. 141-159.

Bryan, K., Menabe, S. and Spelman, M.J., 1988. Interhemispheric asymmetry in the transient response of a coupled ocean-atmosphere model to a C02 forcing. Journal of Physical Oceanography 18, 851-867.

FAO, 1988. Land Resources Appraisal of Bangladesh for Agriculiure Development, Report 3: Land Resource Data Base, Volume 1: Climatic Data Base, United Nations Development Programme/Food and Agriculture Organisation of the United Nations, 1988.


Gates, W.L., Mitchell, J.F.B., Boer, G.J., Cubasch, U. and Meleshko, V.P., 1992. Climate Modelling, Climate Prediction and Model Validation. In J.T. Houghton, B.A. Callander and S.K. Varney (Eds.), Climate Change 1992: The Supplementary Report to the IPCC Scientific Assessment. Cambridge University Press, Cambridge, pp. 97-134.

Hansen, J., Lacis, A., Rind, D., Russell, G., Stone, P., Fung, I., Ruedy, R. l!fld Lerner, J., 1984. Climate Sensitivity: Analysis of feedback mechanisms. In Climate Processes and Climate Sensitivity J. Hansen and T. Takahashi (Eds.), Maurice Ewing Series 5, American Geophysical Union, Washington D.C., 368 pp.

Hansen, J., Fung, I., Lacis, A., Rind, D., Lebedeff, S., Ruedy, R. and Russell, G., 1988. Global climate changes as forecast by Goddard Institute for Space Studies three-dimensional model. Journal of Geophysical Research 93, 9341-9364.

Houghton, J.T., Callander, B.A. and Varney, S.K. (Eds.), 1992. Climate Change 1992: The Supplementary Report to the IPCC Scientific Assessment. Cambridge University Press, Cambridge.

Houghton, J.T., Meira Filho, L.G., Callander, B.A., Harris, N., Kettenberg, A. and Maskell, K. (Eds.), 1996. Climate Change 1995: The Science of Climate Change. Cambridge University Press, New York.

Huq, S., Ahmed, A.U. and Koudstaal, R., 1996.Vulnerability of Bangladesh to Climate Change and Sea Level Rise. In Climate Change and World Food Security, T.E. Downing (Ed.), NATO ASI Series, 137, Springer-Verlag, Berlin, Hiedelberg, 1996. pp. 347-379.

Meehl, G.A., and Washington, W.M., 1989. Climate sensitivity due to increased C02: experiments with a coupled atmosphere and ocean general circulation model. Climate Dynamics 4, l-38.

Santer, B.D., Wigley, T.M.L., Schlesinger, M.E. and Mitchell, J.F.B., 1990. Developing Climate Scenarios from Equilibrium GCM Results. Report No. 47, Max-Plank Institut, Hamburg, March 1990.

Schlesinger, M.E. and Mitchell, J.F.B., 1987. Climate Model Simulations of the Equilibrium Climatic Response to Increased Carbon Dioxide. Reviews of Geophysics 25, 76Q-798.

Strezepek, K.M. and Smith, J.B., 1995. As Climate Changes: International Impacts and Implications, Executive Summary, K. M., Strzepek and J. B., Smith (Eds.), Cambridge University Press, 1995.

Trewartha, G.T. An Introduction to Climate. Fourth Edition, McGraw-Hill, Inc., pp 370-391.

Wetherald, R.T. and Menabe, S., 1986. An investigation of cloud cover change in response to thermal forcing. Climate Change 8, 5-23.

Wilson, C.A. and Mitchell, J.F.B., 1987. Doubled C02 climate sensitivity experiment with a global climate model including a simple ocean. Journal of Geophysical Research 92, 13315-13343.

WATER RESOURCES VULNERABILITY TO CLIMATE CHANGE WITH SPECIAL REFERENCE TO INUNDATION

MOZAHARUL ALAM Research Fellow Bangladesh Centre for Advanced Studies (BCAS)

AIN-UN NISHAT Professor Bangladesh University of Engineering and Technology (BUET)

SAAD M. SIDDIQUI Associate Specialist Surface Water Modelling Centre (SWMC)

ABSTRACT

Vulnerability of water resources considered changes in flooding conditions due to combination of increased discharge of river water during monsoon period and sea level rise for the two projection years, 2030 and 2075. MIKEll, a fzxed bed hydrodynamic model, was used for the estimation of changes in river water level which was coupled with Geographic Information System (GIS) for the estimation of extent of flooding. The climatic parameters for the baseyear 1990 was obtained from secondary sources and the changes of climatic parameters for the two projection years were obtained from the General Circulation Model (GCM) output. Values of these parameters were taken as input for MIKEll model runs. Discharge values for 8 upstream boundary stations were calculated from a general relationship between changes in rainfall and runoff. The MIKEll model also includes other parameters under development scenario that considered embanking the major rivers. Model runs gave water level values for over 4,000 output stations along the rivers all over the country except Chittagong and Chittagong Hill Tracts area. These water levels were interpolated by using GIS techniques to generate water depth spatial database for the study area. Water depth spatial database for each of the projection years was compared with that of the baseyear to find change in water depth. These values were then superimposed on "land type database" to estimate extent of flooding in terms of water depth. A combination of development and climate change scenarios revealed that the Lower Ganges and Surma floodplains would become more vulnerable compared to the rest of the study area. On the other hand, the north-central region would become flood free due to embankment in the major rivers.

21

22 M. ALAM, A. NISHA T and S.M. SIDDIQUI

1. Introduction

Bangladesh's surface water and groundwater resources play vital roles in agricultural, forestry, fisheries and livestock production. They also play significant roles in settlement, domestic water supply and communications and indirectly in sanitation and health. Differences in depth and duration of seasonal flooding on different soil and land types strongly influence the kinds of crops and cropping rotations. Accordingly, any change in these water resources caused by climate change and sea level rise could have additional impacts on agricultural, fisheries, forestry and livestock prqduction as well as domestic and industrial water uses and water communications.

Bangladesh Climate Change Country Study considered vulnerability and adaptation assessment, among others, for the water resources sector. In supply side, water resources sector deals vulnerability of the following sub-sectors under the different combination of climate change and sea level rise options:

a) Changes in river water level in monsoon which would reflect the change in depth of inundation.

b) Salinity intrusion due to sea level rise and low water flow from upstream during the winter.

In the demand side, water resources sector deals vulnerability of the following subsectors under the different combination of climate change and sea level rise options:

a) Changes in soil moisture would reflect the changes in drought situation, and

b) Changes in groundwater level or groundwater fluctuation.

Information on the supply side of the above mentioned sub-sectors, specially information on river water level, have been obtained by using a fixed bed one dimensional surface water simulation model named MIKEll Hydrodynamic Model.

It assumed that the river water level would change due to changes in upstream river discharge, backwater effect of sea level rise and confinement effect of flood protecting infrastructure. Moreover, the country being located on a geotectonically active sedimentary basin, it experiences subsidence almost all over the delta. Subsidence of land, however, not only affects the mean sea level, it might result in changes of water level as a relative measure over the surrounding lands and thus in the depth of inundation.

The changes in river water level due to the above mentioned circumstances have been considered, separately and in combination, for the projection years 2030 and 2075, respectively. Only the combined impact on inundation has been analysed and presented here.

VULNERABILITY OF WATER RESOURCES 23

2. Methodology

One dimensional fixed bed surface water simulation model was used for the assessment of changes of river water level assuming that the depth of inundation is a function of river water stage and local precipitation. The fluctuation of river water stage depends on mainly upstream river discharge, confmement of river courses and backwater effect of sea water. MIKE11 1 Regional and General Models were run with respect to climate change and sea level rise condition, which have profound impacts on river water stage. The model runs provided river water level and river discharge for the year 1990 as baseyear and 2030 and 2075 as two projection years.

The climatic parameters for the baseyear 1990 was obtained from the secondary sources and the changes of climatic parameters for the two projection years were obtained from the General Circulation Model (GCM) output (Ahmed and Alam, 1998). Table-1 shows the fluctuations of values of the parameters considered with respect to their values under baseyear situations.

TABLE 1. The fluctuations of values of the parameters considered with respect to their values under baseyear situation

Parameters 2030 2075 Winter Monsoon Winter Monsoon

Temperature ("C) 2 0.65 3 1.5 Evaporation(%) 10 2 16 5 Precipitation(%) -3 II -37 28 Discharge(%) -5 20 -67 51 Watershed 60 100 development(%) Sea level rise (em) 30 70

Note: Base simulation run of the model has been performed under the present climate condition and assuming no sea level rise Source: Adapted from Ahmed et al., 1996

Besides these, watershed development, inside the country, for the year 2030 and 2075 have also been incorporated in the simulation models. For simplicity of model runs, it was assumed that 60 per cent and 100 per cent of all proposed embankment projects considered/ proposed under the Flood Action Plan (F AP) along the major rivers (e.g. the Jamuna and the Ganges) will be implemented by the year 2030 and 2075, respectively. Figure-1 shows the embankment considered in model runs. Future changes in discharge for 8 upstream boundary stations (QFs), shown in Figure-1, have been calculated from the relationship between changes of rainfall and changes in runoff. It is found that a consistent trend of response of runoff change exists due to rainfall change with an approximate linear slope of 1.83 for the north-west region, which is relatively

1 One dimensional fixed bed surface water simulation model developed by Danish Hydraulic Institute (DHI), Denmark.

24 M. ALAM, A . NISHA T and S.M. SIDDIQUI

FIGURE 1. Schematic representation of river network with MIKE II boundary station and

considered embankment

-···~

I Dl

LEGEND

~Rivers

International Boundary

- - Embankment

QF & HF Boundary Stations

0 50

INDIA

Bay of Be11gal

N

w-<?• KM

100 150 200

' '


less with respect to the other northern regions (ADB, 1994). The changes in upstream river discharge were calculated based on rainfall-runoff relationship of north-west region. Figure-2 shows the rainfall-runoff relationship of the north-western region of the country.

FIGURE 2. Relationship between changes of runoff and rainfall for northwest region of Bangladesh

.. .. '"

100

.::· e 5 80

.; -~ '" = 60

::: " c = 40 !>: .:: .. ... c 20 .. .c u c .. ... .. .. I>< -20

X

X

X

v

0 0

20

0 X

"" v

v

.o.Q --183 .o.R .

1987-1988 Data J 1988- 1989 Data 1987- 1988 Data 1988- 1989 Data

% Change has been Calculated Based on 1986-87 Data

40 60

J Area Type · l

Area Type- 2

80 100

Percent Change in Rainfall Data (mm/year)

From information regarding river water level of the output stations, as provided by the Model, a water depth spatial database was generated for the baseyear, 1990 and the two projection years 2030 and 2075, respectively. It was done by the use of raster based GIS techniques. Water depth spatial database for each of the projection years was compared with that of the baseyear to fmd change in water depth. Spatial database for water depth change was then categorised into ten classes. These values were then superimposed on "land type database" to estimate extent of flooding in terms of water depth according to a land type change matrix. Changes in land types from one class to the other were estimated by GIS overlaying methods for each projection year.

3. Description of MIKEll Model

MIKEll hydrodynamic model has several independent modules, calibrated for the river systems of Bangladesh. The General Model includes the three major rivers - the Ganges, the Brahmaputra (Jamuna) and the Meghna and a number of other large rivers covering the main drainage system of the country. There are six regional models, each of which independently covers the drainage systems of the six regions of the country (SWMC, 1998). A brief description of the models is presented here.

26 M. ALAM, A. NISHAT and S.M. SIDDIQUI

3.1 GENERAL MODEL

The General Model is based on the hydrodynamic module and the rainfall-runoff module of the MIKEll system. The general model was one of the first models developed at Surface Water Modelling Centre (SWMC) situated at Dhaka, Bangladesh, during the period of 1986-90. This model simulates the unsteady flow in the main rivers of Bangladesh. It has 8 stations of incoming rivers (QFl to QF8) and 6 stations where the rivers discharge in the Bay of Bengal (HFl to HF6). Locations of both incoming and discharge stations of MIKE 11 model are shown in Figure-1.

The General Model is thoroughly calibrated and verified for the period 1986-1991, that includes the two years of disastrous floods in Bangladesh, 1987 and 1988. SWMC has been constantly verifying the performance of the model with the latest available data (SWMC, 1992).

The model has been extensively used on water planning applications in the country. The most recent use of this model is in the Flood Hydrology Study component of Flood Action Plan (FAP, Project No. 25). The General Model is also run by Bangladesh's Flood Forecasting and Warning Centre (FFWC) on a routine basis to generat.e flood level maps for flood forecasting during the monsoon season.

3.2 REGIONAL MODELS

Along with the General Model, a series of five more regional models cover the entire country in greater details. Each regional model accommodates enormous volume of topographic and hydrometric data.

All regional models are calibrated against at least 2 years of observed data. Validation of the models against most recent data was carried out by SWMC on an annual basis. Recently, these models have been used by the national FAP for carrying out water resources planning investigations at pre-feasibility and feasibility stages.

4. Assumptions for Model Runs

Changes in river water levels would cause changes in sediment carrying capacity of the rivers. As a result, bed levels of the rivers would be changed. Decreased water level gradients due to higher downstream water levels at sea result in lower flow velocities and consequently cause sedimentation in the river bed. The morphologically highly dynamic rivers in Bangladesh are expected to adapt to such changes in water levels in a long period of time. These changes in bed levels in turn would cause additional changes in river levels, the effect of which will propagate the impact of sea level rise in upstream direction. First assessment of this effect in the study for the Jamuna Bridge showed the importance of this feed back mechanism (Rende! et al., 1990).


Based on the above morphological issues the following approach was taken into account for assessing the river water level:

• Subsidence and Sedimentation were not considered in the model run partly because of the uncertainty of the magnitude of its value and partly because of its local variability (BCASIRA/Approtech, 1994).

• Computation of river water level for 1990 as a baseyear and 2030 and 2075 as projected years was done assuming no changes in river bed.

• Output of MIKE II was not adjusted further with the bed level change of the river due to its uncertainty in magnitude and local variability.

5. Creation of Water Depth Spatial Database for the Year 1990, 2030 and 2075

MIKEll model runs provided river water level information for all available river crosssections for the year 1990 as baseyear and two projection years 2030 and 2075, respectively. Water level information of all cross-sections was linked up with its respective geographic location through database management system. From the linked database, all cross-sections were identified and created a cross-sections location coverage using ARC/INFO, a widely used Geographic Information System (GIS) module. Location of cross-sections and their associated water level information were then converted into another GIS software namely IDRISI, a raster based GIS system, for further analysis.

Water depth spatial databases were generated based on location of cross-section and river water level through the Interpolation Module of IDRISI for the base and two projection years. The following options were taken into account to run.IDRISI Interpolation Module:

• Interpolate a Digital Elevation Model by means of a distance-weighted average, and

• Interpolate water level for each point considering the 6 nearest diverging points because of the fact that the locations of all crosssections are not evenly distributed.

Spatial database of water depth for the baseyear was then subtracted from those for each of the projection years to ascertain the changes of water levels. The changes in water level were categorised into ten classes. Table-2 shows the classification of the water levels.

6. Assumptions for Assessment of the Changes of Land Type

Changes of land type from one class to other due to changes in flooding conditions were analysed for the two projection years 2030 and 2075, respectively. A land type

28 M. ALAM, A. NISHATand S.M. SIDDIQUI

database was created by the Master Planning Organization (MP02) based on inundation depths. The database has been transformed into a spatial digital inundation database by Irrigation Support Programme for Asia Near East (!SPAN, 1994). The same database has been used for the present study as the reference year database. Intermediate flood depth classes were merged with parent classes evenly. Protected and unprotected areas of the country were not taken into account. Since settlement and agricultural activities in the Sundarbans area are insignificant with compared to that for other areas, the changes in flood area were not determined for the Sundarbans. All changes were calculated based on the land type change matrix.

TABLE2. Classification of water levels

Class Changes in water level Averaged water level (m) (m)

I >- 3.60 -4.40 2 - 3.60 to- 1.80 -2.70 3 - 1.80 to- 0.90 - 1.35 4 - 0.90 to - 0.30 -0.60 5 - 0.30 to - 0.00 -0.15 6 0.00 to 0.30 0. 15 7 0.30to 0.90 0.60 8 0.90 to 1.80 1.35 9 1.80 to 3.60 2.70 10 >3.60 4.40

Relative vulnerabilities regarding the changes of land types from one class to the other, the following terms have been used: extremely vulnerable, moderately vulnerable and slightly vulnerable. Changes of FO and Fl lands to the F2 land have been termed as extremely and moderately vulnerable, respectively. Change of FO land to the Fl land has been termed as slightly vulnerable. In addition, changes of FO and Fl to the F3F4 also termed as extremely vulnerable. Detail of MPO land type and land type change matrix are presented below.

6.1. MPO LAND TYPES

In order to evaluate the potential land in terms of the nature and depth of annual flooding, the Master Plan Organization (MPO) has formulated a framework of flood depth distribution through a classification of land types according to flood depth (MPO, 1990). This is the first and most reliable national land type database uses in any analytical job and national policy planning issues. Under the activity of Flood Action Plan, MPO land type database was converted into the digital format spatial database. All further analysis made was based on it. Details ofMPO land type classification are presented in the Table-3.

2 The Master Planning Organization was a strategic planning wing of the Government of the People's Republic of Bangladesh. The MPO land type classification was introduced considering inundation criteria of lands during monsoon.


TABLE3. MPO land types

Land Type Description Flood Depth (em) Nature of Flooding

FO Highland < 30 Intermittent F1 Medium high land 30-90 Seasonal F2 Medium low 90- 180 Seasonal F3 Lowland 180- 360 Seasonal F4 Low to very low >360 Seasonal/perennial

6.2. LAND TYPE CHANGE MATRIX

From the MPO land type database, a logarithmic trend line was drawn to calculate the amount of land in an intermediate depth of inundation. The logarithmic trend of various land types is shown in Figure-3.

Based on the logarithmic trend, a land type change matrix was established to calculate the changes of land from one class to other. Table-3.1 to 3.5 show the land type change matrix.

FIGURE 3. Logarithmic trend ofland types

120.000 , ---,----,--T I I

...-:. 00 0 N o:"') lt) 00 0

-Depth in em'

TABLE 3.1. Land type change matrix for FO land (0-30 em)

Average Change New Depth oflnundation New Land Type -440 em -440 to -410 em FOland (100%) -270 em -270 to -240 em ~0 land (100%) - 135 em -135 to -105 em FOland (100%) -60 em -60 to -30 em FOland (100%) - 15 em -15 to +15 em FOland (100%) +15cm +15 to +45 em FO (86%) & F1(14%) +60em +60 to +90 em F1 land (100%)

+ 135 em +135 to+l65 em F21and (100%) + 270 em +270 to +300 em F3 land (100%) + 440 em +440 to +470 em F4land (100%)


TABLE3.2. Land type change matrix for F1 land (30-90 em)

Average Change New Depth oflnundation New Land Type -440 em -410 to -350 em FOland (100%) -270 em -240 to -180 em FO land ( 100%) - 135 em -105 to -45 em FO land ( 100%) -60 em -30 to +30 em FOland (100%) - 15 em +15 to +75 em FO (67%) & Fl (33%) +15cm +45 to +105 em Fl (83%) & F2 (17%) +60cm +90 to +150 em F2 land (100%)

+ 135 em + 165 to_ +225 em F2 (69%) & F3 (31 %) + 270 em +300 to +360 em F3 land ( 100%) + 440 em +470 to +530 em F4land (100%)


Average Change New Depth of Inundation New Land Type -440 em -350 to -260 em FOland (100%) -270 em -180 to -90 em FOland (100%) - 135 em -45 to +45 em FO (86%), Fl (14%) -60 em +30to+l20cm Fl (87%), F2 (13%) - 15 em +75to+165cm Fl (44%), F2 (56%) +15cm +105to+l95cm F2 (87%), F3 (13%) +60cm +150to+240 em F2 (62%), F3 (38%)

+135cm +225 to +315 em F3 land ( 100%) + 270 em +360 to +450 em F4 land (I 00%) + 440 em +530 to +620 em F4 land (100%)


Average Change New Depth oflnundation New Land Type -440 em -260 to -80 em FO land ( 100%) -270 em -90 to +90 em FO (62%), Fl (38%) - 135 em +45 to +225 em Fl (57%), F2 (43%) -60 em +120 to +300 em F2 (69%), F3 (31 %) - 15 em +165 to +345 em F2 (44%), F3 (56%) +15cm +195 to +375 em F3 land (100%) +60 em +240 to +420 em F3F4

+ 135 em +315 to +495 em F3F4 + 270 em +450 to +630 em F4 land (100%) + 440 em +620 to +800 em F4 land (100%)

7. Assessment of the Changes of Land Types

Assessment of water resources vulnerability considered changes in flooding conditions

due to combined circumstances of increased river discharge during monsoon period,

confinement of river course and backwater effect of sea level rise for the two projection

years, 2030 and 2075, respectively. Details assessments of the changes of land type

from one class to other are presented here including the status of the present land type.


TABLE 3.5. Land type change matrix for F4land (> 360 em)

Average Change New Depth of Inundation New Land Type -440 em -80 to NP FOland (100%) -270 em +90 to NP F2 land (100%) - 135 em +225 to> 360 em F4 land (100%) -60cm +300 to> 360 em F4 land (100%) - 15 em +345 to> 360 em F4 land (100%) +15cm > 360 em F4 land (100%) +60cm >360 em F4 land (100%)

+ 135 em > 360 em F4land (100%) + 270 em > 360 em F4land (100%) +440 em > 360 em F4land (100%)

7.1. EXISTING (1990) LAND TYPE AND AREA

As mentioned earlier that the present study considered the inundation depth database where the country was categorised into thirteen classes based on flood depths and physical features. Existing land areas, according to depths of inundation, are given in Table-4 that excludes areas under river courses and estuaries. Figure-4 shows the spatial distribution of the existing (1990) land types.

TABLE4. The existing (1990) land area by land types (in sq. km)

Land Type Existing Outside study Area

FOland 56,770 13,710

FO + F1land 1 1,570 386

F1land 32,965 979

F1+ F2land 2 320 60

F2land 16,182 610

F2 + F3 + F4land 3 365 3

F3F4land 14,090 14

Urban area 4 900 143

River bank/sand bar etc. 3,260 1,721

Forest (SB) + others 5,650 104

Mixed land 3,200 3,022

No data 1,615 968

Total 136,887 21,720

Country total 144,000

Notes: SB means the Sundarbans 1 It assumes that the total/and comprises of 50% FO and 50% Fl land. 1 It assumes that the total/and comprises of 50% F 1 and 50% F2 land.

Study area

43,060

1,184

31,986

260 15,572

362

14,076

757 1,539

5,546

178

647

115,167

144,000

3 It assumes that the total/and comprises of 35% F2 and remaining is F3F4 land. 4 Urban areas were merged with the FO land except Chittagong city area

Source: !SPAN GIS database

Generalised Area

44,409

32,708

15,829

14,311

1,539 5,546

178

647

115,167

144,000

32 M. ALAM, A. NISHA T and S.M. SIDDIQUI

FIGURE 4. Spatial distribution of existing land types

LEGEND

l Ji1J land II Urban area

~ Ji1J+Fl land ~ Mixed land F1 land lJ o dat.a f'l+F2 l~nd Sand Bar elc. F2 land ;~ Foresl Land F2+FJt F4 land

I DIA

Bay of Bengal


7.2. LAND TYPE AND AREA IN 2030

The changes in flood depth areas were calculated through the GIS analysis. It found that 8 per cent and 1 per cent (i.e. 3612 sq. km and 396 sq. km) of existing FO and F1 land would become extremely vulnerable, respectively. Analysis also showed that 54 per cent (i.e. 17672 sq. km) of F1 land would become moderately vulnerable and 36 per cent of existing FO and 32 per cent of existing F2 land would become slightly vulnerable in 2030. Moreover, 14 per cent of Fl land, 16 per cent of F2 land and 15 per cent of F3F4 land would virtually become FO land due to the fact that embankment would make certain area flood free. Considering all types of changes from one class to the others, the country will lose 24 per cent ( 10726 sq. km) of FO land and 19 per cent (i.e. 6263 sq. km) ofFlland. On the other hand 13601 sq. km land will be added to the existing F2 land. Details of the results are presented in Table-5. Changes of land types are presented in Figure-6.1 to 6.4 and the spatial distribution of land types in 2030 is shown in Figure-5.

TABLES. Changes of land from one class to the others in 2030 (in sq. km)

Land Type Study Area Transformed in 2030

FO FO+F1 1

Fl Fl + F22

F2 F2 + F3 + F43

F3F4 Urban area4

River bank/sand bar etc. Forest Mixed land No data Total Notes:

43,060 1,184

31,986 260

15,572 362

14,076 757

1,539 5,546

178 647

115,167

Forest means the Sundarbansforest area

FO F1 F2 F3F4 23,415 16,033 3,442 170

592 592 4,399 9,519

2,440

2,080 757

130 162

9

17,672 130

7,903 127 155

396

5,067 235

11,836

33,683 26,445 29,429 17,700

'·4 Same assumptions have been considered as in Table-4.

7.3. LAND TYPE AND AREA IN 2075

Analyses of changes in inundation levels for the year 2075 suggested that substantial changes would occur both in negative and positive sense. It was found that 16 per cent (i.e. 7267 sq. km) of existing FO and 7 per cent (i.e. 2354 sq. km) of existing Fl land would become extremely vulnerable. About 54 per cent (i.e. 17585 sq. km) of existing Fl land would become moderately vulnerable and 36 per cent (i.e. 16203 Sq. Km.) of existing FOland would become slightly vulnerable by the year 2075. In addition, 25 per cent of existing Fl, 30 per cent of existing F2 and 22 per cent of existing F3F4 land would virtually become FO land due to the fact that embankment would make certain area flood free. Changes in land types are presented in Figures-6.1 to 6.4.

34 M . ALAM, A. NISHA T and S.M. SIDDIQUI

FIGURE 5. Spatial distribution of land types in 2030

LEGEND PO la nd • Urban area

~ POt fl land ~ Mixed land F1 land L No data F'l+F2 land • Sand Bar elc. F2 land .. , Forest Land F2t F3tF4 land

INDIA

Bay of Bengal


FIGURE 6.1. Changes of FOland in different projection years

45000

40000 l

~ 35000 I

30000 .;.

25000 C/)

c 20000

" 15000 ~ <( 10000

5000 0

FO FO Fl F2 F3F4

Land Types

FIGURE 6.2. Changes of Fl land in different projection years

35000

30000 E 25000 :.:: & 20000

C/)

c 15000 l

" .. 10000 ~

5000

0

Fl FO Fl F2 F3F4

Land TyllCS

FIGURE 6.3. Changes of F2 land in different projection years

16000 14000

E 12000 :.:: 10000 &

rJ) 8000 c

" 6000 " .. 4000 <(

2000 0

F2 FO Fl F2 F3F4

Land TyllCS


FIGURE 6.4. Changes ofF3F4 land in different projection years

16000

14000 j e 12000

::.:: Q- 10000

"' c 8000

'"' 6000 .. ,_ 4000 < 2000

0

F3F4 FO Fl F2 F3F4

Land Types

Considering all types of changes from one class to the others, it was. found that 16 per cent (7764 sq. km) of FO land and 34 per cent (i.e. 1194 sq. km) of F1 land would be submerged in monsoon. On the other hand 12345 sq. km land will be added with the existing F2 land. Detailed results are presented in Table-6. The spatial distribution of land types for 2075 is shown in Figure-7.

TABLE6. Changes of land from one class to the others in 2075 (in sq. km)

Land Type Study Area Transformed in 2075

FO Fl F2 F3F4

FO 43,060 19,588 16,203 6,730 537

FO+Fl 1,184 592 592

Fl 31,986 7,884 4,160 17,589 2,354

Fl +F2 260 130 130

F2 15,572 4,735 429 3,552 6,857

F2 + F3 + F4 362 127 235

F3F4 14,076 3,088 46 10,946

Urban area 757 757

River bank/sand bar etc. 1,539

Forest 5,546

Mixed land 178

No data 647

Total 115,167 36,644 21,510 28,174 20,929 Notes:

Forest means the Sundarbans forest area ' ·' Same assumptions have been considered as in Tab/e-4.


FIGURE 7. Spatial distribution of land types in 2075

LEGEND

:-1 F'O land Urban area ~ FO+Fl land ~ Mixed land

F1 land ~ No data Fl+F2 land Sand Bar etc. F2 land rm Forest Land F2tP3+F4 land

INDIA

Bay of Bengal


8. Conclusions

Water resources vulnerability to climate change, confinement of river course and sea

level rise induced backwater effect was examined for the years 2030 and 2075,

respectively, with reference to the existing depth of inundation. Extreme impact was

found for FOland followed by Fl land and moderate and slightly impact was found for

Fl and FO lands, respectively, during the period of 2075 where embankment played an

important role in restricting the extent of flood affected areas. Op. the other hand,

extreme impact was found for FO land followed by Fl land in 2030 where only the

north-central region was considered to be under the protection of embankment.

A combination of development and climate change scenarios revealed that the Lower

Ganges and the Surma floodplain would become more vulnerable compared to the rest

of the study area. On the other hand, the north-central region would become flood free

due to embanking the major rivers.

References

ADB, 1994. Climate Change in Asia: Bangladesh Country Report. Asian Development Bank

Ahmed, A.U. and Alam, M., 1998. Development of Climate Scenarios with General Circulation Models, In Vulnerability and Adaptation to Climate Change for Bangladesh. S. Huq, Z. Karim, M. Asaduzzaman and F. Mahtab (Eds.), Kluwer Academic Publishers, Dordrecht, The Netherlands. pp. 13-20.

BCAS/RA/ Approtech, 1994. Vulnerability of Bangladesh to Climate Change and Sea Level Rise:

Concepts and Tools for Calculating Risk in Integrated Coastal Zone Management. Technical Reports Volumes I and II, Summary Report and Institutional Report. Bangladesh Centre for Advanced Studies (BCAS), Dhaka, Bangladesh.

MPO, 1990. Surface Water Availability, Technical Report No. 10. Master Plan Organization, Government of Bangladesh, Dhaka, Bangladesh.

Rende! Palmer and Tritton, Nedeco and BCL, 1990. Jamuna Bridge Project Design Report.

Volume II. Feasibility Report, Jamuna Bridge Project - Phase II Study, People's Republic of Bangladesh, World Bank and United Nations Development Programme.

SWMC, 1992 General Model Verification Report. Surface Water Modelling Programme Phase II. Master Plan Organization, Surface Water Modelling Centre; Ministry of Irrigation, Water Development and Flood Control, Government of Bangladesh.

SWMC, 1998. Report on General and Regional Models. Surface Water Modelling Centre, Dhaka, Bangladesh.

ISPAN, 1994. Report on National Database, Irrigation Support Programme for Asia Near East, Flood Protection and Control Organization, Dhaka, Bangladesh.

CLIMATE CHANGE VULNERABILITY OF CROP AGRICULTURE

ZAHURUL KARIM Executive Chairman Bangladesh Agricultural Research Council (BARC)

SK. GHULAM HUSSAIN Principal Scientific Officer Bangladesh Agricultural Research Council (BARC)

AHSAN UDDIN AHMED Senior Specialist Bangladesh Unnayan Parishad (BUP)

ABSTRACT

A simulation study was conducted to assess the vulnerability of foodgrain production due to climate change in Bangladesh. Two general circulation models were used for development of climate scenarios. The experiments considered impact on three high yielding rice varieties and one high yielding wheat variety. Sensitivity to changes in temperature, moisture regime and carbon-di-oxide fertilisation was analysed against the baseline climate condition.

The GFDL model predicted about 17 per cent decline in overall rice production and as high as 61 per cent decline in wheat production compared to the baseline situation. The highest impact would be on wheat followed by A us variety. CCCM model predicted a significant, but much reduced shortfall in foodgrain production.

It was found that increase in 4°C temperature would have severe impact on foodgrain production, especially for wheat production. On the other hand, carbondi-oxide fertilisation would facilitate foodgrain production. A rise in temperature cause significant decrease in production, some 28 and 68 per cent for rice and wheat, respectively. On the other hand, doubling of atmospheric concentration of C02 in combination with a similar rise in temperature would result into an overall 20 per cent rise in rice production and 31 per cent decline in wheat production. It was found that Bora rice would enjoy good harvest under severe climate change scenario.

The apparent increase in yield of Bora and other crops might be constrained by moisture stress. A 60 per cent moisture stress on top of other effects might cause as

39

40 Z. KARIM, S.G. HUSSAIN and A.U. AHMED

high as 32 per cent decline in Boro yield, instead of having an overall 20 per cent net increase. It is feared that moisture stress would be more intense during the dry season, which might force the Bangladeshi farmers to reduce the area for Boro cultivation. Shortfall in foodgrain production would severely threaten food security of the poverty ridden country.

1. Introduction

There is no denying the fact that, the climate system is changing across the globe. This change is attributed to the net effect of individual and interactive effects of changes in atmospheric composition, land use, biological diversity, and climate (Walker and Steffen, 1997). Many natural ecosystems are also likely to change as a consequence of climate change. Since climatic factors strongly interact to affect crop yields, it is likely that climate change will affect crop production. The question remains: how much, where and whether the effect would be positive or negative.

There have been many studies to assess the impact of climate change on crop production on sub-regional, regional and global levels. Models have provided an important means for integrating many different factors that affect crop yield over a cropping season (Rosenzweig and Iglesias, 1994; Rosenzweig and Parry, 1994; IBSNAT, 1989). But modelling outputs often do not tally with each ether due to multidimensional complications. No model, as yet, has been developed that enable one to predict the overall impacts of climate change on crop production with certainty. However, with the present level of understanding one may conclude by saying that, on the whole, the global agricultural production will not suffer much due to the impacts of climate change, but the regional effects will vary widely (for an overview see Reilly et al., 1996).

It is believed that climate change would increase the disparities in cereal production between developed and developing countries. The production in the developed world would benefit from climate change, while that in developing nations would decline (Walker and Steffen, 1997). Farm-level adaptation would be inadequate in reducing the disparities. It is also reported that even an extensive farm-level adaptation in the agricultural sector would not entirely prevent such negative effects. In general, the tropical and subtropical countries would be more vulnerable to the potential impacts of global warming through effects on crops, soils, insects, weeds and diseases. On the other hand, elevated carbon-di-oxide (C02) concentrations will have beneficial effects on crop production. This article analyses how impacts of climate change would cause enhanced vulnerability to the crop production systems in Bangladesh.

2. General Vulnerability of Crop Agriculture in Bangladesh

Crop agriculture vulnerability is common in Bangladesh and observed in many different ways. The important elements are flood, flash-flood, drought, salinity intrusion, organic

VULNERABILITY OF CROP AGRICULTURE 41

matter depletion, low-flow condition of surface water systems etc. All such physical effects have profound interactions with soil and diffusion of nutrients, micro-nutrients and water from soil to plant at the root zones.

Bangladesh is highly vulnerable to climatic events; floods and droughts are frequent and damaging (Karim, 1996; Huq et. al., 1996). On one hand, droughts of different intensities occur, especially in the drier regions of the country, due to the uncertainty and uneven temporal and spatial distribution of rainfall, and on the other, floods occur due to local rainfall of high intensity and overflow of rivers (Karim et al., 1994). The crop most affected by floods and droughts are rice of different types. Rice alone contributes 94.92 per cent of the total cereal production followed by wheat (5.02 per cent) and the rest (0.05 per cent) by other crops (computed from BBS, 1997). Table-1 gives the summary of major cereals grown in Bangladesh.

TABLE 1. Crop statistics of major cereals for the fiscal year 1994-95

Crop

HYVAus HYVAman HYV Bora Other Rice Rice Total Wheat Major Cereal Total

Area (thousand ha)

415 2,146 2,409 4,951 9,921

592 10,513

Average yield (tonnes ha.1)

2.42 2.96 3.56 1.63 2.29 1.85

Current production (thousand tonnes)

702 4,484 6,200 5,447

16,833 890

17,723 Note: Average yields are national averages. Rice average yields are expressed as rough rice.

Floods, especially the untimely ones, offer excessive moisture at the root zones. As a result, the growth of the plant is hindered, resulting in an overall decline in production of the crop. It is often found that transplanted HYV A man paddy does not grow well under submerged conditions of over 90 em water depth. Such a relationship with water depth (or moisture availability), however, is variety specific. At present about one Mha of cropland is highly and nearly five Mha is moderately flood prone. More than 2.6 Mha is affected by the normal flooding. Usually, the flooding depth varies from 30 to 250 em. The extent of the unprecedented flood of 1998 inundated two-thirds (8.4 Mha) of the country. The estimated loss offoodgrain well exceeded 3.5 Mt.

Natural events such as flash-floods often mauls standing crop, especially maximum impact is observed in case of Boro paddy at the ripening stage at the haor (wet basin) areas of Bangladesh. The effect often lasts for less than 24 hours, but it may have devastating effect on the production of the crop.

Drought (phenological) refers to a condition when the moisture availability at the root zone is less than adequate. It is often observed when there is extremely high rate of


evapotranspiration or high index of aridity. As the evapotranspiration of soil becomes high, it forces the soil to be unsuitable for plant growth. This is how Aman cultivation suffers from periodic drought conditions. Similar conditions are often observed in early pre-Kharif months, affecting Bora and wheat cultivation in the northeast and centraleast regions of the country. Drought-related vulnerability may be counteracted either by supplementary irrigation for the Kharif or extensive irrigation for the Rabi and preKharif crops. Drought normally affects about 2.3 Mha of cropland during the period from April to September (Kharif season) and 1.2 Mha in the dry season (October to March). Drought during Kharif severely affects the transplanted Aman rice, reducing the annual production by about 1.5 Mt of rice. On the other hand, dry season drought affects the production of wheat, potato, mustard and A us paddy (Karim et. a!., 1990).

In the winter months the coastal croplands suffer due to salinity re~ated problems. In absence of appreciable rainfall the soil in the coastal areas starts to desiccate, and because of capillary actions salt comes up at the surface of the soil and accumulates at the root zones. Salinity problem is often intensified when high spring tides inundate low-lying coastal areas, especially when they are associated with cyclonic storm surges. Many of the crop varieties, especially those of foodgrain varieties, are not salinity tolerant. As a result, a large area in the coastal districts is virtually unsuitable for a number of crops, while the production of a few other crops is lesser under saline conditions. Since salinity intrusion restricts cultivation of Bora and wheat, the potential impact can not be ascertained. However, the varieties that are grown with the given conditions, about 0.13 Mt foodgrain is lost annually due to adverse impact of soil salinity.

Low-flow conditions in the rivers are often observed in the winter months (lean period) when surface water irrigation becomes severely constrained. Under such conditions, the farmers usually take necessary actions to ensure irrigation by exploiting groundwater resources. Low-flow conditions do not cause direct vulnerability to crop production, but cause economic hardship to the poor farmers. The situation is observed in the upland areas in the northwest (Barind Tract) and in the lower Ganges floodplains.

In about 8.0 Mha ofland, soil organic matter content is below the critical level (<1.7%) and 4.5 Mha is marginally above this level. It is known that decomposition of organic matter in soils is positively correlated with temperature and moisture (Walker and Steffen, 1997). The tropical weather in Bangladesh often influences depletion of organic matter content of the soil. In the past, nutrient replenishment in soils used to take place during perennial inundation. With increasing deforestation in the Himalayas, instead of loads of sediments enriched with nutrients and weathered material, more coarse silts come in and settle on the topsoils of inundated lands. This also contributes to gradual depletion of organic matter content from the topsoil.


3. Climate Change Induced Vulnerability to Crop Production

The relationship between climate change and agriculture is a vital issue. Since the world's population is increasing rapidly, more pressure is put on the existing food production resources to meet the ever increasing demand. Both land use pattern and the productivity of crops are likely to change under global warming (Solomon and Leemans, 1990). It is important to examine how climate change affects the foodgrain production of Bangladesh.

Agricultural activities are already highly susceptible to the elements of nature or biophysical systems of the country. A favourable weather helps the farmers to have a good harvest while a bad patch of local weather spoils the expected harvest. Soil, the most important natural resource for agricultural activities, is highly responsive to physical systems. A rise in surface temperature may cause higher rates of decomposition of soil organic matter, the latter having significant effect on crop yield. It is often observed that, a little rainfall in early February helps the standing Boro cultivation to a significant extent while higher local rainfall may lead to severe floods in late August, resulting into significant decline in area suitable for Aman cultivation. Similarly, both temperature and evapotranspiration have significant impacts on crop production in Bangladesh.

Unfortunately all such effects will aggravate under climate change and foodgrain production would be lot more difficult than it is today. Each of the problems described above would be detrimental to foodgrain production. Unless these are analysed in an integrated manner, it would be difficult to assess the overall impact of climate change on food production. This study aims at examining the impact of climate change induced parameters that have significant effects on bio-physiological aspects of crop production. A simulation modelling exercise has been carried out to assess the response of rice and wheat crops to temperature, moisture availability, C02 fertilisation with increasing concentration of C02 in the atmosphere etc.

3.1 EFFECT ON AGGREGATED PRODUCTION OF FOODGRAIN

The staple food for about 122 million people of the country is rice and wheat. About half of the total foodgrain has been contributed by the high yielding varieties (HYV) of rice and wheat. Moreover, these would be more susceptible to changes in climate system. Therefore, this study considers the impacts of climate change only on HYV rice and wheat. Six locations representing the drier (Jessore and Rajshahi), wetter (Sylhet and Mymensingh) and coastal regions (Chittagong and Barisal) of the country were chosen for this study (Figure-1).

3.1.1. Climate Models The baseline and the future climate change scenarios were constructed using two general circulation (climate change) models: the Canadian Climate Change model


FIGURE l. Administrative map of Bangladesh. Study regions selected are marked with a dot

N

w.<f' BAY OF BENGAL

50000 0 50000 100000 Meters ----~


(CCCM) and the Geophysical Fluid Dynamic Laboratory model GFDL. The outputs were used as inputs for the crop model experiments. (For a more detailed understanding about the function of the general circulation models, please see Ahmed and Alam, 1998.

3.l.Z. Crop Models The simulation runs for rice and wheat were made by using CERES-Rice and CERESWheat models of DSSAT version 3.0, respectively (Tsuji et a!., 1994). Eighteen experiments (3 crops * 6 locations) for rice crop and three experiments for wheat ( 1 crop * 3 locations) were considered. " Each experiment has been composed of 11 treatments.

Simulation study was conducted for three HYV rice crops, grown during three different growing seasons a) Aus (March-August), b) Aman (July-November) and c) Boro (December-May). Table-1 gives the current statistics of these crops. The selected varieties were BR14, BRll, and BR3 for Aus, Aman and Boro, respectively. In the simulation experiments Aus rice was planted on 01 April, Aman rice on 15 July and in case of Boro rice the planting date was 01 February. The variety chosen for wheat was 'Akbar,' that was planted on 5 November in Jessore and Rajshahi and on 15 November in Mymensingh. Two planting dates for wheat were used because the median planting dates varied with locations.

Compared to baseline yields of rice crops in all locations and all growing seasons, the yield reductions were noted for both CCCM and GFDL scenarios. Computing the aggregated production of rice and wheat, using the current baseline model outputs of the earlier study (Karim eta!., 1996) the following results were obtained. Table-Z gives the summary of aggregated production of rice and wheat. Production of HYV rice and wheat for the entire country were aggregated crop-wise and season-wise. The observations are discussed in the following sections.

3.1.3. HYV Aus Rice The average aggregated production of HYV Aus rice was 0.70 Mt during 1994-95. Under both CCCM and GFDL scenarios the production was reduced by Z7 per cent. When the C02 concentration levels in the atmosphere increased to 580 and 660 ppmv without any temperature rise, the production increased by 31 and 40 per cent, respectively.

Rise of temperature by zoe at 330 ppmv, C02 resulted in 19 per cent reduction in aggregated production level. While, zoe temperature rise at 580 and 660 ppmv C02

increased the aggregated production by 13 and ZZ per cent, respectively. Further increase in temperature to 4°C at 330 and 580 ppmv C02 levels reduced the production by 38 and 6 per cent, respectively, but increased the production by only 4 per cent at 660 ppmv C02 level.


3.1.4. HYV Aman Rice The aggregated production of HYV Aman rice for the year 1994-95 was 4.48 Mt. Simulation results show that under the CCCM scenario the production was lowered by 7 per cent. Under the GFDL scenario it was reduced by 13 per cent. At 330 ppmv C02

level the production reductions were 13 and Z5 per cent for zoe and 4°C temperature rise, respectively. At the 580 and 660 ppmv C02 levels, the effect of temperature was also detrimental but the productions, in each case, were higher than the baseline.

TABLE2. Rice and wheat production under different climate change scenarios

Simulation HYV Aus HYVAman HYV Boro Wheat ('000' Percent ('000' Percent ('000' Percent ('000' Percent tonnes) change tonnes) change tonnes) change tonnes) change

Baseline (I 994-95) 702 0 4,484 0 6,200 0 890 0 CCCM 512 -27 4,170 -7 6,014 -3 712 -20 GFDL 512 -27 3,901 -13 5,766 -7 347 -61 330 ppmv C02 +2°C 569 -19 3,901 -13 5,952 -4 561 -37 330 ppmv C02 +4°C 435 -38 3,363 -25 5,766 -7 285 -68 580 ppmv C02 +0°C 920 31 5,605 25 7,626 23 1,228 38 580 ppmv C02 +2°C 793 13 4,977 11 7,440 20 881 -1 580 ppmv C02 +4°C 660 -6 4,529 7,192 16 534 -40 660 ppmv C02 +0°C 983 40 5,964 33 8,060 30 1,317 48 660 ppmv C02 +2°C 856 22 5,336 19 7,874 27 970 9 660 ppmv C02 +4 oc 730 4 4,888 9 7,626 23 614 -31

3.1.5. HYV Bora Rice The baseline production of HYV Bora rice for the year 1994-95 was 6.ZO Mt. It was noted that the production under CCCM and GFDL climate scenarios decreased by 3 and 7 per cent, respectively. The production decreases were similar for zoe ( 4 per cent) and 4°C (7 per cent) temperature rise to those noted for CCCM and GFDL scenarios, respectively. The increased production over the baseline varied between 16 and 30 per cent for rise in temperature and C02 levels. In general, though the production increased, 4°C temperature rise was more detrimental than zoe rise irrespective of C02 levels.

3.1.6. Wheat The baseline production of wheat for the year 1994-95 was 0.89 Mt. Under CCCM and GFDL scenarios the production was reduced by ZO and 61 per cent, respectively. Temperature rise of zoe and 4°C caused production loss of 37 and 68 per cent at 330 ppmv C02 levels, respectively. For zoe and 4°C rise at 580 ppmv C02 level, the production loss was 1 and 40 per cent, and for zoe rise at 660 ppmv C02 level the production increased by 9 per cent, but for 4°C rise the production was reduced by 31 per cent. In general, higher level of C02 at baseline temperature increased the production by percentages ranging from 38 to 48.


3.2 EFFECT OF CLIMATE CHANGE ON CROP GROWING SEASON

In general, with an increase in temperature the crop growing season decreased by 2 to 12 days as compared to the baseline temperature. Under CCCM and GFDL the reductions were 7 to 10 days, respectively. This clearly suggest that a delay in Aman transplantation caused by climate induced enhanced flooding might not allow the farmers to grow the crop. Reduction in growing period for the common crops would restrict the choice of the farmers and in particular, negate the possible increase in crop production due to C02 fertilisation. Season length under CCCM appeared to be shorter compared to that under GFDL.

3.3. MOISTURE STRESS SCENARIO

During the past three decades, irrigated agriculture has played a major role in total rice production. In the fiscal year 1994-95, the total irrigated area was 3.29 Mha among which 2.77, 0.36, and 0.15 Mha were irrigated by modern, traditional and canal methods, respectively. At present, about 26.6 per cent of the total rice grown in the country is irrigated. Boro rice is primarily an irrigated crop, occupying about 71.3 per cent of the total irrigated area (BBS, 1997). The growth of irrigation in the long-run would be retarded because of low-flow conditions of the river syste~ during the drier months. The potential for groundwater is also likely to diminish because of its extraction for nonagricultural purposes. Furthermore, the connection between arsenic pollution of ground water and over-exploitation of it has become a well established fact and thereby it would not be possible to maintain growth of irrigation with groundwater resources.

It was found that the impact of moisture stress on Boro rice was significant under baseline climate. The yield reductions varied with locations. At moderate moisture stress i.e., up to 30 per cent moisture stress, yield reduction was low, ranging between 1 to 4 per cent. However, at higher level of moisture stress (at 60 per cent), yield reduction would range between 10 to 33 per cent. Under CCCM scenario yield reductions varied between 3 and 7 per cent at no moisture stress, 18 to 35 per cent at moderate moisture stress and 58 and 64 per cent at high moisture stress. Similarly, under GFDL scenario, the yield reductions varied between 3 and 9 per cent, 16 and 33 per cent; and 55 and 62 per cent at no, moderate and high moisture stress, respectively. The results are presented in Table-3.

Compared to the baseline yield, doubling of C02 level increased yield by 16 to 26 per cent at no moisture stress. The benefits of C02 fertilisation diminish rapidly along with increasing moisture stress. Temperature rise causes a more dramatic result - a further reduction of possible yield. In general, at 660 ppmv C02 level and a 4°C temperature rise under no moisture stress cause up to 20 per cent increase in yield. But an increase in moisture stress up to 60 per cent reduced the yield in that tune of 19 to 32 per cent as compared those obtained for baseline scenario.


TABLE 3. Percent change in Bora yields under different climate scenarios and irrigation levels

Simulation Jessore Rajshahi Chittagong

330 C02+No Moisture Stress 0 0 0

CCCM +No Moisture Stress -9 -3 -7

CCCM +30% Moisture Stress -35 -34 -18

CCCM +60% Moisture Stress -58 -63 -64

GFDL+No Moisture Stress -5 -3 -9

GFDL+30% Moisture Stress -33 -25 -16

GFDL+60% Moisture Stress -58 -55 -62

330 C02+30% Moisture Stress -2 -1 -4

330 C02+60% Moisture Stress -29 -33 -10

660 C02+No Moisture Stress 22 26 16

660 C02+30% Moisture Stress 17 16 12

660 C02+60% Moisture Stress 10 3 15

660 C02+ 4°C +No Moisture Stress 6 20 8

660 C02+4°C +30% Moisture Stress -2 6 10

660 C02+4°C +60% Moisture Stress -32 -32 -19

The results obtained may be compared to results from other modelling exercises. Mahmood and Hayes (1995) assessed the impact of climate change on Boro rice in Bangladesh using the YIELD model. They found that per 1 oc increase in air temperature, the yield was reduced by 4.6 per cent. They also reported that each 10 per cent increase in solar radiation resulted in a 6.5 per cent increase in Boro rice yield. Shin and Lee (1995) found that increased C02 concentration would increase the yield. The average per cent increase were 18.3 and 28.3 for the 1.5xC02 and 2xC02 scenarios, respectively. Fertilisation effect of doubling of C02 concentration on Aus rice was 40 per cent, 33 per cent on Aman rice and 30 per cent on Boro rice, while it was 48 per cent in case of wheat. But according to Walker and Steffen ( 1997) the positive effect on yield for 2xC02 fertilisation would be much lower (5-7 per cent increase). If this is the case, for a 2°C rise in temperature much lower values would be obtained than those given in Table-2. In case of 4°C rise, especially for Aus and Aman rice corps, 2xC02

fertilisation would not be able to offset the temperature rise effect. The situation for wheat will be more damaging.

4. Implication of Climate Change

In rural Bangladesh, inundation to a lesser degree has always been considered a boon to agricultural production and people welcome such physical effects. On the other hand, a prolonged flood with high degree of submergence, similar to that occurred in 1998, has been regarded as a disaster for agriculture. In two severe flood years of 1974 and 1987, the shortfalls in production were about 0.8 and 1.0 Mt, respectively. Severe floods, however, do not appear every year. In general, perennial floods bring silt and nutrients


associated with it, which is good for agriculture. With a receding flood, the farmers always fmd ways to readjust with the cropping calendar and grow alternative crops. Flash-flood occurs only in some designated areas. Recently crop loss due to flash-flood has been successfully minimised by introducing the submergible embankments in the susceptible areas. Therefore, flood related vulnerability is not acute in the country.

On the other hand, both drought and salinity intrusion have considerably higher impacts on crop production. Both are annual events, often observed with the onset of dry months. Both the effects diminish suitability of a number of seasonal crops that are usually preferred by the farmers. Under-a severe climate change scenario the potential shortfall in rice production could exceed 30 per cent from the trend, while that for wheat and potato could be as high as 50 and 70 per cent, respectively (Karim, 1996). Under a moderate climate change scenario the croploss due to salinity intrusion could be about 0.2 Mt, which could be increased up to 0.56 Mt under a severe climate change scenario (Habibullah et a!., 1998). Considering the loss of production due to such effects, one may fmd these to have relatively higher intensity than the floods. However, the loss incurred in other sectors could be much higher in case of floods. The effect of low-flow on agricultural vulnerability is considered to be much less intense compared to other effects.

Higher levels of temperature and precipitation would aggravate declining condition of the soils. The organic matter content of the topsoil in majority of the areas has already declined below a critical level. The moderately affected areas would also suffer due to impact of climate change. It is likely that a significant part of the moderately affected soils would become more vulnerable due to further decline in organic matter content of the topsoils (Figure-2). It would certainly have adverse impact on foodgrain production.

Since climate change would cause significant changes in all these physical effects, it is obvious that the overall vulnerability of crop agriculture will be much higher compared to the modelling results. However, the higher concentrations of C02 in the atmosphere would also have some positive effects on the production, as revealed by the modelling exercise. Thereby, some of the adverse effects would be minimised due to C02

fertilisation.

During the period 1961 to 1991 four population censuses were conducted. According to these census results, the population has almost doubled in "less than 30 years since 1961, and is likely to be double again in another 35 years. Currently, the estimated population stands at over 125 million and by the year 2030 it is projected to be 191.1 million (World Bank, 1993). According to the projection made by BARC (1995) the requirement offoodgrain in the country at 2 per cent annual growth rate will be 25.2 Mt in the year 2000 and 42.8 Mt in the year 2030. Therefore, to become self-sufficient in foodgrain production in year 2000 and year 2030, additional 6.2 and 23.8 Mt, respectively would be required. But the increased vulnerability to crop production due to changes in climate system would not allow the farmers of the country to provide food


security for the millions of its countrymen. Unless appropriate anticipatory adaptation measures are considered now, foodgrain self-sufficiency would remain a distant dream for the country.

FIGURE 2. Status of organic mater content in the soils of Bangladesh

LEGEND

Very Low (<1% Organic Matter) Low ( 1-1.7% Organic Matter) Medium (>1 .7-3.5% Organic Matter) High (>3.5% Organic Matter) Reserve Forest

N

$• I·~

Sundarbans UrbanNVater bodies

w~· '-- e \,_r.~··y

s


5. Management Options for Adaptation to Reduce Vulnerability

Using the existing technological bases, the production of cereals, pulses, and oilseeds can be greatly increased by the year 2000 to 2030 from the present potential biophysical resources. The existing technologies would not be adequate to address the problem. However, efforts are being made to increase the yield frontier of rice. Pingali et al., (1997) stated "Recent advances in shifting the yield frontier for rice indicate that the prospects for sustaining productivity growth in the intensively cultivated irrigated lowlands of Asia are high. In the short to medium term, yield growth would come from the adoption of hybrid rice and in the longer run through the use of 'super rice' and second-generation hybrids between modem Indica varieties and the new plant type". In developing these cultivars, one should have the perspective of climate change and secondary problems such as - pest attacks, floods and droughts of higher intensities etc. associated with this change. These cultivars should have higher resistance to pests and diseases, tolerance to higher temperature, submergence, salinity and drought.

Matthews et al. (1995) reported that high temperature tolerant varieties are capable of counteracting the detrimental effect of a temperature rise in currently high-temperature environments. To avoid spikelet sterility, management practices may be restructured and shorter duration varieties may be considered which would allow the crop to grow and develop within the favourable part of the season.

To tackle the problem of higher rate of evapotranspiration due to increase of leaf area index of plants (Lal et al., 1996) and water scarcity, effort should be made to develop cultivars with lower transpiration ratio values. From available literature, it is known that for C3 plants, about 500 molecules of water are lost for every molecule of C02

fixed by photosynthesis, giving a transpiration ratio of 500. For C4 plants, about 250 molecules of water are lost for every molecule of C02 fixed by photosynthesis, giving a transpiration ratio of 250. Desert adapted plants with CAM (Crassulacean acid metabolism) photosynthesis, in which C02 is initially fixed into four-carbon organic acid at night, have even lower transpiration ratios; values of about 50 are not unusual (Taiz and Zeiger, 1991). Field trials of crop cultivars thus appear to be inevitable step for examining alternative crops suitable for local adoption.

6. Conclusions

The impact of climate change on foodgrain production may not always be a problem. The crop cultivars available are capable to produce higher than the current levels under situations of higher temperatures associated with the speculated C02 rise. If the C02

level increases without increasing the temperature, especially in the tropics, it would have been a blessing. Doubling of C02 , as estimated by different GCM, indicates temperature rise in the tune of>1 to 2.6°C (Ahmed and Alam, 1998). The rice varieties now in use may not be able to tolerate temperature rise due to greenhouse effect and sustain current level of yield.


There is no such system, which is perpetual. If more output is expected from a system, more input is required. One may not have to pay for more C02, or solar radiation for increasing agricultural production but for assimilation of these, more water, nitrogen etc. are required. Moreover, the standing crop failure due to prolonged submergence, flash floods and salinity intrusion have to be tackled by devising anticipatory adaptation techniques. Long-term investments for the development of infrastructure and research may play a vital role in adapting to adversities. Increasing the production of crops, especially in the under-developed and developing countries, will not be an easy task.

However, In order to meet the demand of foodgrain beyond 2010, there is an urgent need to develop rice cultivars having high photosynthetic efficiency, that are capable of yielding more than 8.0 t ha-1 and suitable for 4.5 Mha of highland in the country. For the 2.6 Mha ofland which is inundated under a water-column of more than 180 em, it is necessary to develop flood tolerant modem rice cultivars with short duration for growth. For the drought affected land wheat cultivars having yield greater than 5.0 t ha·1

at the farm level should also be developed. Wider germplasm bases along with modem management practices should be made available to 2.85 Mha of coastal saline and tidal land, and drought prone areas of the country. Management packages should be made available to the farmers with adequate extension services. Successful adaptation of the management packages, as envisaged, would enable the farmers to grow an additional amount of about 40 to 50 Mt cereals annually. Bangladesh must have wider choices of both germplasm and management practices for cereals, oilseeds, pulses, vegetables and fruits. Research efforts should be geared up for varietal break-through in genetic engineering.

References

Ahmed, A.U. and Alam, M., 1998. Development of Climate Scenarios with.General Circulation Models, In Vulnerability and Adaptation to Climate Change for Bangladesh. S. Huq, Z. Karim, M. Asaduzzaman and F. Mahtab (Eds.), Kluwer Academic Publishers, Dordrecht, The Netherlands. pp. 13-20.

BARC, 1995. Strategic Plan for NARS to the Year 2010 and Beyond. Bangladesh Agricultural Research Council, Dhaka.

BBS (Bangladesh Bureau of Statistics), 1997. Yearbook of Agricultural Statistics of Bangladesh 1996. Statistics Division. Ministry of Planning. Government of the People's Republic of Bangladesh.

Habibullah, M., Ahmed, A.U., and Karim, Z., 1998. Assessment of Foodgrain Production Loss Due to Climate Change Induced Enhanced Soil Salinity. In Vulnerability and Adaptation to Climate Change for Bangladesh. S. Huq, Z. Karim, M. Asaduzzaman and F. Mahtab (Eds.), Kluwer Academic Publishers, Dordrecht, The Netherlands. pp. 55-70.

Huq, S., Ahmed, A.U. and Koudstaal, R., 1996.Vulnerability of Bangladesh to Climate Change and Sea Level Rise. In Climate Change and World Food Security, T.E. Downing (Ed.), NATO ASI Series, 137. Springer-Verlag, Berlin, Hiedelberg, 1996. pp. 347-379.


IBSNAT, 1989. Decision Support System for Agrotechnology Transfer Version 2.1 (DSSAT V2.1). Department of Agronomy and Soil Science, College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu.

Karim, Z., 1996. Agricultural Vulnerability and Poverty Alleviation in Bangladesh. In Climate Change and World Food Security, T.E. Downing (Ed.), NATO ASI Series, 137. Springer-Verlag, Berlin, Hiedelberg, 1996. pp. 307-346.

Karim, z., Ibrahim, A.M., Iqbal, A. and Ahmed, M., 1990. Drought in Bangladesh Agriculture and Irrigation Schedules for Major Crops. Bangladesh Agricultural Research Council, Soils Publication No: 34, pp. 11.

Karim, Z., Hussain, S.G. and Ahmed, M., 1996. Assessing Impacts of Climatic Variations on Foodgrains Production in Bangladesh. Journal of Water, Air, and Soil Pollution, 92: 53-62.

La!, M., Singh, K.K., Rathore, L.S., Srinivasan, G. and Saseendran, S.A., 1996. Vulnerability of Rice and Wheat Yields in Northwest India to Future Changes in Climate. Centre for Atmospheric Sciences, Indian Institute of Technology, Technical Report No: A/TR/1-96 (August 1996), New Delhi, India, pp. 29.

Mahmood, R. and Hayes, J.T., 1995. A Model-Based Assessment oflmpacts of Climate Change on Bora Rice Yield in Bangladesh. Physical Geography 1995, 16:463-496.

Matthews, R.B., Rorie, T., Kropff, M.J, Bachelet, D., Centeno, H.G., Shin, J.C., Mohandass, S., Singh, S., Defeng, Z. and Lee, M.H., 1995. A Regional Evaluation of the Effect of Future Climate Change on Rice Production in Asia. In Modelling the Impact of Climate Change on Rice Production in Asia. R.B. Matthews, M.J. Kropff, D. Bachelet and H.H. Van Laar, (Eds.). CAB International, Wallingford, Oxon, OX10 SDE, UK. pp. 95-139.

Pingali, P.L., Hossain, M. and Gerpacio, R.V., 1997. Asian Rice Bowls: The Returning Crisis? CAB International in association with IRRI.

Reilly, J. (Ed.), 1996. Agriculture in a Changing Climate: Impacts and Adaptation. In Climate Change 1995, Impacts, Adaptations and Mitigation of Climate Change: Scientific-Technical Analysis; R.T. Watson, M.C. Zinyowera and R.H. Moss (Eds.), pp. 427-467.

Rosenzweig, C. and Iglesias, A., 1994. Implications of Climate Change for International Agriculture: Crop Modelling Study. EPA 230-B-94-003, U.S. Environmental Protection Agency, Washington D.C., 312 pp.

Rosenzweig, C and Parry, M.L.,1994. Potential Impact of Climate Change on World Food Supply, Nature, 367, 133-138

Shin, J.C. and Lee, M.H., 1995. Rice Production in South Korea under Current and Future Climates. In Modelling the Impact of Climate Change on Rice Production in Asia, R.B. Matthews, M.J. Kropff, D. Bachelet, and H.H. VanLaar (Eds.):CAB International, Wallingford, Oxon, OX10 SDE, UK. pp. 199-215.

Solomon, A.M. and Leemans, R., 1990. Climate change and landscape ecological response: Issues and analysis. In Landscape Ecological Impact of Climate Change; M.M. Boer and R.S. de Groot (Eds. ). lOS Press, Amsterdam, pp. 293-316.

Taiz, L. and Zeiger, E., 1991. Plant Physiology. The Benjamin/Cummings Publishing Co. Inc., 390 Bridge Parkway, Redwood City, California 94065.


Tsuji, G.Y., G. Uehara and S. Balas (Eds.), 1994. DSSATversion 3.0. IBSNAT. Department of Agronomy and Soils, University of Hawaii, Honolulu, Hawaii.

Walker, B., and Steffen, W., 1997. An overview of the implications of global change for natural and managed terrestrial ecosystems. Conservation Ecology [online] 1(2): 2. Available from the Internet. URL: http://www.consecol.org/vollliss2/art2

World Bank, 1993. World Population Projection 1992-93.

ASSESSMENT OF FOODGRAIN PRODUCTION LOSS DUE TO CLIMATE INDUCED ENHANCED SOIL SALINITY

MOHAMMAD HABIBULLAH Independent Consultant


ZAHURUL KARIM Executive Chairman Bangladesh Agriculture Research Council (BARC)

ABSTRACT

The loss of foodgrain production due to soil salinity intrusion in the coastal districts was estimated under climate change scenarios. A computer model was developed that provided with a genesis of soil salinity build-up in the relatively drier months of the crop calendar. The time-series soil salinity database was compared with the field-level observations and the model was validated. It was found that the soil salinity generally increases rapidly in the winter months and reaches maximum values in April.

The time-series database was then correlated with the time specific events in the crop calendar for two crops, Aman and Aus rice, to estimate the damage in production due to adverse effects of salinity. It was found that the impacts of soil salinity would be manifold under the climate change scenarios. It was also found that the estimated crop loss under the severe climate change scenario would be the maximum. Furthermore, more areas would become severely affected by soil salinity and thereby the affected lands would become unsuitable for a number of crops. As a result, the food security of the country would be threatened under climate change.

The modelling was extended to examine crop loss considering adaptation in conjunction with the climate change scenarios. The results show that substantial improvement might be achieved by adapting to increased soil salinity, yet the projected loss would be significant.

55

56 M. HABIBULLAH, A.U. AHMED and Z. KARIM

1. Introduction

Over thirty percent of the net available cultivable lands of Bangladesh are located in the coastal areas. But it has been observed that all the coastal cultivable lands are not being utilised for crop production, mostly due to soil salinity. Increased soil salinity, in one hand, limits growth of standing crops and affects overall crop production and in the other hand, make the affected soil unsuitable for many potential crops. Soil salinity has been considered as a major constraint to foodgrain production in coastal areas of the country.

It is believed that the impact of cliinate change on physical systems in combination with the effect of sea level rise would cause a net increase in salinity in the already affected soils in the coastal regions. A GCM modelling approach has indicated that, under changed climate conditions the index of aridity will increase during winter (Ahmed et al., 1996). As a result, an increased rate of desiccation in topsoil leading to higher rates of capillary action would be observed. Hence the salinity problem would be accentuated by the impacts of climate change and sea level rise. The extent of increase in soil salinity in a particular area within the coastal zone would determine the extent of crop loss in the affected areas.

1.1 THE SOIL SALINIZATION PROCESS: AN OVERVIEW

An estimated 1.27 to 1.67 billion tonnes of sediments are carried annually by the river systems of the Ganges-Brahmaputra-Meghna basin (MPO, 1986; Milliman and Meade, 1983). Before being deposited near the sea mouth, the freshly available alluvium from upstream comes in contact with seawater and becomes salty. Thereafter, it becomes more saline by interacting with the seawater that comes along the high tides and through creeks. More salt deposition occurs when capillary action takes place in the sub-surface and topsoil zones, compounded with high evapotranspiration during winter. However, the severity decreases during the onset of monsoon due to the fact that rainwater dilutes the salinity.

Karim et al. (1990) reported that, the soil salinity starts to increase from August and continue to increase until late April when the first rainfall leaches the salt and dilutes the topsoil. The general pattern of soil salinity build-up has been observed in about 0.833 million hectares of the arable lands in 64 coastal Thanas 1 of thirteen Districts. A database was created by compiling information on soil salinity from more than 1,100 pointsources/stations. The maximum values of soil salinity in April for all the stations under each Thana were averaged. The average values of maximum soil salinity of all the Thanas were categorised in five classes. Based on the salinity classes a database was created and the latter was presented in the form of a map showing the most and the least salinity affected Thanas in the coastal areas of Bangladesh (Karim et al., 1990).

1 Thana is a small administrative unit, previously known as Upazila, may be considered as a sub-district.

CLIMATE INDUCED ENHANCED SOIL SALINITY 57

Although such a database provided valuable information regarding maximum salinity in the affected areas, it could not, however, give adequate information regarding the extent of adverse impacts on crop production, especially on food grain production. To establish a relationship between the extent of soil salinity with the crop response functions one requires a time series database on soil salinity, not a database showing only the maximum salinity at a particular time of the year. To assess the general adverse effects of salinity intrusion on foodgrain production in the coastal areas it was deemed necessary to analyse the gradual build-up of soil salinity in the affected areas. In a second step, however, the change in salinity build-up under the different climate change scenarios was analysed and the loss in crop production was estimated. Finally, the assessment was extended to see what would be the overall adverse impact of salinity intrusion if adequate adaptation measures are considered to offset the estimated crop loss.

2. Approach and Methodology

The database for soil salinity under different salinity classes at their maximum values was obtained from secondary sources (Karim et al., 1990). The salinity classes used for categorising soil salinity are presented in Table-1.

TABLE 1. Soil salinity classification on the basis of electrical conductivity

Salinity Class Notation EC Plant growth condition (in dS m·1)

Non-saline so <2 Salinity effects mostly negligible Slightly saline Sl 2 to 4 Yields of very sensitive crop may be restricted Moderately saline S2 4 to 8 Yields of many crops are restricted Saline S3 8 to 16 Only tolerant crops yield satisfactorily Highly saline S4 > 16 Only very tolerant crops yield satisfactorily

Note: EC refers to electric conductivity of saturated aqueous extracts of topsoils Source: Karim et a/., 1990

The monthly rate of change of soil salinity, starting from August to April, was analysed from the point-source data and a model was developed in order to defme salinity regimes at different times for all the 64 Thanas. The model was then validated with field level actual data of 124 stations located in the coastal Thanas mentioned above. A time-series data on soil salinity for the baseyear (1990) was thus obtained.

In the next step the model was extended to analyse soil salinity build-up of the same 64 Thanas under two climate change scenarios: one for a moderate change (CCSl) and the other for a severe change (CCS2). The climate change scenarios are similar to those presented in Ahmed and Alam, 1998. The severe climate change scenario (CCS2) considered higher level of temperature rise with higher level of desiccation in winter months resulting into higher level of salinity intrusion in the coastal lands. The moderate climate change scenario (CCSl), however, considered similar changes to a relatively higher extent compared to those under the baseline scenario, but to a lower extent compared to those under the severe scenario.

58 M. HABffiULLAH, A.U. AHMED and Z. KARIM

Based on expert judgement, it was approximated that the salinity pattern under future climate scenarios would change in the following manner:

i) Under moderate climate change scenario ( CCS 1) 10% of the present non-saline (S0) areas would transform into slightly saline (S1) areas and similarly, 10% of the areas from each lower salinity category would be transformed into areas under the next higher salinity category;

ii) Under the severe climate change scenario (CCS2), 45% of the present non-saline (S0) areas would transform into slightly saline (S1) areas and similarly, 45% of the areas from each lower salinity category would be transformed into areas under the next higher salinity category.

Using the Analytical Hierarchical Principle (Saaty, 1994) each of the salinity category of a Thana was assigned with a value and was multiplied with relative fraction of area under that salinity category for the Thana. Similar exercises were made for each of the salinity categories for each individual Thana. The values thus obtained were added to give a scorecard for that particular Thana. Similar scoring technique was applied to all the 64 Thanas for the two climate change scenarios along with the baseline scenario. The scores of all the Thanas were again categorised into five relative soil salinity classes. This exercise provided a tool that compares the salinity condition of a particular Thana in respect to other Thanas.

This soil salinity data were digitised and the entire database was . transferred into a Geographic Information System (GIS) environment by using a software, namely Arc/Info. The GIS database gave a spatial distribution of the severity of salinity intrusion in the coastal areas for the months between August and April.

The digitised and spatially distributed soil salinity information were plotted using a GIS software (Arc/Info) and soil salinity maps were produced for each of the months under consideration (from August to April). The maps showed how soil salinity of a less-saline Thana increase with time.

The time-series data on areas under a specific soil salinity class was correlated with crop response functions and the sensitivity for rice crops were analysed. Similar approach for the three climate change scenarios gave an estimation of crop loss due to climate change induced salinity impacts.

3. Results

3.1. SOIL SALINITY DEVELOPMENT

The results of computer modelling on monthly averaged soil salinity development under the baseline (no-climate change, CCSO) scenario are shown in Figures-la tole for August,


October, December, February and April, respectively. Areas under each of the salinity class for the baseline scenario (CCSO) are presented in Table-2. It is observed that the soil salinity increases at a considerably faster rate in drier months (i.e., December to April) compared to the rate observed in pre-winter months. Such an observation clearly suggests that the problem concerning soil salinity is related either to low flow conditions in the surface water systems or the desiccation effects of winter climate which is marked with high evapotranspiration. Since most of the coastal areas in the south-west and southcentral regions, with an exception of the Sundarbans, are embanked, low flow does not have profound effect on the salinity build-up on soils. Desiccation through high evapotranspiration along with upward movement of saline groundwater through capillary rise is mainly responsible for salinity intrusion in the soils of the coastal areas. From the above observation one may expect that effects of climate change would accentuate the salinity problem, as reported by Ahmed et al. (1996).

As described earlier, similar treatments and modelling exercises presented similar trends of salinity build-up under the two future climate change scenarios (CCSs). For comparison, the severity of salinity intrusion for the three CCS are presented in two set of figures: Figure-2 represents salinity affected areas for December under the three CCS, respectively, while Figure-3 represents salinity affected areas for April under the three CCS, respectively. It may be observed that, under the severe climate change scenario (CCS2), many of the Thanas would become severely affected which were less affected under the other scenarios. In other words, there would be more areas under higher salinity categories as the climate change scenarios would become more severe. Tables-3 and 4 present salinity affected areas under each salinity class for the moderate and severe climate change scenarios, respectively.

FIGURE Ia.. Area affected by soil salinity in the month of August

Thana Boundary

- Coastal Island

SALINITY CLASSES i SO (Non-saline)

:

S l (Slightly saline)

S2 (Moderately saline)

S3 (Saline)

4 (Highly saline)

Km

0 . so 100 ISO


FIGURE I b. Area affected by soil salinity in the month of October

Thana Boundary

- Coastal Island

SALI ITY C ASSES i SO (Non-saline)

S I ( hghtly saline) 2 (Moderately saline) ~~~~;1)')JW

S3 (Saline)

S4 (Highly saline)

Km

so 100

FIGURE lc. Area affected by soil salinity in the month of December

Thana Boundary

- Coastal Island

SALINITY CLASSES I SO (Non-saline)

S I (Slightly saline)


S3 (Saline)

S4 (Highly saline)

Km

so 100

I SO

ISO

CLIMATE INDUCED ENHANCED SOIL SALINITY

FIGURE ld. Area affected by soil salinity in the month of February

Thana Boundary

- Coastal Island

SALINITY CLASSES i SO (Non-saline)

S I (Slightl y sahne)

2 (Moderately saline)

S3 (Saline)

S4 (Htghly saline)

Km

so 100

FIGURE le. Area affected by soil salinity in the month of April .

LEGEND

- · International Bo

- Di trict Boundary

Thana Boundary

- Coastal Island

SAL! lTV CLASSES i SO (Non-saline)

S I ( lightly saline)


S3 (Sahne)

S4 (Highly saline)

Km

0 so 100

ISO

ISO

61

. i ....


3.2 POSSIBLE IMPACT OF SOIL SALINITY ON FOODGRAIN PRODUCTION

At present there is no Boro cultivation in the coastal area. The soil is also unsuitable for cultivation of the other grain- wheaf. Such a limitation is observed due to the fact that, both Boro and wheat are usually cultivated in winter months and salinity reaches its maximum in those months leaving most of the lands unsuitable for rice and/or wheat production. In pre-monsoon and monsoon months, on the other hand, salinity problem is no longer a limiting factor. As a result, it appears to be possible to cultivate A us and A man varieties of rice in those areas between late May and September. In such cases, however, the expected yield would be reduced by certain degrees depending 0n the soil salinity concentration (Karim et al., 1990).

TABLE2. Soil salinity distribution under baseline condition (CCSO)

Month Area under different soil salinity class (in thousand hectares)

so S1 S2 S3 S4 August 287.4 426.4 75.8 41.9 2.0 September 258.6 433.9 93.1 45.9 2.0 October 244.3 426.9 110.4 47.9 4.0 November 215.5 391.7 170.4 45.9 11.0 December 201.2 406.0 162.4 51.9 12.0 January 201.2 384.7 179.8 55.8 12.0 February 172.4 413.5 175.8 57.8 14.0 March 115.0 428.3 210.5 63.8 16.0 April 0.0 287.4 426.4 79.8 39.9

TABLE3. Soil salinity distribution under the moderate climate change scenario (CCS1)

Month Area under different soil salinity class (in thousand hectares)

so Sl S2 S3 S4 August 258.6 412.5 108.7 51.2 2.4 September 232.8 417.8 123.6 56.9 2.4 October 219.8 410.1 138.5 60.3 4.8 November 194.0 374.1 194.7 58.8 11.8 December 181.0 387.0 183.2 67.8 14.4 January 181.0 366.4 198.1 73.6 14.4 February 155.2 392.2 192.4 76.9 16.8 March 103.5 402.7 222.2 85.9 19.2 April 0.0 258.6 412.5 114.4 47.9

The available international literature on impacts of salinity on different crops suggest that, the soil salinity reduces productivity of rice during its germination, vegetative (early) growth and reproductive stages (Bhumbla et al., 1968; Rai, 1977a; Rai, 1977b; Ayers and Westcot, 1976; Das et al., 1971; BRRI, 1983; BARC, 1981-82 and BARC, 1982-83).

2 Wheat is only possible where thermal situation permits and early sowing is possible.

CLIMATE INDUCED ENHANCED SOIL SALINITY

FIGURE 2. Soil salinity distribution for December under the three climate change scenarios

Baseyear LEGEND

CCSl

CCS2

- · International Boundary

- District Boundary

Thana Boundary

- Coastal Island


Sl (Slightly saline)


S3 (Sahne)

S4 (Highly saline)

LEGEND


- District Boundary

Thana Boundary

- Coastal Island


Sl {Shghtly saline)


S3 (Saltne)

S4 (Highly saline)

LEGEND


- District Boundary

- Thana Boundary

- Coastal Island


S l {Slightly saline)

S2 {Moderately saline)

S3 (Saline)

S4 (Highly saline)

63


FIGURE 3. Soil salinity distribution for April under the three climate change scenarios

Baseyear LEGEND

CCSI

CCS2


- District Boundary

Thana Boundary

- Coastal Island


S I (Slightly sahne)


SJ (Sahne)

S4 (Highly saline)

LEGEND


- District Boundary

- Thana Boundary

- Coastal Island


.'

S I (Slightly saline)


SJ (Saline)

S4 (Highly saline)

LEGEND


- District Boundary

- Thana Boundary

- Coastal Island

SALINITY CLASSES I SO (Non-sal ine)

Sl (Slightly saline)


S3 (Saline)

S4 (Highly saline)


Looking at the annual crop calendar in the coastal areas, it is obvious that the germination or early growth stages for all the A man variety would not be affected by salinity, only the effect would be significant at the reproductive stage. On the other hand, for both broadcast and high yielding varieties of A us paddy the effect of soil salinity would be pronounced during both the germination and early vegetative growth stages.

TA,BLE4. Soil salinity distribution under the severe climate change scenario (CCS2)

Month Area under different soil salinity class (in thousand hectares) so Sl S2 S3 S4

August 158.1 363.9 224.0 83.8 3.8 September 142.3 361.5 230.4 95.6 3.8 October 134.4 351.2 236.8 103.6 7.6 November 118.5 312.4 279.6 104.0 19.0 December 110.6 320.3 256.0 123.8 22.7 January 110.6 302.1 262.4 135.6 22.7 February 94.8 317.9 250.6 143.6 26.5 March 63.2 313.1 263.4 163.4 30.3 April 0.0 158.1 363.9 235.8 75.8

The modelling exercise under the present study estimated the loss in foodgrain due to soil salinity impacts under the three climate change scenarios. Tables-5 and 6 provide information on potential loss of production of two types of rice, Aus and Aman, respectively, under different climate change scenarios. Table-7 gives a summary of the results for all the three scenarios.

TABLE 5. Loss of A us production under the three scenarios (without adaptation)

Scenario specification Variety Production loss specification (tonnes)

Baseline (no climate change, CCSO) BAus 39710.3 HYVAus 25907.6 TotalAus 65617.9

Moderate Climate Change Scenario BAus 46139.5 (CCSl) HYVAus 29631.0

Tota!Aus 75770.5 Severe Climate Change Scenario BAus 55579.9 (CCS2) HYVAus 42042.5

Tota!Aus 97622.4

It may be observed from Table-7 that, about 196 thousand metric tonnes of food-grain, almost 66% of which is Aman, is lost annually due to impacts of salinity under the baseline condition (CCSO). The loss in foodgrain production would be about 1.4 and 3.3 times higher under CCSl and CCS2, respectively, in respect to the loss incurred under CCSO. The loss would be much less pronounced in case of Aus production, in comparison


to that for A man production, since only a small fraction of the arable land in the coastal

areas are currently being used for A us crop.

TABLE 6. Loss of A man production under the three scenarios (without adaptation)

Scenario specification

Baseline (no climate change, CCSO)

Moderate Climate Change Scenario (CCSI)

Severe Climate Change Scenario (CCS2)

Variety specification BAman TAman HYVAman Tota1Aman BAman TAman HYV Aman Total Aman BAman TAman HYV Aman Tota!Aman

Production loss (tonnes)

0.0 100270.4 30809.8

130780.2 0.0

150405.6 45764.7

196170.2 0.0

438682.9 122039.1 560722.0

TABLE 7. Total loss in food grain production under the three climate change scenarios

Climate Change

Scenarios Baseline (CCSO) Moderate (CCS I) Severe (CCS2)

Production loss due to soil salinity (in tonnes)

Aus Aman Total grain

65617.9 130780.2 196398.1 75770.5 97622.4

196170.2 560722.0

271940.8 658344.4

FIGURE 4. Total loss in foodgrain production under climate change scenarios

700

600 ~ c:

500 c: B ...,

400 c: "' "' "' 0 300 -:; = "' .., 0 ..J

0

ccnarios


It is expected that, it would be possible by the farmers to implement some adaptation techniques which would reduce the vulnerability due to effects of soil salinity. An attempt was made to estimate the loss under two adaptation scenarios, in addition to the climate change scenarios. It was considered that, under the moderate adaptation (MA) scenario the farmers would be able to adapt moderately with the altered Climate conditions under CCS 1 and they would take the following measures:

i) The land would not be left fallow during dry months and, therefore, would not allow evaporation at higher level from topsoil moisture;

ii) The plants would be placed on raised bed in a double row in combination with irrigation, where the salt would be pushed to the ridge areas of the raised beds.

It was also considered that, by the time the anticipated changes in climatic system would be severe all the technological interventions would be made possible and the farmers would go for each of the alternative measures, whichever might be applicable. In addition to the two adaptation measures mentioned above, the full adaptation (FA) scenario considered the following measures:

i) The uneven micro-relief would be avoided so that salt could not be accumulated in the raised spots;

ii) The turn around time after Aman harvest would be reduced and the land would be subjected to rapid and deep tillage, so that it would break capillary continuity for upward movement of saline groundwater;

iii) Heavy pre-plant irrigation would be implemented so that the salts get leached down below the sowing depth and root-zone of the crop, thus could save it at the germination and early growth stages; and

iv) Fertilisation would be enhanced, depending on the soil quality.

TABLE 8. Loss of A us production under adaptation scenarios

Scenario specification

Moderate Adaptation on Moderate Climate Change (CCSIMA) Full Adaptation on Severe Climate Change (CCS2FA)

Variety specification

BAus HYV Aus Tota!Aus BAus HYV Aus Tota!Aus

Production loss (tonnes) 22280.5 12691.0 34971.6

6374.5 13697.4 20071.9

Implementation of such adaptation measures would necessitate dissemination of the existing knowledge base to the grassroots farmers. Moreover, the farmers have to invest more compared to the present level of investment for crop cultivation. It would also be necessary to increase disbursement of funds for research in order to achieve technological breakthrough regarding saline tolerant C3 and C4 crops.


TABLE 9. Loss of A man production under adaptation scenarios

Scenario specification Variety Production loss specification (tonnes)

Moderate Adaptation on Moderate BAman 0.0 Climate Change TAman 62669.0

HYV Aman 15254.9 (CCSlMA) TotalAman 77923.9 Full Adaptation on Severe Climate BAman 0.0 Change TAman 250675.9

HYVAman 61019.6 (CCS2FA) Total Aman 311695.5

From the modelling exercise it was found that the present level of loss in rice production would be reduced by 42% considering the CCSl scenario coupled with moderate adaptation scenario (CCSlMA). On the other hand, a significant loss in production might be avoided by considering full adaptation on top of severe climate change scenario (CCS2FA), but the overall loss would still be higher compared to that under the baseline scenario. Full adaptation would be able to reduce the potential loss from 659 thousand metric tonnes to 332 thousand metric tonnes under the severe climate change scenario. The results of production loss under the adaptation scenarios are presented in Tables-8, 9 and 10. Figure-4 and Figure-S give graphical presentations of the results.

TABLE 10. Overall foodgrain production loss due to soil salinity with adaptation

Adaptation Scenario Baseline (CCSO) Moderate (CCSIMA) Full (CCS2F A)

Production loss due to soil salinity (in tonnes) Aus A man Total grain loss 65617.9 130780.2 196398.1 34971.6 77923.9 112895.4 20071.9 311695.5 331767.4

FIGURE 5. Production loss under adaptation scenario

"' "' = = ~

"" c 01

"' ::l

" = .: ::l " ...J

Baseline CCSI CCS IMA CCS2 CCS2MA

0)ltions


4. Conclusions

The soil salinity of the coastal areas would be increased due to climate change and

consequential effects. Increased salinity would significantly reduce foodgrain production, especially under the severe climate change scenario. The loss may be minimised by

adapting to some identified measures, yet can not be avoided in totality. Reduction in foodgrain production would put additional threats to the food security of the country.

The present case study is based on a huge database and the future changes in soil salinity patterns are computed based on equations which are validated by using only 10% of the

data. Moreover, the potential loss factors in the two future climate scenarios are based on

expert judgements. Hence, it may not be considered as a complete study, but an indicative

one to predict the loss in foodgrain production in the salinity affected areas. It has limitations regarding the fact that it did not consider other crops that were grown in that

area and also, it did not consider the areas other than the 64 Thanas where soil salinity

might become a potential problem in future. If that would be the case there would be more

loss incurred in foodgrain production. It would require further modelling exercises.

The present study, however, may be used to fmd out the costs for implementation of some

adaptation measures and the potential benefits of such measures. New cropping patterns

are to be developed which would be adapted to reduc·e potential loss in foodgrain

production.

One of the adaptation measure which is implemented in the coastal areas by the farmers

themselves is called dibbling method. The farmers take a spear or a long sharpened stick

to make small holes in the mud and put the seed there for germination. Since the seed is

kept a few inches below the surface it is naturally exposed to lesser concentration of salinity. Thereby, the loss at the germination stage can be reduced. There may be other

local methods which may be researched and then replicated all around the salinity affected areas to reduce the impacts of salinity on foodgrain production.

References

Ahmed, A.U., Huq, S., Karim, Z., Asaduzzaman, M., Rahman, A. A., Alam, M., Ali, M. Y. and

Chowdhury, R.A., 1996. Vulnerability and Adaptation Assessment for Bangladesh. In Vulnerability

and Adaptation to Climate Change, J.B. Smith, S. Huq, S. Lenhart, L.J. Mata, I. Nemesova and S.

Toure (Eds.). Kluwer Academic Publishers, Dordrecht, The Netherlands.

Ahmed, A.U. and Alam, M., 1998. Development of Climate Change Scenarios With General

Circulation Models. In Vulnerability and Adaptation to Climate Change for Bangladesh, S. Huq, Z.

Karim, M. Asaduzzaman and F. Mahtab (Eds.), Kluwer Academic Publishers. pp 13-20.

Ayers, R.S. and Wastcot, D.W., 1976. Water quality for agriculture. Irrigation and Drainage Paper

29, FAO, Rome.


BARC, 1981-82. Second Annual Report. Co-ordinated irrigation and water management project. Bangladesh Agriculture Research Council (BARC) Soils and Irrigation Publication No. 10. Dhaka.

BARC, 1982-83. Third Annual Report. Co-ordinated irrigation and water management project. Bangladesh Agriculture Research Council (BARC) Soils and Irrigation Publication No. 12. Dhaka.

Bhumbla, D.R., Singh, B. and Singh, N.T., 1968. Effect of salt on seed germination. Ind. J. Agron.

13, pp 181-185.

BRRI, 1983. Annual internal review on plant physiology. Bangladesh Rice Research Institute (BRRI), Joydevpur.

Das, S.K. and Mehrotra, C.L., 1971. Salt tolerance of some agricultural crops during early growth

stages. Ind. J Agric. Sci., 41, pp 882-888.

Karim. Z., Hussain, S.G. and Ahmed, M., 1990. Salinity Problems and Crop Intensification in the Coastal Regions of Bangladesh. Bangladesh Agriculture Research Council (BAR C), Dhaka.

Milliman, J.D. and Meade, R.H., 1983. World-wide Delivery of River Sediment to the Oceans. J of Geol., 91, pp 1-21.

MPO, 1986. National Water Plan (Three Volumes). Prepared for the Ministry of irrigation, Water Development and Flood Control, Government of the People's Republic of Bangladesh, UNDP and the World Bank by HARZA Engineering Company International and Sir MacDonald and Partners.

Rai, M., 1977a. Salinity tolerance in Indian mustard and sunflower. Ind. J Agric. Sci., 47, pp 70-73.

Rai, M., 1977b. Varietal resistance to salinity tolerance in maize. Ind. J. Pl. Physiol., 20, ppl00-104.

Saaty, T.L., 1994. Fundamentals of Decision Making and Priority Theory With the Analytical

Hierarchy Process, RWS Publications, Pittsburg.

BEACH EROSION IN THE EASTERN COASTLINE OF BANGLADESH

S.M. RAKIBUL ISLAM Senior Research Officer Bangladesh Centre for Advanced Studies (BCAS)

SALEEMUL HUQ Executive Director Bangladesh Centre for Advanced Studies (BCAS)

ANWAR ALI Chief Scientific Officer Bangladesh Space Research and Remote Sensing Organisation (SPARRSO)

ABSTRACT

Land loss due to beach erosion caused by sea level rise in the eastern coastline of Bangladesh was calculated by using Brunn s formula. Estimation was done for three distinct areas: a) Bakkhali river valley b) Southern beach plain c) Nilla-Teknafplain. In addition Moheskhali channel area was also studied. The slope of this coastline was measured by conducting a survey at 21 different points along north-eastern coast considering coastline profile taken at 9rl angle with respect to sea. These points were interpolated to define the coastline profile: Real world geographical location of each point was captured using Geographical Positioning System (GPS) and subsequently the shoreline profile was coupled with a GIS system.

Bathymetric information was drawn from admiralty charts from which height (depth of water) and width of the continental shelf were determined. Brunn s formula gave the values for shoreline recession for 30 and 75 em sea level rise for the year 2030 and 7 5, respectively.

It was found that about 5,800 ha area along the shoreline would be lost in 2030, while 11,200 ha would be recessed in 2075. It was also found that about 13,750 and 252,000 tons of food grain production would be lost in 2030 and 2075, respectively, due to shoreline erosion.

71

72 S.M.R. ISLAM, S. HUQ and A. ALI

1. Introduction

Bangladesh, situated at the interface of two different settings, is a disaster prone country. To the north of the country, lies the Himalayan range and to the south the Bay of Bengal and the Indian Ocean. These two different environment have made the country vulnerable to naturally occurring disasters like floods, droughts, cyclones and the accompanying storm surges, river bank and coastal erosion, salt water intrusion, etc. Bangladesh is overwhelmed with these types of disasters. Disasters bring immense miseries to the people. Lives are lost, properties are damaged and the development work is impeded. These result in slowing down of or retardation in the progress and prosperity of the country.

In the foreseeable future, another disaster is likely to inflict casualties in Bangladesh. This is the rise in sea level which is a consequence of global warming due to the increase the concentration of greenhouse gases in the earth's atmosphere. In addition to its direct effect, sea level rise (SLR) is likely to have multiple effects on the already occurring natural disasters in the country, thus further aggravating the disastrous situation prevailing in the country. A brief discussion was made on the impacts of SLR on the naturally occurring disasters in Bangladesh (Ali and Ahmad, 1992). In this paper, we deal with the impact of SLR on coastal erosion.

The area considered for impact study is the east coast of Bangladesh. Sea-shore recession due to SLR has been calculated with the help of Brunn's (1962) formula. For calculating the recession, field data have been collected for the aforesaid sea coast. Details of the data collection processes, analysis and results are given and discussed here. It has been found that the shoreline recession agrees reasonably well with results obtained elsewhere in the world.

However, to put the results and discussions into perspectives, it is worth giving here some outlines of the geomorphological conditions of Bangladesh coastal area as well as some review of the erosion work done for Bangladesh.

2. Coastal Morphology of Bangladesh

Bangladesh is drained by a large network of rivers centering one of the largest river systems in the world: the Ganges, the Brahmaputra and the Meghna (GBM). The GBM carries about 2.4 billion tons of sediments per year (Holeman, 1968) into the Bay of Bengal. These sediments interact with dynamic processes in the Bay leading to accretion in one place and erosion in the other. A huge amount of sediments are also thought to be carried by under currents into the deeper Bay of Bengal and the Indian Ocean.

The bottom topography of the Bay of Bengal plays a dominant role in the dynamic processes in the north Bay and Bangladesh coast. This topography is characterised by the

BEACH EROSION 73

Ninety East Ridge to the west of which lies the Swatch of No Ground (a submarine canyon) and the Bengal Deep Sea Fan. To the east are ·the Myanmar trench and the Nicobar Fan. In most of the northern Bay, particularly in and near the Meghna estuary, the water is shallow which helps amplification of waves like storm surges and tides. The bottom topography greatly influences the circulation pattern in the Bay.

The main features of this circulation: a western boundary current (WBC) runs northward and almost in parallel to the west coast of the Bay and it deflects eastward at the head Bay somewhere near 18-20°N latitudes and breaks into cyclonic and anticyclonic gyres. These gyres may be partly responsible for balancing the northward mass transport by the WBC by a compensating southward transport through the eastern part of the Bay of Bengal (Ali, 1991). There may be some under currents also being generated/influenced by the Swatch of No Ground (Curray and Moore, 1974). A persistent warm water zone is also observed (Huh et al., 1985) along the Myanrnar-Chittagong coast. The Bay dynamics is also controlled, particularly at the head Bay, by the river discharge through the GBM river system. This discharge apparently breaks (as is apparent in satellite imagery) into two branches: one moves south-westward and seems to be governed by the Swatch as well as the Coriolis force (Ali, 1995) while the other component moves southward along the Chittagong coast and it may be joined by the gyres.

According to Ali (1991) the salient and major features of coastal morphology of Bangladesh are:

• Low coastal bottom topography

• Low coastal land topography

• A large network of rivers, canals and streams

• A huge discharge of river water heavily laden with sediments

• A deep submarine canyon called Swatch of No Ground apparently controlling to a great extent the flow dynamics

• A funnel shaped Bay converging northward and meeting the Bangladesh coast

• High wind and tidal actions

• Frequently occurring tropical cyclones and storm surges

• A vast tract of mangrove forests influencing the flow dynamics

• A large continental shelf particularly near the Meghna estuary.

Under the given conditions of geomorphological features, circulation dynamics, topographical settings, coastal configuration, hydrological regimes/features, etc., the coast of Bangladesh has been divided into three distinct regions - the eastern, central and western regions (Prarnanik, 1983; UN ESCAP 1987). Figure-1 shows the three distinct coastal zones and the general region-wise descriptions are given below.


FIGURE 1. Map of Bangladesh showing three regions of coastal area.

KM

Regioo

LEGEND International Boundary BAY OF BENGAL

District Boundary

Coastal Island

- Coastal Regions

200

' ' .,. l ' \

BEACH EROSION 75

2.1. EASTERN REGION

Ibis region runs from Big Feni river to Badar Mokam (southern tip of the mainland Bangladesh) along Chittagong - Cox's Bazar coast. The east coast is more or less regular and unbroken and protected from the sea by mud flats and sandy shores. A long sandy beach of about 145 km runs from Cox's Bazar to Badar Mokam. Ibis region, particularly its southern part, is less vulnerable to sea disasters like storm surges. The noteworthy rivers that cut across the coast are Kamaphuli, Sangu, Matarnuhuri and Naaf. The Myanmar Trench, a submarine canyon, which protrudes northward and which is an extension of the Sundra Trench, plays a significant role in the dynamics of this region. The present study concentrates on the erosion phenomenon due to sea level rise in this region.

2.2. CENTRAL REGION

The central region lies between the Tetulia river and the Big Feni river, including the Meghna estuary. The region is characterised by heavy sediment load and fresh water discharge, accretion and erosion, highly broken coastline, a. series of small and big islands and a number of channels and rivers. The area has a large and extended continental shelf with shallow depth. Ibis is the most active coastal region of Bangladesh and here tropical cyclones and storm surges bring about most catastrophic ravages.

2.3. WESTERN REGION

Ibis region covers the area west of Tetulia river and upto the international boundary with India. Ibis region is relatively stable and covered by a large tract of mangrove forests. To the south of the western region lies the submarine canyon Swatch of No Ground which largely controls the flow dynamics in the northern Bay of Bengal. Ibis area has less erosion activity.

3. Review of Erosion Studies in Bangladesh

Erosion is a worldwide phenomenon. About 70% of the world's coastline has shown a net erosion over the past few decades, less than 10% has net degradation and the remaining 20% or so have remained relatively stable (Bird, 1985). For Bangladesh, studies are scattered depending on the particular pw.poses in most of the cases. A brief overview of some of the accretion - erosion studies done for Bangladesh coast is given below:

Miah (1975) made a qualitative discussion on the accretion and erosion problem in the Meghna estuary covering the period 1779-1975. Jabbar (1979) made a qualitative assessment of accretion/erosion by comparing the Survey of India Map of 1931 and a Landsat map of 1977. It was found that during the period a net accretion of 493 km2 took place in the mainland. Ibis was however the result of the building of a cross dams for reclamation of land. Erosions were observed in a major islands, namely Bhola (accretion


85 km2 and erosion 376 km2), Hatiya (accretion 64 km2 and erosion 172 km2), Sandwip (accretion 35 km2 and erosion 227 km2). During the period, many small chars such as Char Udaykal and Char Clark were completely eroded and some new chars like Char Dhal, Char Shabani, Nijhumdwip were formed.

Prarnanik et al., ( 1981) made a comparative study of seven different maps of the coastal region between 1779 and 1979. The results of the study are summarised in Table-1. It is observed that while the islands Hatiya, Sandwip, Shahbazpur, Manpura and others decreased in area, the mainland increased in size due to construction of cross dams. It is to be noted that around 1950 Hatiya island got larger and then it broke into two islands, the northern one joined the mainland.

TABLE 1. Land area in the Meghna Estuary (in sq. km)

Year Map Source Hatiya Sandwip Shabazpur Manpura Others Mainland Total

1779 Delta of Ganges 370 479 730 179 150 2789 4697 (Renne!)

1896 Survey oflndia 469 502 800 39 60 2370 4240 1945 Survey oflndia 1070 500 549 70 70 2650 4909 1959 Aerial 1030 391 339 80 101 2650 4591

Photograph 1973 Landsat-! 399 290 300 119 91 3900 5099 1976 Landsat-2 399 269 300 130 98 3999 5195 1979 Landsat-3 370 290 347 119 70 4100 5296

Source: Pramanik eta/. 1981

A detailed computer analysis of Landsat data for the years 1972 and 1979 was made by Pramanik (1983) for the coastal region. This study, however, showed a net accretion of land by about 213 km2 during the period 1972-79. Erosion was observed to be taking place in the north-eastern part of Bhola, northern part of Hatiya and north-western part of Sandwip.

A SPARRSO (1987) study on coastal dynamics of Bangladesh for the period 1960-84 showed a net erosion. The amount of land accreted and eroded for major islands is given in Table-2, which shows a net loss of about 844 km2•

TABLE 2. Change detection study for the period 1960-84 (in sq. km)

Name oflsland Accretion Erosion Net Result Bhola 80.06 360.76 280.70 (Erosion) Hatiya 30.86 108.44 77.58 (Erosion) Sandwip 0.0 110.46 110.75 (Erosion) Manpura 21.29 99.30 78.45 (Erosion) Sundarbans area 78.02 375.65 297.63 (Erosion)

Source: SPARRSO Report, 1987

BEACH EROSION 77

A study by Pramanik (1988) compared the Landsat imagery of 1972 and 1987 and found

that major erosion occurred at south-eastern and southern part of Sandwip, northern part of

Hatiya and north-eastern and north-western part of Bhola. A summary representation of

this study is given in Table-3. The chars and islands show a net erosion. A total of 11

chars/islands totally disappeared. About 40% of the land accreted in the mainland

appeared to have come from the reduction of river widths which seems to be precarious

for flood discharge because this may slow down the discharge of flood water into the Bay

of Bengal.

TABLE 3. Areas of mainland and·char/islands and number of chars/islands in 1973 and 1987 (in sq. km)

Item 1973 1987 1973-1987

Mainland 19,498 19,996 498 (accretion) Chars/islands 3,534 3,338 196 (erosion) No. of chars/islands 50 39 11 (loss)

Source : Pramanik, 1988

Siddique (1988) has given some erosion rates for different islands. This rate had been

about 150 rn/year between 1940 and 1982 for Hatiya. The northern tip of Hatiya which

was almost stable during 1940-63 showed a severe erosion rate of about 400 rn/year

during 1963-82. The Sandwip island had a rate of erosion of about 200 rn/year between

1913 and 1963 which increased to 350 rn/year during 1963-84.

MCSP (1992) made an accretion/erosion study for the whole coastal region of

Bangladesh. The study made a review of maps of the last few hundred years and made a

comparison of eroded and accreted land between the years 1971 and 1991. The study also

made a prediction/projection of erosion and accretion in the coastal area of Bangladesh for

the next 25 years.

In a later work undertaken by SPARRSO (1993), accretion and erosion were studied for

(i) the entire coast, (ii) the Meghna estuary and (ii) two small islands - Srizonee and Char

Montaz. The study period considered was 1976-90 and the study was made using remotely

sensed data. The results of study are shown in Table-4. It is ·seen that accretion and erosion

in the entire region as well as in the Meghna estuary are comparable. But accretion is quite

significant in Srizonee and Char Montaz and in the surrounding areas.

TABLE 4. Comparative statement of erosion and accretion

Location Scale Period Erosion (sq. km) Accretion (sq. km)

Entire coast 1:500,000 1976-1990 858 808 The Meghna Estuary 1:250,000 1976-1990 764 744 Srizonee and surroundings 1:50,000 1984-1990 24 58 Char Montaz and 1:50,000 1984-1990 5 39 surroundings

Source: SPARRSO, 1993


It is apparent from the above-mentioned studies on accretion and erosion that neither accretion nor erosion is of alarming rate. Both are compensating each other to a reasonable extent.

4. Erosion Dynamics or Causes of Erosion

Whatever may be the net result of the accretion/erosion process, it is very difficult to identify separately the contribution to erosions due to different dynamic causes of erosion. The main causes of coastal erosion m Bangladesh are:

• Heavy discharge current

• High astronomical tides

• Strong monsoon water current

• High storm surges

A brief description on the possible impacts of SLR on erosion via media the abovementioned four major causes of erosion in Bangladesh will be made here (Ali, 1989). The erosion theory will be discussed in the next section.

4.1. DISCHARGE CURRENT

A huge amount of water discharges through and from Bangladesh into the Bay of Bengal. The main thrust is on the Meghna estuary at the north-east comer of the Bay of Bengal. The strong discharge current causes considerable erosion in the coastal area. The SLR will push the coastline as well as the river mouth landward and is likely to modify the discharge current and hence the erosion. The 1.5 m contour line is very near the coastline in the Meghna estuary. The 4.5 m contour is also quite near. As a result the gradient flow may increase and also the erosion. However, there are a lot of uncertainties about this. The mechanism thus needs to be explored.

4.2. TIDE

Tide is another major cause of coastal erosion in Bangladesh. It is mostly semi-diurnal in character and shows an increase from the Indian coast in the west to the Meghna estuary where it is the highest (range is as high as 5 m or so on the average). Then the tide shows a gradual decrease in the south-east direction along the east coast of Bangladesh (Ali, 1996). Tides in the Bay of Bengal originate in the Indian Ocean and get amplified at the Head Bay due mainly to nonlinear shallow water effect and the northward convergence of the Bay of Bengal. The high tidal water action thus contributes to the erosion problem in Bangladesh. The rise in sea level is likely to increase the tidal range ·in the Bangladesh coast. This has been demonstrated by Flather and Khandkar (1987) through numerical modelling. Furthermore, the inundation due to SLR may increase the nonlinear effect and hence increase the tidal range, thereby increasing the erosion effect.

BEACH EROSION 79

4.3. MONSOON CURRENT

The south-west monsoon wind that flows over the Indian Ocean and the adjoining land areas generates strong water waves and water current in the area. The water waves and water current cause heavy erosions in Bangladesh coast, particularly in the Meghna estuary where water rises due to piling up of water by south-west wind (Ali, 1995). The wind also stirs the water in the shallow coastal area almost over the whole depth. The result is erosion. The areas likely to be inundated by SLR may be subjected to wind effect, thereby causing more erosion in the area.

4.4. STORM SURGES

Storm surges are generated by cyclones forming in the seas and oceans. Tropical cyclones forming in the Bay of Bengal and the associated storm surges combined together cause innumerable losses to the life and property in Bangladesh. The storm surges in Bangladesh are among the highest in the world. These are greatly responsible for changes in the coastal configuration, causing erosion and accretion. Global climate change and the sea level rise are likely to influence the cyclone activity and storm surge phenomenon. Possible impacts of climate change and sea level rise in the context of Bangladesh have been discussed, among others, by Johns and Ali (1987), F1ather and Khandkar (1987), Pramanik and Ali (1989), Ali and Ahmad (1992) and Ali (1996). Ali (1996), using a storm surge model for the Bay of Bengal, has given different scenarios of cyclone and storm surge activity in Bangladesh with respect to April 1991 cyclone that took a death toll of about 138,000 in Bangladesh.

It may be said that if cyclone activities and storm surges change due to climate change, the erosion problem is likely to be more aggravated.

5. Theory of Erosion Due to Sea Level Rise

The sea level rise is one of the driving mechanisms of coastal erosion. While this has an indirect effect on coastal erosion through the dynamical processes, it itself has a direct contribution to erosion as well. With a rise in water level, the coastal morphological system will adjust itself to the high water level situations by creating a new coastal profile at a higher level at the coast of the presently existing coastal profile. This process, as described by Vellinga (1986), is as follows:

a) By a rise in water level, the water line will shift landward.

b) As the coastal profile becomes steeper, erosion will occur until a new dynamic equilibrium is reached at a higher level.

c) The natural filling rate of lagoons and tidal basins will increase with an accelerated rise in sea level; the sediments required for the filling will come largely from the surrounding areas through erosion.


d) Rising sea level will cause a shoaling effect in rivers as a consequence of which (shoaling) sediment yields from rivers will reduce; these sediments will not be available to compensate for any erosion in the coastal area.

We shall discuss here the theory of erosion due to sea level rise, following mostly the method developed by Brunn (1962).

The erosion phenomenon due to sea level rise is depicted in Figure-2. The figure shows the present coastal profile with respect to the present mean sea level. Higher sea levels will result in coastal recession because· the waterline will shift landward due to submergence. Not only this, erosion will occur, as pointed out before, until a dynamic equilibrium is reached and a new coastal profile is formed. Figure-2 shows the new coastal profile under the future sea level rise situation. The continuous line is the present profile and the dotted line is the new profile after rise in sea level and after quantitative balance between shore erosion and bottom deposits. The eroded and sedimented areas are shaded. Amount of sediments eroded will be equal to the amount of sediments deposited, assuming that eroded sediments are not lost (iflost, then by an insignificant amount) into the deep sea.

FIGURE 2. Erosion phenomenon due to sea level rise

WAlER

b

..------- b --------., ....

If 'a' is the rise in water level due to SLR, the quantity of sediments needed to re-establish the same bottom profile over a shelf width, 'b', will be 'ab'. This quantity must be derived from the erosion of the shore. This will give rise to a shoreline recession, 'x' . We consider

BEACH EROSION 81

that the shoreline is in longshore equilibrium as indicated above. That means the same quantity of material that is passing from the updrift side is also passing out downdrift. If the elevation of the shore is 'e', the quantity eroded above sea level is 'xe'. In the meantime, in order to reestablish the original equilibrium bottom-profile, the entire bottom profile must move shoreward by the same distance, 'x', upto depth 'h', at distance 'b' from the shoreline. The amount of eroded sediments will be 'x' (e+h). Under a balance between the eroded and deposited sediments, we have

x(e+h)=ab ooooooOOOOOOOOOOooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo (1)

ab or x = ----------- 000000 00 0000 00000000 00000000000000 000000 0000 000000 0000000000 00 00000000 000000 00000000 (2)

e+h

Thus, if values of the parameters on the right hand side of the above equation (2) is known, then the erosion due to SLR can be calculated. The application of this formula has given reasonable results for the Pacific and the Atlantic coasts.

Ali and Ahmad (1992) and Ali (1994) have made a rough test of the formula for the west coast of Bangladesh. Using e = 1.0 m, h =20m, b = 60,000 m (typical of the west coast of Bangladesh) and a= 1.0 cm/yr, it was found that the formula gives a shoreline recession through erosion of about 2.9 m/yr. This value will be even larger for the Meghna mouth where b is larger. The value x for west coast is about 3000 times the SLR and seems to be very large compared to other places in the world. For example, erosion is about 100 times the sea level rise for the Florida coast (Brunn, 1962). For Belgium to Denmark, the erosion figure is estimated to be between 60-80 times the SLR (Hekstra, 1989). Vellinga (1988) estimates that a sea level rise of 1.0 m will cause an erosion of a sandy shore in the order of 100-500 m. So it was concluded by Ali and Ahmad (1992) that the Brunn's formula is not suitable for application to Bangladesh.

However, the conclusion by Ali and Ahmad (1992) was based on the rough estimate for the west coast of Bangladesh where the continental shelf is very wide and gently sloping. In fact, as stated by Brunn (1962), and as it appears from the equation, the formula is valid and more applicable for an area with a steep bottom profile. Additionally, as stated by Leatherman (personal discussion) the Brunn's formula is more applicable for sandyshores. Such a situation exists on the eastern (Chittagong-Cox's Bazar) coast of Bangladesh. The data collected and results given in this report refer to the east coast of Bangladesh. So the present study concentrates on the application of Brunn's formula for the eastern sandy shore of Bangladesh

In passing, it may be of some use to have a feel of the erosion numbers for Bangladesh under different SLR scenarios. Using an erosion range of 100 to 500 times the SLR, Ali and Ahmad (1992) have made some estimates of erodible areas in Bangladesh due to SLR. This is given in the Table-5.


TABLE 5. Erosion due to SLR for two different erosion rates (area in sq. krn)

SLR(m) Erosion = 1 00 times SLR

1.5 3.0 4.5

Source: Ali and Ahmad, 1992

6. Survey and Study Area

55 265 447

Erosion= 500 times SLR

275 1,375 2,235

The study area is shown in Figure-3. This area has been selected by considering the better applicability of Brunn's formula. The study area is bounded by latitudes 20° 40' N and 22° 13.5'N and longitudes 91° 45'E and 92° 2'E. The administrative Thanas Banskhali and Anwara of Chittagong district and Teknaf, Ukhia, Ramu, Cox's Bazar and Chokoria of Cox's Bazar district are covered by the study area. Almost the whole of the east coast of Bangladesh is included in the study.

6.1. FIRSTPART

The first part starts from Shahparidwip (Teknaf) to the confluence of the Bakkhali Khal (Cox's Bazar). The soil of this area is sandy-silt with bright colour. The slopes in this part are developed and mild. The hills are situated to the nearest coastline in this part.

It can be mentioned here that Bangladesh has been divided into twenty-four sub regions with fifty four units on the basis of physical features and drainage pattern based on Slate (1954) physiographic classification of the Bengal Basin (Rashid, 1991). The first part of the study area is comprised of three of them as follows:

6.1.1. Bakkhali River Valley This valley has two parts, the upper one forms part of the Idgarh-Gorjania valley and is just a small section of the southern hills. The lower valley is, however, a distinct break in the western part of these hills. It is 32 km long and varies from one to sixteen km in breadth. Its silt has badly affected navigation in the Moishkhali channel into which it falls.

6.1.2. Southern Beach Plain The beach plain is so called because its main feature is the continuous line of sandy beaches and sand dunes backed in places by narrow coastal plains and almost throughout by hills. It extends from Bakkhali river mouth south to the Rengadurnakhal, a distance of 105 km. It is cut across by several streams, of which the Rejukhal Monkhali and Silkhali are major ones. This coastal plain varies in width from 100 meter at Patuartek (Elephant point) to over a km near Shilkhali. There are cliffs at Bhangamura, 11 km south of Cox's Bazar, where the sea is eroding a part of the Teknaf range. Evidently the hills north

BEACH EROSION

FIGURE 3. Map of Bangladesh showing study area

\. ,; I

BAY OF BENGAL

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District Boundary

Coastal Island

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83


and south of Bhangamura formerly eroded. At Patuartek and Borodeil, the Teknaf range makes headlands, thus forming slight bays at Inoni and Shilkhali. This is evidently a coastline submergence.

6.1.3. Nhila-TeknafPlain The hill wash brought down by the tributaries of the Naaf river (an arm of the sea) has formed two coastal plains. Soil of these two plains is heavy clay except for a sandy central ridge in the southern part. The effects of the tides are of great importance to agriculture and the Nhila plain's sudden floods from the hills streams are a hazard. The upper Naaf is silting rapidly (Moishkhali channel).

6.2. SECOND PART

This part lies between frrst part and third part which may be called channel-bank line region starting from the confluence of the Moishkhali Channel to the intake of the Kutubdia channel at the Bay of Bengal near Khudukhali ofBanskhali Thana in Chittagong district. The soil of this part is ahnost clay containing organic materials. This part has been developed as shrimp-culture area. The slopes are flat i.e. mud flat area.

6.3. THIRD PART

This part is similar to that of the first part. Only difference is that the rate of bank erosion (sea-shore) is very high. There is no existence of hills near sea-shoreline. The slopes are comparatively steeper than that of the frrst part. The soil of this part is sandy clay.

7. Data Collection

A field survey was made of the east coast of Bangladesh. Data were collected for 21 crosssectional points along the coast. The sections are shown in the Figure-4. The data included the depths and elevations at different points along each cross-section. The survey period was 3-15 August 1995.

7.1. METHODOLOGY OF TAKING READINGS

The total shoreline has been divided into 20 divisions with more or less equal latitude values, i.e. 4' to 5' intervals.

The following methods were maintained in collecting data.

• Taking of readings began from the southern part of Teknaf Thana in the Sabrang Union because it was not possible to go to the Shaparidwip of the same Thana due to rough weather during that time of the year.

BEACH EROSION 85

• Readings were taken perpendicularly to the waves which normally dissipated at the sea beach.

• The bearing of each point of observation was taken accordingly.

• The description of each point was recorded in brief.

• The latitude and longitudinal values of each point were measured using Global Positioning System (GPS).

The zero or reference level was taken as the highest spring tide level. The information on spring tide level was obtained from the responsible local people and debris deposition marking. However in applying the depth/height contour in Brunn's formula, the reference level was converted to mean sea level (MSL) by taking into account the average ranges of M2 (lunar semi-diurnal) and S2 (solar semi-diurnal) tides which are the most dominant tides in this region. The I m (negative/positive) elevation with respect to the corresponding distances and elevation at 50 m intervals in both ways (land side/sea side) was taken.

TABLE 6. Coastal recession due to SLR based on field survey, August 1995

Section/ Depth Elevation Distance Recession (m) Point No. (m) (m) (m)

h e b x (em) 100 75 30

3.24 3.20 836.00 129.81 90.87 38.94 2 2.88 4.20 760.00 107.34 75.14 32.20 3 3.60 3.80 494.00 66.76 46.73 20.03 4 1.80 4.25 380.00 62.81 43.97 18.84 5 1.80 1.50 494.00 109.78 76.84 32.93 9 2.52 3.00 494.00 89.49 62.64 26.85 10 2.52 4.00 380.00 58.28 40.80 17.48

Note : Extent of sea level rise is shown in Italic form

8. Data Analysis, Results and Discussions

Using the field data, profile ofbottom topography for each section was drawn. Out of the 21 sections, only 7 (sections 1,2,3,4,5, 9 and 10) have sandy shores. Sections 6-8 are hilly areas. The rest of the sections have embankments, where landward side is deeper than the seaward side. If the sea level overtops the embankments, erosion situation like (c) may occur, i.e. the depressed land behind the embankment will go under water due to SLR and the natural filling rate by sediment will increase and the sediments required for filling will largely come from the surrounding areas through erosion. The area considered for calculation is shown in Figure-5.

Since the Brunn's formula is more applicable for sandy shore, the formula has been applied only to the sandy sections. The distance 'b' and depth 'h' have been calculated


FIGURE 4. Map showing cross sectional points

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BEACH EROSION 87

from the Admiralty Charts and the elevation 'e' has been calculated from the profiles. The recession distance 'x' has been calculated for three values of SLR 30 em, 75 em and 1.0 m. The results are shown in tabular form in Table-6. For 30 em rise in sea level, the erosion values vary from about 18 to 39 em, for 75 em, the variation is from about 41-91 em and for 100 em, 58 to 130 em. It can be said that the results compare reasonably well with the world figures as mentioned earlier.

Table-7 gives the recession in m per 1 em rise in sea level for all the 7 points given in Table-6 and for the three SLR values, it is 30 em, 75 em and 100 em, respectively. These values of recession have been calculated by dividing the recessions given in Table-6 by the corresponding rise in sea level. It comes out that, on the average, a recession of 0.87 em occurs per 1 em rise in sea level, ie. 87 em per 1 m rise. That is, recession distance through erosion due to SLR is 87 times the SLR.

TABLE 7. Recession distance per 1 em rise is sea level for three cases of 30 em, 75 em and I 00 em SLR

Point No. Recession (m) /em SLR

IOOcm 75 em 30cm 1.298 1.210 1.298

2 1.073 1.001 1.073 3 0.667 0.623 0.667 4 0.628 0.587 0.628 5 1.097 1.024 1.097 9 0.895 0.835 0.895 10 0.583 0.544 0.583 Mean 0.892 0.832 0.892

Figure-6 shows the coastline position of the present and for the 2030 and 2075 corresponding to sea level rise of 30 em and 75 em, respectively for three different locations A, B and C shown in inset. These are representation of the possible coastline positions in future under different SLR scenarios. Table-7 and Figure-6 indicate that recession rate is more or less uniform throughout the coastal area under study.

Most of the areas under study on erosion are agricultural land. An estimation has been made of the total loss of land due to erosion. This is given in Table-8, which also shows the loss of agricultural land. It is estimated that about 5.8 km2 and 11.2 km2 of land will be lost due to SLR of 30 em and 75 em respectively. The corresponding loss of agricultural land will be about 5.5 km2 and 10.8 km2 .

TABLE 8. Loss of land due to SLR

Sea level rise

30cm 75 em

Total land loss (ha)

5,800 11,200

Agricultural land loss (ha )

5,500 10,800


FIGURE 5. Map showing section considered for calculation

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Study Area

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BEACH EROSION

FIGURE 6. Map showing land recession due to sea level rise

LEGEND

Thana Boundary - Coast Line (Existing)

Coast Line (2030) -- Coast Line (2075) CK Olakaria CB Cox's Bazar UK Ukhia TK Teklmaf

Land

c

Land

Scale 1: 15,000 Scale 1: 1 5,000 Scale 1 : 15,000

89


The Brunn formula, as pointed out earlier, is well applicable for sandy shores. For clay soils or for hilly areas, the formula is not readily applicable. Bird (1985) has used a multiplying number on the right hand side of the equation (2), i.e.

ab x= k ------------- .................................................................................... ( 3)

e+h

With k= 1, equation (3) reduces to Brunn's formula. In the absence of a suitable value of k for Bangladesh, the equation (3) could not be used. But obviously, k will be less than unity for clay soil and hilly areas resulting in less erosion compared to the erosion for sandy shores.

9. Recommendations

1. Detailed topographic survey of the coastal area (both land and water) should be conducted. The land survey should have a high resolution topographic data. A high resolution topographic map will, among other things, help assess the coastal inundation due to small increments of SLR as well as other vulnerability.

2. A regular and routine detection of sea level change study of the coastal area of Bangladesh should be made.

3. The yearly highest tide level and the monthly lowest tide level should be measured for getting improved results.

4. The wind speed and velocity of waves for particular period (rough weather or cyclone involving period) should be recorded for shore erodible area.

References

Ali, A., 1979. Storm surges in the Bay of Bengal and some related problems, Ph.D. Thesis, University of Reading, England.

Ali, A. and Ahmad, A.A.Z., 1992. Impact of sea level rise on other disasters in Bangladesh. Presented in the IOCIUNEP workshop on Impact of Sea Level Rise due to Global Wanning for the South Asian Region held in Dhaka, Bangladesh, 16-19 December, 1993.

Ali, A. and Hoque, M.A., 1994. Mathematical modelling of back water effect in the Meghna river mouth in Bangladesh, The Journal of NOAMI (National Oceanographic and Maritime Institute), 11 No. 1, pp 27-33 .

Ali, A., 1990. Coastal erosion in Bangladesh and sea level rise. In the IOCIUNEP report of the Task Team on the Implications of Climate Changes and Impact of Rise in Sea level in the South Asian Seas Region, Karachi, Pakistan.

BEACH EROSION 91

Ali, A., 1991. Satellite observation and numerical simulation ofwestem boundary current in the Bay of Bengal, Presented in the 12th Asian Conference on Remote Sensing, Singapore, 30 October- 5 November.

Ali, A., 1995. Numerical investigation into the retardation of flood water outflow through Meghna river in Bangladesh due to SW monsoon wind. Estuarine, Coastal and Shelf Science, 41, pp 689-704.

Ali, A., 1996. Vulnerability ofBangladesh to climate change and sea level rise with special reference to tropical cyclones and storm surges. Journal of Water, Air and Soil Pollution, 92, pp. 171-179.

Bird, E.C.F., 1985. Coastline change, A global review, John Wiley & Sons.

Brunn, P., 1962. Sea-level rise as a cause of shore erosion. J. Waterways and Harbors Division, Proc. Am. Soc. Civ. Engg. 88, 117-130.

Curray, J.R. and Moore, D. G., 1974. Sedimentary and tectonic process in the Bengal Deep Sea Fan and Geosyncline. In The Geology of Continental Margins; C.A. Burk, and C.L. Drake (Eds.), Springer- Verlag, New York.

Duplessy, J.C., 1982. Glacial to interglacial contrasts in the Northern Indian Ocean. Nature, 295, 494-498.

Flather, R.A., and Khandkar, 1987. Effect of sea level rise on storm surges in the Bay of Bengal, Presented at the International Symposium on the "Effects of Climatic Change on the Sea Level, Severe Tropical Storms and Their Associated Impacts" held in Norwich, England, 1-4 Sept. 1987.

Frank, W.M., 1985. Tropical cyclone formation, in A Global View of Tropical cyclones, R.L. Elseberry (Ed), based largely on the International Workshop on Tropical Cyclone held in Bangkok, Thailand, 25 Nov-5 Dec. 1985.

Gray, W.M., 1980. Global climatological aspects of tropical cyclone occurrence. Pre-Print Volume, Symposium on Typhoons, Shanghai, China, 6-11 October, 1980.

Gray. W.M., 1985. Tropical cyclone global climatology. WMO Technical Document WMO/TD No. 72, I, WMU Geneva, Switzerland.

Hekstra, G.P., 1989. Global warming and rising sea levels: the policy implication, The Ecologist, 19, 4-15.

Holeman, J.N., 1968. The sediment field of major rivers of the world, Water Resources Research, 4(4).

Huh, O.K., Ali, A. and Quadir, D.A., 1985. Observation on the surface features in the Bay of Bengal with NOAA satellite A VHRR imagery. Technical Report, Coastal Studies Institute, Louisiana State University, Baton Rouge, USA.

Jabbar, M.A., 1979. Land accretion in the coastal area of Bangladesh, Report of Bangladesh Landsat Programme, Dhaka, Bangladesh.

MCSP, 1992. Multipurpose Cyclone Shelter Programme, Draft Final Report, Vol. XI, Special Studies, UNDP/World Bank/GOB Project BGD/91/025.

Meehl, G.A. and Washington, W.M., 1988. Tropical response to increased C02 in a GCM with a simple mixed layer ocean: similarities to an observed Pacific warm event, Mon. Wea. Rev.,114.


Miah, M.M., 1975. Changing morphology of the Ganges-Meghna delta, Proceedings of Bangladesh National Seminar on Remote Sensing, Dhaka, Bangladesh.

Miah. M.M., 1988. Flood in Bangladesh. Academic Publishers, Dhaka, Bangladesh, 108pp.

Pramanik, M.A.H. and Ali, A., 1989. Impact of greenhouse effect in the Himalayan region specially in the coastal region of Bangladesh. Presented in the seminar on State of Environment in the Himalayan Region, held in Dhaka, Bangladesh on 18 June, 1989.

Pramanik, M.A.H., 1983. Remote Sensing Applications to Coastal Morphological Investigations in Bangladesh, Ph.D. Thesis, Jahangimagar University, Savar, Dhaka, Bangladesh.

Pramanik, M.A.H., 1988. Methodologies and techniques of studying coastal systems. SPARRSO case studies, Presented at the National Development and Management, held in Dhaka, Bangladesh, 3-4 Oct., 1988.

Pramanik, M.A.H., Ali. A., and Rahman, A., 1981. An assessment the land accretion and erosion in the Meghna estuary, Presented at the Third National Geographical Conference held in Dhaka, Bangladesh.

Pramanik, M.A.H., and Ali, A., 1989. Impact of greenhouse effoct in the Himalayan region specially in the coastal region of Bangladesh. Presented in the seminar on State of Environment in the Himalayan Region held in Dhaka, Bangladesh on 18 June, 1989.

Rashid, H. E., 1991. Geography of Bangladesh, The University Press Limited, Dhaka, Bangladesh.

Schlesinger, M.E., and Mitchell, J.F.M., 1986. Climate model simulations of the equilibrium climate response to increased carbon dioxide. Rev. Geophys., 25, 760-798.

Siddiqui, M.H., 1988. Land accretion and erosion in the coastal area, Presented at the National Workshop on Bangladesh Coastal Area Resource Development and Management held in Dhaka, Bangladesh 3-4 Oct, 1988.

SPARRSO Report, 1987. Report on pilot project on remote sensing application to coastal zone dynamics in Bangladesh, Dhaka, Bangladesh.

SP ARRSO, 1993. Monitoring of changes in coastal zone area based on Landsat MSS and infrared aerial photographs, SP ARRSO Report, December 1993.

Spate, 1954. India and Pakistan : Methuen Co. London.

UN ESCAP, 1987. Coastal environmental management plan for Bangladesh, ST/ESCAP/618, 2.

Vellinga, P., 1986. Sea level rise consequences and policies, In Sea level Rise; A Selective Retrospection, Delft Hydraulics, The Netherlands.

VULNERABILITY OF FOREST ECOSYSTEMS OF BANGLADESH TO CLIMATE CHANGE


NEAZ AHMED SIDDIQI Chief Scientific Officer Bangladesh Forest Research Institute (BFRI)

RA WSHAN ALI CHOUDHURI Senior Fellow Bangladesh Centre for Advanced Studies (BCAS)

ABSTRACT

Bangladesh is endowed with a number of natural forest ecosystems including inland Sal forest, dipterocarp forest, savanna, bamboo bushes in the hilly regions and freshwater swamp forests. It also have littoral mangrove ecosystems. An attempt was made to qualitatively analyse the impact of climate change on forest resources of Bangladesh.

It was found that increased rainfall during monsoon would cause increased runoff in forest floor instead of infiltration into the soil. As a result there would be enhanced soil erosion from the forest floor. The erosion problem would be more pronounced in poorly dense hill forest areas. Prolonged floods would severely affect growth of many timber species, while it would cause high incidence of mortality for Artocarpus species. In contrast, enhanced evapotranspiration in winter would cause increased moisture stress, especially in ·the Barind and Madhupur Tract areas, affecting the Sal forest ecosystem. The tea plantations in the north-east would also suffer due to moisture stress. It was found that the Sundarbans mangrove forest would be the worst victim of climate change. Due to a combination of high evapotranspiration and low-flow in winter, the salinity of the soil would increase. As a result the growth of freshwater loving species would be severely affected. Eventually the species offering dense canopy cover would be replaced by non-woody shrubs and bushes, while the pverall forest productivity would decline significantly. The degradation of forest quality might cause a gradual depletion of rich diversity of the forest flora and fauna of the Sundar bans ecosystem.

93

94 A.U. AHMED, N.A. SIDDIQI and R.A. GHOUDHURI

1. Introduction

Bangladesh has one of the highest population densities in the world and hence practically all the land area (14.4 million hectares) is inhabited by human beings. Nevertheless, some 15% of its land is occupied by legal state forests while another 2% land is occupied by private forest. Owing to its unique geographical location between two biologically diverse sub-regions (Indian and Malayan) Bangladesh has a number of major natural forest ecosystems including the Sundarbans.

The forests of Bangladesh are under tremendous threat due to a number of anthropogenic and natural reasons. Increased consumption of forest products, human encroachment, deforestation and deliberate thinning combined with natural disasters, low flows in the distributaries of the Ganges due to withdrawal of water at Farakka barrage point in India during lean season and its consequences - all are causing serious problems on regenerative power and growth of the different forest species. In addition, climate change and sea level rise together would cause adverse impacts on the remainder of the forests. Since the productivity and well being of forest species depend on a number of climatic parameters including temperature and precipitation, there are reasons to believe that the forest ecosystems of Bangladesh would also be affected significantly due to impacts of climate change and sea level rise. This article examines the vulnerability of forest ecosystems of Bangladesh to global warming induced events with special reference to the Sundarbans forest.

2. The State of Forests in Bangladesh

According to the official sources the total land under forest is about 2.56 million hectares which include classified and unclassified state forest lands, village forest areas and private owned tea and rubber gardens (FMP, 1995). Table-1 presents official land area classification for Bangladesh. Natural forest and plantations occupy 31 and 13 percent of the forest lands, respectively. Regardless of the official and legal status of the forested lands, there exists only about 835,000 hectares of state owned forest vegetation of reasonable quality. This includes medium to good density natural forest, bamboo and plantations but excludes parks and sanctuaries. About 116,700 hectares forested area is currently being protected by the state. Table-2 presents classified and unclassified forest land by actual physical cover.

Forest ecosystems ofBangladesh consist mainly of natural and plantation forests. Natural forests are comprised of natural hill forests and inland Sal forest ecosystems. Plantation forests are, however, observed in deforested/degraded hills and Sal forests and also in the newly accreted low-lying coastal lands. A brief description of different types of forest ecosystems is presented below.

VULNERABILITY OF FOREST ECOSYSTEM 95

TABLE 1. Land area classification of Bangladesh

Landuse Category Area(Mha) Relative Area (%) Agriculture 9.25 64.2 Forest (total) 2.56 17.8

State forest Classified state forest 1.49 10.3 Unclassified state forest 0.73 5.1

Private forest Village/homestead forest 0.27 1.9 Tea/Rubber garden 0.07 0.5

Urban 1.16 8.1 Water 0.94 6.5 Other 0.49 3.4 Total area 14.40 100.0

Source: Forestry Master Plan, 1995

2.1. NATURAL HILL FOREST ECOSYSTEM

There are several types of different hill forest ecosystems: dipterocarp forest, savanna, bamboo and freshwater swamp forest. All these four types combined together constitute about half of the forests in Bangladesh.

2.1.1. Dipterocarp Forest The vegetation here comprises of mixtures of several tropical evergreen and deciduous tree species, mostly occurring in association with bamboo jungles. The canopy apparently has three stories: (i) the top storey is mainly comprised of Garjan (Dipterocarpus turbinatus) in association with civit (Swintonia floribunda), chundul (Tetrameles nudijlora) and narikeli (Sterculia alata) species; (ii) the middle storey is comprised of chapalish (Artocarpus chapalasha), nageswar (Mesua ferrea), pitraj (Aphanamixis polystachya), kamdev (Calophyllum Spp.), champa (Michelia champaca), tali (Dichopsis polvantha), bandarhola (Duabanga sonneratiodes), toon (Cedrela toona) etc.; and (iii) the bottom storey is comprised ofjarul (Lagerstroemia speciosa),jam (Syzygium Spp.), gamar (Game !ina arborea ), batna (Quercus Spp.) etc.

2.1.2. Savannas Savanna covers large part of unclassified state forest of the south-eastern hill tracts (see Figure-1 ). Its vegetation consists of tall grasses with scattered trees.

2.1.3. Bamboo Bamboo (Bambusa Spp.) occurs in abundance in association with major tree species. Although there are four major bamboo species present in the forests, muli (Melocanna baccifera) is the predominant species of all. Bamboo mainly occurs in the hills of Chittagong Hill Tracts and Sylhet.

96 A.U. AHMED, N.A. SIDDIQI and R.A. CHOUDHURI

FIGURE 1. Forest areas of Bangladesh

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2.1.4. Freshwater swamp forests Freshwater swamp forests are observed in foothill wetlarid areas of greater Sylhet and Mymensingh districts. The predominant species are hijal (Barringtonia acutangula), jarul (Lagerstroemia speciosa), barun (Crataeva nurvala) and pitali (Trewia nudifloira). Also associated with these are the wild rose of Bengal (Rosa involucrata), ban tulsi (Lippia geminata), baladumur (Ficau heterophylla) and other climbers.

TABLE 2. Classified and unclassified state forest land by physical cover (in hectares)

Forest Type Hill Sal Littoral Total Forest Forest Forest Areas

Natural forest (medium to good density) 85,136 374,899 460,035

Natural forest (poor density) 52,359 27,531 79,890

Scattered trees and denuded 57,593 25,386 82,979

Mainly bamboo 71,196 71,196

Plantation (including failed plantation) 197,714 21,386 112,966 331,766

Slash and bum and encroached areas 70,793 28,220 99,013

Unproductive (including bamboo areas) 11,779 6,250 18,029

Parks and sanctuaries 64,237 13,510 32,326 110,073

Water areas 31,980 170,000 201,980

Others including unclassified state forest 713,652 67,820 781,472

Total 1,356,439 121,983 758,011 2,236,433

Source: Forestry Master Plan, 1995

2.2. NATURALSALFORESTECOSYSTEM

Sal (Shorea robusta) is a typical tropical moist deciduous species found in abundance in an inland forest located north of Dhaka near Mymensingh (Figure-1 ). In the forest the associated species include palas (Butea monosperma), koroi (Albizia spp.), chapalish, bahera (Terminalia belerica), haritaki (Terminalia chebula), haldu (Adina cordifolia), sonalu (Cassia fistula), udal (Sterculia spp), kusum (Schleichera oleo/sa) etc. Several of these species are commonly known to have medicinal properties and widely used in Ayurvaidya (traditional medicine). Two thirds of the designated Sal forest area have been denuded/degraded due to human encroachment and illegal logging.

2.3. LITTORAL MANGROVE ECOSYSTEM

The Sundarbans is known as the single largest stretch of productive mangrove forest in the world. It is located in the northern limits of the Bay of Bengal and the estuaries of the Ganges-Brahmaputra-Meghna (GBM) river systems. It occupies an area of about one million hectares in south-west Bangladesh and south-eastern part of the State of West Bengal in hi.dia (between 88°85 and 89°55 E and 21°30 and 22°40 N). About 62% of the forest covering an area of 577,000 hectare is situated within the territory of Bangladesh,


the rest lies within India (Figure-2). About one third of the forest consists of water bodies in the forms of rivers, channels and tidal creeks. The forest land is highly influenced by tidal interactions because of the presence of these water bodies. The forest receives freshwater and sediment from a number of distributaries of the Ganges. It hosts one of the richest natural genepool for forest flora and fauna species in the world including the most notable one: the Bengal Tiger. The forest has been endowed with a number of commercially important mangrove species. The most common species are sundri (Heritiera fomes) from which the forest gets its name and gewa (Excoecaria agallocha). The other important tree species ,include goran (Ceriops decandra), golpatta (Nypa fruticans) and keora (Sonneratia apetala).

In general, dicotyledonous tree species are represented by 22 families and 30 genus, while Rhizophoraceae is represented by all the 4 known genera and at least 6 species. The shrubs are represented by 12 species belonging to 11 genus under 7 families. Eleven different species of climbers belonging to 6 families have so far been identified in the Sundarbans. In addition to the rooted plants, there are epiphytic parasitic flora found in the forest. Orchids of 13 species and ferns of7 species are identified in the Sundarbans.

2.4. PLANTATION FOREST ECOSYSTEM

In Bangladesh there are areas of long, medium and short rotation plantations in addition to the above mentioned natural forest ecosystems. Most hill forest plantations comprised of teak (Tectona grandis) with associated species, mainly jarul and gamar. There has been some fast growing eucalyptus plantation in the past two decades. The hill plantation areas have been shrinking due to deliberate thinning and deforestation~ In the flat regions, especially in the previously degraded Sal forest areas, there have been plantations with Sal and other indigenous species. In recent years there has been coastal plantations in the newly accreted low-lying lands.

2.5. VILLAGE FOREST ECOSYSTEM

Village or homestead forest ecosystems consist of mixed fruit, fuelwood, shade and other multipurpose tree species and bamboos throughout Bangladesh. At least 149 species of native and introduced trees have been identified in the village forest. Leuschner et a/., (1987) listed 30 tree species commonly found in the homestead forests. The top ten species were ranked as follows: bamboo, mango (Mangifera indica), jackfruit (Artocarpus heterophyllus), betelnut (Areca catechu), coconut (Cocos nucifera), mander (Erythrina spp.), koroi (Albizia spp.), rendi (Samanea saman), date pahn (Phoenix sylvestris), and jaam (Eugenia spp.). Every year more than 100 million saplings of different species are planted to enrich village forests. Although such forests do not belong to natural forest category, with increasing depletion of natural forests, village forest will become important habitat for many flora and fauna in future.

VULNERABILITY OF FOREST ECOSYSTEM

2.6. FORESTFAUNA

99

Forests of Bangladesh also house a variety of wild animals, birds, reptiles and the water bodies host a large range of sweet and brackish water fish, shrimps, crabs, mollusks, shellfish, turtles and snakes. Some fish and shrimp species provide edible protein to the diet of millions of people, while shrimp is exported abroad to earn foreign currency. The important animals include the spotted deer (Axis axis), giant estuarine crocodile (Crocodylus porosus), gharial (Gavialis gangeticus), wild boar (Sus scrofa), Indian otter (Lutra perspicillata), Asiatic elephant (Elephas maximus), and the most notable one- the Bengal Tiger (Panthra tigris tigris). By enacting a Wildlife Preservation Act, the Government has recently banned indiscriminate killing of these valuable wildlife species.

2.7. FOREST PRODUCT REQUIREMENT AND PRODUCTIVITY

Although an average Bangladeshi requires nominal amount of forest products, the total annual requirement and consumption of forest products from internal sources is significant. Since cooking in rural Bangladesh is predominantly done by using biomass fuel, about 48% of which originates in forests and is utilised in the form of fuelwood, branches, tree wastes and bamboos (FMP, 1995). On an average the annual consumption of forest products for cooking is estimated at 30 million tons. It is estimated that about 6.2 million cubic meter fuelwood was supplied in 1993 against a demand of about 8.3 million cubic meters. It is, however, believed that the consumption of fuelwood for domestic cooking has been declining. It is also estimated that the Sundarbans forest provides about 0.3 million tons offuelwood annually (FMP, 1995).

In rural Bangladesh sawn wood and round timber are used for a number of usages: building material, furniture and fixture, transport equipment, agriculture implements and other purposes. It is estimated that the 1991 demand for sawn and round wood for household and industrial consumption was about 4.27 and 0.2 million cubic meters of round wood equivalent, respectively. However, the total supply of the same in 1993 was estimated at about 1.29 million cubic meters of round wood equivalent. In addition, the total demand for poles and posts for 1991 was estimated at 0.26 million cubic meters, whereas the estimated supply was about 0.15 million cubic meters.

Other than the above mentioned uses a large quantity of pulpwood is used annually for the production of paper and other fibrous materials. Most of the pulp is imported, while over 46 thousand tons of newsprint has been consumed in 1991 from local production. It is to be mentioned here that most of the used newsprint and paper are recycled several times for different usage and fmally burnt for cooking. Adding all the above mentioned uses of forest products, the estimated demand for 1993 has been 13.48 million cubic meters, while 7.90 million cubic meters has been met from local forest production (FMP, 1995).

The annual rate of net deforestation mentioned in the Forestry Master Plan suggests that the present production of the forests can no longer support the rate of forest product


consumption. With increasing population, the demand will automatically increase and the remaining forests will be stressed further. It is, therefore, imperative to realise that the looming threats to the remaining forests due to increasing demand for forest products will be compounded by the threats associated with climate change.

FIGURE 2. The Sundarbans forest

o_-=z,.o __ 40m

LEGEND

- · - International Boundary

-~River ·.~ Sundarbans

2.8. DEFORESTATION AND FOREST DEGRADATION

During the past few decades the forests of Bangladesh have been disappearing at an accelerated rate due to increase in population and demand for forest products. A recent study reported that the annual forest cover area shrunk by some 37,600 hectares between 1980 and 1990 (FMP, 1995). During 1985 to 1992 the Chittagong Hill Forest area having good to medium density forest declined by 10,000 hectares, while another 7,000 hectares of natural forest in Cox's Bazaar disappeared during the same time. As of 1989 only about 17% of the total legal Sal forest areas remained across the central and north-west Bangladesh. In the Sundarbans, only two thirds of the total forested area had canopy


closure of 70% or more in 1984, while the rest of the forest had poor canopy density (Chaffey et al., 1985).

In recent years, however, a successful government-run media campaign for planting trees made the plantation programme a popular annual affair. The government's effort has been further strengthened by active participation of the non-government voluntary organisations. As a result a reversal of trend is now observed all around the country. It is believed that due to government's continued programme to attract community participation and benefit sharing activities the current alarming rate of deforestation will be reversed successfully. On the other hand, the complexity caused by the climate change impacts will counteract and negate the anticipated advancements.

3. General Impacts of Climate Change on Tropical Forests

The root cause of global climate change is the increased concentration of GHGs including carbon-di-oxide in the atmosphere. Increased ambient carbon-di-oxide levels would have positive influence on vegetative (single leaf-area) growth of forest species in general (Wullschleger et al., 1995). However, there exists some counter argument that the initial benefit may be negated by the various feedbacks in the plant and soil (Komer, 1993).

The response of forest species to climate change is diverse and complex. According to IPCC Second Assessment Report, tree species would certainly respond to altered temperature and water availability conditions (Kirschbaum et al., 1996). Generally, there is a positive correlation between net primary productivity and warming. However, with increasing water stress the potential growth responses would be negated. Scientific literature is yet to reveal the extent of compensation offered by increased water-use efficiency with respect to increasing carbon-di-oxide concentration. Moreover, increasing temperature would cause increasing range of insect pests that would have limiting effects on growth due to warming.

Although increasing temperature may lead to higher net primary productivity, net ecosystem productivity may not increase, and may even become negative, warming induced increased decomposition of soil organic matter (Kirschbaum, 1995). On the other hand, enhanced decomposition of soil organic matter also should have the effect of mineralising nutrients and making those available for the plants (Melillo et al., 1993). All such effects and counter effects would play respective roles in determining the potential of ecosystem specific species in a warmer world.

Computer simulation studies suggest that the productivity of tropical forests in different areas are likely to increase or decrease in accordance with changes in rainfall (Raich et al., 1991). Species in moist tropical forests are the least drought-adapted in the tropics and their survival will be at risk under climate change. On the other hand, increased rainfall runoff in open forest areas, especially in the hilly areas, will cause increased top soil


erosion and leaching. As a consequence there will be a net decrease in growth rate, biomass and diversity of forest species (Whitmore, 1984; and Jordan, 1985).

4. Impacts on Forests in Bangladesh

Although there exists a healthy international literature on response of different types of forests and biomes to climate change impacts, very little has been known on the same for Bangladesh. There is almost no systematic research on impacts of climate change on specific forest species. A recent study highlights the adverse impacts of climate change induced salinity intrusion on the Sundarbans mangrove ecosystems (Ahmed, 1998). In order to examine the vulnerability of different types of forest ecosystems, it is necessary to understand the general impacts of climate change on physical systems of the country.

It has been mentioned elsewhere that, in Bangladesh climate change would cause increased ayerage surface temperature throughout the year, especially in the early monsoon. Moreover, there would be significant increase in monsoon rainfall, following a decrease in winter. A combination of such changes would cause a net increase in evapotranspiration in the winter months at an extremely high rate (Ahmed and Alam, 1998). All such effects on primary physical systems would have significant impacts on natural forest ecosystems of Bangladesh.

Since the tree canopy of the natural forests in Bangladesh is becoming less dense, as discussed earlier, with increased rainfall in the monsoon, it is expected that there would be enhanced runoff in the forest floor instead of infiltration into the soil. Such an effect would be more pronounced in hill forest areas in Chittagong Hill Tracts (Figure-1). As a result, there would be higher possibilities of enhanced top soil erosion and overall habitat degradation of the forest ecosystems. The hill forest ecosystems would, therefore, become vulnerable due to impacts of climate change.

Increased runoff would also cause recurring floods in many areas of the flood prone country (Alam eta/., 1998). Enhanced flooding with longer than usual residence time for flood-water would have limiting effect on growth and survival of many indigenous species of village forest. In general, the effect would be most devastating for Artocarpus species. Artocarpus heterophyllus, the tree that bears national fruit and found mostly in relatively upland areas is intolerant to prolonged flooding. Other such species include Azadirachta indica, Cajanus cajan, Leucaena /eucocephala etc. (FMP, 1995). However, a few other species might enjoy positive effects.

The soils ofBarind and Madhupur Tract areas have very low moisture retention capacity. In winter months (December-January-February) the two areas would face moderate to high drought conditions due to high evapotranspiration rates. The Sal forest ecosystems in these areas would, therefore, suffer due to moisture stress. Further water stress due to increased groundwater demand for irrigation would have compounding effects on the regeneration process of the species in those areas.


Most of the tea gardens are located in Sylhet, north-eastern part of Bangladesh. Generally,

tea grows well within a temperature range of about l8-25°C and a minimum rainfall of

about 1200-1250rnm. Carr (1972) showed that an even distribution of rainfall is more

important for tea plantation than the total amount of rainfall. Since climate change would

cause extreme events and rainfall in the winter months would decrease, therefore, it might

cause a decline in quality of tea plants by affecting surface moisture availability.

5. Impacts on Mangrove Forests

Mangrove ecosystems of Bangladesh are located in the Sundarbans, the south-west parts

of the country bordering India, and in offshore islands of Bhola, Moheshkhali and in

Chokoria of Cox's Bazaar district (Figure-3). The former houses the largest patch of

productive mangrove in the world, constituting more than 95% of the mangroves in the

country. The other mangrove ecosystems are severely degraded due to continued

encroachment, whereas the Chokoria Sundarbans (about 7500 hectares) has been

completely denuded during the past three decades.

FIGURE 3. Location of mangrove forests in Bangladesh

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However, the mangrove forest ecosystems deserve special mention not because they

provide a number of valuable goods and services to the millions of people of Bangladesh,


they are extremely rich in flora and fauna biodiversity. Since the fate of all such animal and plant species living in the forests would depend on the condition of the forests, it is of extreme importance to examine the vulnerability of the forests under climate change scenarios. For simplification the discussion will be limited only to the Sundarbans ecosystem. The following sub-sections are heavily drawn from Ahmed (1998).

5.1. GENERAL FEATURES OF THE SUNDARBANS

The Sundarbans is ideally located in the estuaries of the three mighty rivers: the Ganges, the Brapmaputra and the Meghna. The landscape of the Sundarbans consists of a large number of fluvial and tidal geomorphological features created by the continual deposition of weathered materials carried by the GBM river systems. Mudflats are formed along the estuaries or riverbanks and are subjected to direct wave action, flow and turbulence of the water currents in the river. The lower parts of mudflat remains submerged during all high tides. Backswamps or basins are also found to occur as low lying saucer shaped depressions. These collect rainwater and sediments, the latter being washed away each year during the early monsoon season. Ridges or levees are found to exist due to sediment deposition on the edge of the riverbank. Some levees have inclined slopes on their outer edges, with steep gradients towards the channel side. There are creeks and streamlets that are influenced by tides and maintain inter-connection between rivers and cross channels.

The Sundarbans is influenced by tides that are semi-diurnal. There is a seasonal variation of tidal height ranging between 3.5 to 5.0 metres, while the mean tidal height is about 4.0 metres. Tidal height is also influenced by lunar periods. The mean water level of the rivers changes between wet and dry season due to the onset of monsoon winds and high discharge of freshwater. Thus the water level reaches its peak during the wet season (JulyAugust) and its lowest level during the dry season (December-January).

All areas below the lowest water level are regularly flooded by almost all high tides. Elevations above this level are subjected to flooding during spring tide only and remain exposed during neap tide. Besides tidal variations, the occurrences of monsoon floods and cyclonic surges raise the water levels of the rivers, causing submergence of elevated lands that do not undergo regular inundation. River flow and tidal currents play a vital role in creating the environmental conditions of the estuary.

The soil of the Sundarbans is saline due to tidal interactioas, although the salinity is low compared to soil salinity in other mangrove forests of the world (Karim, 1988). Soil salinity, however, is regulated by a number of other factors including surface runoff and groundwater seepage from adjacent areas, amount and seasonality of rainfall, evaporation, groundwater recharge and depth of impervious subsoil, soil type and topography etc. It is found that, conductivity of subsurface soil is much higher than that of surface soil (Chaffey et al., 1985). Using the salinity scale established by Walter (1971), the forest areas have been divided into three zones based on soil salinity (Karim, 1988).


5.1.1. Oligohaline (or miohaline) Zone The zone is characterised by the soil contammg less than 5 ppt of NaCl salt. The oligohaline zone occupies a small area of the north-eastern part of the forest.

5.1.2. Mesohaline Zone The zone is characterized by NaCl content within the concentration range of 5 to 10 ppt in soil. This zone covers the north-central to south-central part of the forest.

5.1.3. Polyhaline Zone The NaCl content of the soil in this zone is higher than 10 ppt. This zone covers the western portion of the forest.

Figure-4 presents the three zones, based on data of soil salinity in dry season. The boundaries, however, of these zones are not static and their precision remain tentative owing to high variability of salinity conditions within the zones. The general feature of soil salinity is that it increases from east to west. The increasing trend of soil salinity from north to south is not uniform throughout the forest. Soil salinity influences the floral distribution of the forest.

FIGURE 4. Salinity zones in the Sundarbans forest

Bay of Bengal

A forest inventory completed by Chaffey et a/., (1985) reported that the forest had ten forest types and it consisted of eight dominant plants namely sundri (H. fames), gewa (E.


agallocha), passur (X mekongensis), dhundul (X granatum), kankra (B. gymnorhiza), keora (S. apetala), baen (A. officina/is) and goran (C. decandra). It was also reported that H fames- E. agallocha forest type covered the largest area (29.45%) followed by pure H fames (21%).

There is a wide variation of vegetation in the Sundarbans. It varies from multi-storied forest forming closed canopies to scrubby bushes with widely dispersed stunted trees. Moderate to relatively freshwater areas ( oligohaline zone) support the best developed forest. While in the sea front areas (polyhaline zone), the forest consists of poor growth trees and shrubs. The general vegetation types with the dominant species in respect to salinity zones are presented in Table-3.

TABLE 3. The general vegetation types in respect to soil salinity zones

Salinity Land form types zone Oligohaline Mudflat (outer zone)

Mudflat (interior)

Mudflat-ridge (levees)

Backswamps

Mesohaline Mudflat (interior)

Vegetation type/major species

Mixed. P. karka (no! khagra), Nfruticans.

E. agallocha.

Pandanus foetidus (kewa katta).

Stratum-A: H fames (D), S. apetala, A. officina/is.

Starum-B: E. agallocha.

Stratum-C: C. ramiflora (shingra).

P. coarctata, N fruticans, S. apetala, E. agallocha(D).

Mudflat (inclined slope) S. apetala, S. caseolaris, A. officina/is, N fruticans,

Hfomes(D), E. agallocha(D), C. decandra(D) etc.

Polyhaline

Backswamps

Mudflats

Backswamps (at low elevations)

Note: D stands for dominant species. Source: Ahmed, 1998

H fames (D) in association with A. cuculata and B. gymnorhiza as undergrowth.

Upper stratum-S. apetala (D), A. corniculatum with A. ilicifolius as undergrowth.

A, marina (D) in sea fronts with A. corniculatum and S. apetala.

Mixed growth. E. agallocha (D) in upper story and C. decandra as undergrowth. Sparse canopy with degraded quality.

5.2. POSSIBLE IMP ACTS ON THE SUNDARBANS ECOSYSTEM

Examining the possible impacts of climate change it appears that there would be more rainfall in monsoon which would force high incidences of floods in terms of intensity and frequency. Rainfall runoff would provide increased freshwater discharge to all the major distributaries of the Ganges supplying freshwater to the Sundarbans. But increased sea


level would cause backwater effect, thereby delaying the discharge process in the estuary. As a consequence, there would be relatively prolonged inundation in the Sundarbans areas in monsoon months (July-September) and also, increased rate of sedimentation/siltation in the backswamps and creeks inside the forest area.

A significantly different environmental condition might be expected in winter months. There would be significant lowering of freshwater discharge in the rivers coupled with high rate of evaporation. Just to offset increased evaporation, the rate of surface and ground water abstraction for irrigation in the upstream areas would be increased resulting into lesser amounts of freshwater discharge in rivers coming on to the Sundarbans. As a consequence, it is highly possible that the rate of salinity intrusion into the forest would increase.

The impact on salinity intrusion would be compounded with climate change induced increased incidences of cyclonic storm surges in the Bay .. Storm surges would inundate high levees and backswamps that do not get submerged with saline water and thereby would be affected by salinity.

The biota of the Sundarbans forest are highly influenced by salinity regimes of surface and groundwater systems and more significantly, of soil. As it has been described above, salinity of a particular forest area defines which type of vegetation is expected to dominate. Natural regeneration of vegetation and forest succession also depends on salinity regime (Karim, 1994 and Siddiqi, 1994). Since soil salinity inside the forest would significantly change in respect to the present salinity, it is highly likely that increased salinity would have discemable adverse impacts on forest regeneration and succession. This would in tum affect the long-term sustainability of the ecosystem. Furthermore, the highly dense human settlements just outside the forest area would restrict the species migration to less saline areas. A combination of the two effects would therefore threaten the very existence of the ecosystem.

Even if the forest would manage to survive such threats, but due to increased salinity the present species composition will certainly change. It has been observed in the Indian side of the forest that, due to gradual increase in salinity the freshwater loving sundri (H. fomes) trees disappeared while the area has been covered by shrubs and saline tolerant grasses (Chaudhuri and Choudhury, 1994). It is also reported that the remaining sundri trees, those survived in the less saline areas, shrunk in size. Similar phenomenon would occur due to increased salinity in the Bangladesh's side of the forest under climate change conditions.

Ahmed (1998) reported that the ex1stmg oligohaline zone would be completely transformed into mesohaline zone. As a result areas with best quality standing timber predominated by long Avicennia officinalis and H. fomes would be replaced by inferior quality tree species, predominated by H. fomes - E. agallocha and Ceriops - Excoercaria

forest types. In a similar fashion, a significant part of the existing mesohaline zone, especially the south-western parts of the Sibsa river up to 22°00 N would be transformed


into polyhaline (saline areas with NaCl content >lOppt in soil) zone. As a result, grasses, thorny herbs/shrubs and trees of poor quality would dominate and gradually replace woody tree species. Under such conditions vegetation canopy would become sparse and plant height would be reduced significantly (Ahmed, 1998).

With a change in species composition the productivity of the forest would be severely constrained. Chaffey et al. (1985) demonstrated that, total merchantable wood volume per unit area of forest land decline with increasing salinity of soil and river water. Disappearance of oligohaline areas combined with decreasing mesohaline areas would result into over 50% loss of merchantable wood from the Sundarbans. Increase in salinity in the Indian side of the forest would have compounding effect to the existing poor productivity of the forest.

The salinity would not be a problem in monsoon. Because there would be enhanced flushing with freshwater and the surface water salinity would be pushed back towards the sea. But change in water level due to higher discharge and rainfall runoff combined with backwater effect due to sea level rise would cause drainage congestion in the estuaries. The latter would result into increased rate of sedimentation/siltation in the submerged areas. As a consequence the backswamps of the Sundarbans would gradually be filled up. This will also cause changes in regeneration capacity of the species as well as productivity in the long run. Moreover, the low-lying mudflats would be more frequently submerged which could slow down forest succession process.

5.3. PROBABLE ADAPTATION ALTERNATIVES

Though the evaluation of the adaptation alternatives will be sought later on, some indications are given at this stage of the study which are as follows:

a) To mitigate loss of forest land due to sea level rise, the process of land accretion may be accelerated by considering appropriate interventions.

b) To prevent further intrusion of salinity in the southern region of the country, it may be necessary to increase the freshwater supply in the Mathabhanga and Gorai-Madlumati river systems. This would require implementation of proposed Ganges barrage, which would, among other things, allow more freshwater supply in the south-west region including the Sundarbans.

6. Conclusions

Impacts of climate change will increase moisture stress in winter months, enhance and prolong floods in monsoon, produce higher salinity in the coastal areas and have possible higher incidences of tropical cyclones and storm surges affecting the coastal areas. Increased moisture stress in the Barind and Madhupur Tract areas would cause accelerated degradation of the forests. Prolonged floods would affect tree species that do not prefer


water-logged conditions. Enhanced salinity intrusion would limit afforestation potential in the coastal villages. Cyclonic storm surges would cause wide-scale damage to most forest species in the affected areas as it has already been observed following the cyclonic storms of 1991, 1994 and 1997.

FIGURE 5. Forest succession in the three salinity zones in respect to land elevation and tidal height

~~~ ~ ·o-r-

" \)~'if c,l/;$s\ C. decandra

" sv.G E. agallocha

#'<'Lo-r- " t MHWS ' <?i\ c,e?s\ " E. agallocha v.c;

' s C. decandra

" l ' t ' H. fomes

c~l -..= ~

'Cij ' .............................. = -; MXHWD Hf-~ J H~ J ........ E. agallocha "'0 E. agtlocha B. gytorhiza

........ ....._ C. decandra ~ ........ ........ t 0 - H. fomes H. fomes E.agallocha = A. cuculata A. cuculata H. fomes .9 - C. ramiflora C. ramiflora C. decandra ~ t t t "'Cij ~

.!3 H. fomes H. fomes E. agallocha E. agallocha E. agallocha C. decandra

= t t H. fomes .9

t -~ LHWS A. officinalis A. officinalis ~ ell H. fomes H. fomes ~ E. agallocha E. agallocha "'0 t =

i i ~ ~ Nypa Nypa S. apetala

_jL _jL A. marina

S. apetala S. apetala S. apetala A. marina

t t t Phragmites karka Porteresia coarctata Porteresia coarctata

MHWN Typha elephantina P. karka

OLIGOHALINE MESOHALINE POLYHALINE

Salinity Notes: MHWS =Mean high water of spring tides; MHXWD =Maximum high water of spring tides during dry season; LHWS =Low high water of spring tide during dry season; and MHWN =Mean high water of neap tides.

Source: Karim, 1994


The most significant impact, however, would be observed in the Sundarbans forest. A possible shift in salinity zones would force ecological transformation and the freshwater loving woody tree species would be gradually replaced by bushy shrubs/herbs, grasses and non-woody plants. Furthermore, the species migration to freshwater zones would be limited due to human pressure coupled with enhanced withdrawal of surface water for irrigation in the upstream. Such a transformation would, perhaps, lead to a ecological disaster. Many of the wild animals including the Bengal Tiger would find it difficult to adjust to such dramatic changes.

The Government of the People's Republic of Bangladesh has recently adopted the Forestry Master Plan. The Plan, however, failed to address the issue of climate change and its impacts on forestry sector in totality. This study provides a holistic view of the problem. A more in-depth study on the major forest species will provide valuable insight to take adaptation measures against climate change related problems. Once the adaptation alternatives with complete analyses are made available it would then be possible to find ways to reduce vulnerability of the forestry sector.

References

Ahmed, A.U., 1998. Ecological Security in a Warmer World: The Case of the Sundarbans. BUP Monograph. Bangladesh Unnayan Parishad, Dhaka, Bangladesh.

Ahmed, A.U. and Alarn, M., 1998. Development of Climate Change Scenarios with General Circulation Models. In Vulnerability and Adaptation to Climate Change for Bangladesh. S. Huq, Z. Karim, M. Asaduzzaman and F. Mahtab (Eds.), Kluwer Academic Publishers, Dordrecht, The Netherlands. pp. 13-20.

Alarn, M., Nishat, A. and Siddiqui, S., 1998. Vulnerability of Water Resources to Climate Change with Special Reference to Inundation, In Vulnerability and Adaptation to Climate Change for Bangladesh. S. Huq, Z. Karim, M. Asaduzzaman and F. Mahtab (Eds.), Kluwer Academic Publishers, Dordrecht, The Netherlands. pp. 21-38.

BCASIRA/Approtech, 1994. Vulnerability of Bangladesh to Climate Change and Sea Level Rise: Concepts and Tools for Calculating Risk in Integrated Coastal Zone Management. Bangladesh Centre for Advanced Studies, Resource Analysis, Delft, The Netherlands and Approtech Consultants Ltd., Dhaka, 1994.

Carr, M.K.V., 1972. The Climatic Requirements of the Tea Plant: A Review. Experiment Agriculture, 8, 1-14.

Chaffey, D.R, Miller, F.R., and Sandom, J.H., 1985. A Forest Inventory of the Sundarbans, Bangladesh. Main report. Overseas Development Administration, England. 196 pp.

Chaudhuri, A.B. and Choudhury, A., 1994. Mangroves of the Sundarbans, Volume One: India. IUCN- The World Conservation Union, Bangkok, Thailand.

Forestry Master Plan, 1995. Asian Development Bank (TA No. 1355-BAN). Ministry of Environment and Forest, Government of the People's Republic of Bangladesh.


Jordan, C.F., 1985. Nutrient Cycling in Tropical Forest Ecosystem: Principals and Their Applications in Management and Conservation. Wiley, Chichester a.o., 190pp.

Karim, A., 1994. Vegetation, In Mangroves of the Sundarbans: Volume Two: Bangladesh. Hussain, Z and Acharya, G. (Eds.) 1994.1UCN- The World Conservation Union.

Karim, A., 1988. Environmental factors and the distribution of mangroves in Sundarbans with special reference to Heritierafomes. Buch.-Ham. Ph.D. thesis (unpubl.), University of Calcutta.

Korner, C., 1993. C01 fertilization: the great unceratinty in future vegetation development. In Vegetation Dynamics and Global Change. A.M. Solomon and H.H. Shugart (Eds.). Chapman & Hall, New York and London, UK, pp. 53-70.

Kirschbaum, M.U.F., 1995. The temperature dependence of soil organic matter decomposition and the effect of global warming on soil organic carbon storage. Soil Biology and Biochemistry, 27, 753-760.

Kirschbaum, M.U.F. and Fischlin, A. (Eds.), 1996. Climate Change Impacts on Forests. In Climate Change 1995: Impacts, Adaptations and Mitigation of Climate Change: Scientific-Technical Analyses. R.T. Watson, M.C. Zinyowera and R.H. Moss (Eds.). Cambridge University Press.

Leuschner, W.A. and Khaleque, K., 1987. Homestead agro-forestry in Bangladesh. Agroforestry SystemsJ. 5(2): 139-152.

Melillo, J.M.; McGuire, A.D., Kicklighter, D.W., Moore III, B., Vorosmarty, C.J., and Schloss, A.L., 1993. Global climate change and terrestrial net primary production. Nature 363, 234-240.

Raich, J.W., Rastetter, E.B., Melillo, J.M., Kicklighter, A.D., Steudler, P.A., Peterson, B.J., Grace, A.L., Moore III, B., Vorosmarty, C.J., 1991. Potential net primary production in South America: application of a global model. Ecological Applications, 1(4), 399-429.

Siddiqi, N.A. 1994. Natural Regeneration, In Mangroves of the Sundarbans: Volume Two: Bangladesh. Z. Hussain, and G. Acharya, (Eds.) 1994. IUCN- The World Conservation Union.

Walter, H., 1971. Ecology of Tropical and Sub-Tropical Vegetation. New York. Van Nostrand. 539 pp.

Whitmore, T.C., 1984. Tropical Rain Forests of the Far East. Clarendon Press, Oxford, UK, 2"d Ed.,352pp.

Wullschleger, S.D., Post, W.M., and King, A.W., 1995. On the potential for a C02 fertilization effect in forests: estimates of the biotic growth factor, based on 58 controlled-exposure studies. In Biospheric Feedbacks in the Global Climate System- Will the Warming Feed the Warming? G.M. Woodwell and F.T. Mackenzie (Eds.). Oxford University Press, New York, and Oxford, UK, pp. 85-107.

FISH RESOURCES VULNERABILITY AND ADAPTATION TO CLIMATE CHANGE IN BANGLADESH

M. YOUSSOUF ALI Advisor Fisheries Division Bangladesh Centre for Advanced Studies (BCAS)

ABSTRACT

Fish and Fisheries have been playing a very significant role in nutrition, culture and economy of Bangladesh from time immemorial. Currently, about 80 per cent of the animal protein intake in the daily diet of the people comes from fish. The fisheries sector, it is estimated, contributes 3.5 per cent of the GDP of Bangladesh. From habitat point of view, three principal habitat forms exist from which fish are harvested. These are pure freshwater habitats in the rivers and their floodplains. These water bodies are inhabited by 260 species of fin fish, 25 species of prawn and 25 species of turtles. In addition, 11 exotic species of fin fish have been introduced for the purpose of aquaculture. In portions of the freshwater rivers near their confluence with the sea i.e., Bay of Bengal, the water changes from fresh to saline conditions, with a wide range of salinity gradient both spatially and temporally. These tidal parts of the rivers constitute the estuaries with brackish water conditions. Many freshwater species of fish and prawn visit the estuaries and brackish water habitats at different stages of their life cycle. Similarly, post-larvae of many coastal and marine prawns come to the brackish water habitat to feed and grow into adults. In the Upper Bay of Bengal bordering Bangladesh, 4 7 5 species of fin fish are known to occur of which about 65 are of commercial importance. The marine waters also contain about 38 species of marine prawn. In Bangladesh very little or no work on the physiology and ecology of indigenous species of fin fish or prawn has been done. As a result, it is difficult to state or predict likely effects of climate change on different fish/prawn populations and the fisheries based on them. However, some likely effects of climate change on fish habitats are presented in this article.

113

114 M. YOUSSOUF ALI

1. Introduction

Bangladesh is located in the delta of the world's three major river systems having the reputation of being very rich in inland openwater capture fisheries production. Inland water fish used to be caught practically by most of the people, particularly those living in the rural areas. A large number of fish and prawn could be captured by men, women, and children at their door steps during the monsoon, when all the low-lying areas of the country remained under floodwater. According to the World Bank (1989), in the freshwater fish production per unit area, Bangladesh is the world leader with 4,016 kg/km2

and per capita production is about 5.5 kg.

In the inland openwater system of Bangladesh, there exist 260 species of fm fish belonging to 55 families (Rahman, 1989), about 63 species ofpalaemonid and penaeid prawn and several species of crab belonging to the family Potamonidae also occur. Besides the above, 31 species of turtles and tortoises are found of which 24 live in freshwater (Sarker and Sarker, 1988).

Fish and fisheries have been playing a very significant role in the nutrition, culture and economy of Bangladesh from time immemorial. According to a local adage, 'MacheBhate Bangali', i.e. a Bengali body is made up of fish and rice. This adage reflects the role of fish in the food habit, diet and nutrition of the people of Bangladesh. Currently, about 80 per cent of the animal protein intake in the daily diet of the people comes from fish (Karim and Ahsan, 1989).

The fisheries sector, it is estimated, contributes about 3.5 per cent of the GDP of Bangladesh. Within the Agriculture sector, fisheries sector accounted for 6.9 per cent of the gross value added (Karim and Ahsan 1989). Fisheries sector provides full time employment to an estimated 2.0 million people.

In Bangladesh, there is no study as yet on assessment of climate change induced vulnerability of the fisheries sub-sector, particularly on the physiology and ecology of indigenous species of fm fish or prawn. Without such studies, it is very difficult to state or predict the likely effects of climate change on different fish/prawn populations and the fisheries based on them.

2. Primary Fish Habitat

From habitat points of view, three principal habitat forms exist from which fish are harvested. These are i) major rivers and their floodplains, ii) heels, and iii) estuaries. Among them area under rivers and their floodplains and estuaries are 90 and 8 per cent of inland openwater, respectively. Rivers and their floodplains and beefs are the main habitat for major carps and catfishes. Details are presented below.

FISHERIES SECTOR ASSESSMENT

2.1. RIVERS AND THEIR FLOODPLAINS

115

The world's major river systems flowing through Bangladesh are the Ganges, the Brahmaputra, and the Meghna. All major rivers have numbers of tributaries and distributaries. Rashid ( 1991) estimated that the total length of rivers, streams, and canals together cover more than 24,000 km. In an average year, 870 million acre feet (mat) of water flow into the country from India. Another 203 maf accumulate within the country through local rainfalls. Out of this total amount of water, about 953 maf flow to the sea of which 914 maf are through the Ganges-Brahmaputra-Meghna river system and 39 maf through the rivers of the Chittagong sub-region.

All these rivers and their tributaries, and distributaries overflow their banks and flood extensive areas of the low-lying lands during the monsoon from May to October. According to Welcomme (1979), Bangladesh has 9,300,000 ha offloodlands, including 2,834,000 ha of paddy fields, remain inundated for three to four months of the year. Bangladesh has also an estimated 1,400,000 ha of permanent open inland-waters. According to the Master Plan Organisation (MPO, 1987 a, b) the total estimated area of floodplains was 6,300,723 ha in the past, of which 814,114 ha had been dried up through flood protection measures, leaving a balance of 5,486,609 ha upto the end of June 1985. Up to the end of June 1990, another 3.36 million ha of floodplains were protected from flooding through the construction of 7,024 km of embankments, 3,017 km of drainage channels, 6,884 hydraulic structures, 1,064 river closures, and 3,888 bridges and culverts (MPO, 1990).

Of the areas of floodplains, the most significant area is the large central depression (Sylhet depression) in the north-east region. According to the Flood Action Plan (F AP-6, 1993a, b), the topography of the north-east region consists of a large central depression flanked by floodplains, then gently sloping piedmont, bordered distally by piedmont hills extending into India. The minimal elevation is 1.5 m above the sea level in the Sylhet depression and the maximum is 30m in the piedmont hills.

For the purpose of fisheries production assessment, F3 and F4 land type categories of MPO, both being greater than 180 em of flooding, are lumped together. Area under different land type categories are given in Alam eta!., 1998.

2.2. BEELS

Beefs are deepest region of depressions within the floodplains which retain water round the year or greater part of the year. The saucer shaped basins of floodplains in northeast region are termed as haor. The number of beefs in the north-east region has been reported to be between 3,440 (covering 58,500 ha with a mean size of 7 ha) and 6,149 (covering 63,500 ha with a mean size of 10 ha) (Bemacsek eta!., 1992). About 58% of the beefs in the north-east region are permanent and the remainder is seasonal.

116 M. YOUSSOUF ALI

In the other regions of the country, beefs are seen almost all over. All low-lying areas inundated and submerged for a number of months, usually from June to September and becoming dry in the dry season, are also termed as beefs in other regions of the country.

In the north-west region, Dinajpur district has no big beefs. In Rajshahi, Chapai Nawabganj, Naogaon and Natore districts of the region, beefs at one time were plentiful. The most reputed of the beefs in this region is the Chalan beef spreading over the districts of Naogaon, Natore, Pabna, Sirajganj, and Bogra. The Chalan beef once consisted of a chain of beefs interconnected by channels forming a beef system which used to become one continuous sheet of water in the rainy season. Some of the beefs in the Chalan beef complex are Haiti, Piprul, Purbamadhnagar, Sonapatila, Ghugudaha, and Kuralia. The Chalan beef complex, according to Rashid (1991), was a sort of a lake covering an area of 109,000 ha but, by 1909, the area under water was reduced to only 8,500 ha. The other beefs in Rajshahi and Naogaon districts are Hi1na, Kosba, Uthrail, Manda, Shona, Baghashimli, and Beef Mansur. In the past, Chapai Nawabganj district used to have a large number of beefs, but over the years most of these have dried up due to both natural processes and human interventions.

In the central region of the country, a few well-known beefs, such as Arial bee! in the Munshiganj district and Beef Belai in the Dhaka district once existed. Because of expansion of human settlements and other human interventions, these beefs have lost their importance from the point of natural fish habitats and fish production. In the districts of Faridpur, Madaripur, Rajbari, and Gopalganj in the south-central region, large tracts of low-lying floodplains are present and are termed as beefs. Some of these are Chanda bee!, Boro beef, Mollar beef, Tungipara beef, Kendua bee!, and Bee! Baghia.

In the south and south-west regions beefs also are seen. For example, Chapaigachi heel in Kushtia district, Garalia bee! and Panjiapatra beef in Jessore district, Chenchuri heel, Ponamara beef in Narail district and Bamal beef, Selimpur beef, Kola beef, Ketla heel, and Beef Dakatia, in Khulna district. In the south-eastern region, including Chittagong and Noakhali districts, beef- like depressions are not many.

Another form of waterbodies found in Jessore and Jhenidah districts and their adjacent areas in Kushtia district are in the south-west region locally known as baors. The baors (oxbow lakes) are the old meandering bends of rivers which got cut off from the main stream. The baors are, strictly speaking, not parts of the openwater system.

2.3. ESTUARIES

All the major rivers meet the Bay of Bengal in the south of the country. Near the confluence of the sea and the rivers, freshwater is replaced by a mix of saltwater and freshwater producing brackish water, and forming a distinct estuarine zone. A wide range of salinity gradients are encountered in the rivers up to a considerable distance upstream from the shore line of the Bay of Bengal.

FISHERIES SECTOR ASSESSMENT 117

Along the coast in the south, an estimated 2.5 million ha of low-lying lands are subject to tidal inundation. In the past, these areas used to provide, during high tides, temporary nursery and grazing grounds for larvae, fry, and juveniles of different marine fishes and shrimps (Tsai et al., 1978).

In the south-western region, the principal ecological feature is the presence of the largest mangrove forest in the world, known as the Sundarbans. The entire Sundarbans forest is a reserved forest zone and is managed by the Forest Department. It is crisscrossed by an intricate network of large and small rivers, canals and creeks. The total water area is estimated to be 175,600 ha (Ali, 1991b). The whole forest area is inundated by tidal water twice every day. Water is estuarine with a wide range of salinities. Rivers in the Sundarbans forests at their northern-ends receive freshwater inflow from the upper portions of the rivers, while in the south they meet the saline waters of the Bay of Bengal. The water in the Sundarbans is rich in detritus and nutrients, supporting a large variety of both cartilaginous and bony fishes, shrimps, crabs etc.

Areas under different components of the open inland-water system were computed by the Space Research and Remote Sensing Organisation (SPARRSO) for the Department of Fisheries (DOF), Bangladesh (DOF, 1990) and the MPO (MPO, 1986, 1987a). Table-1 shows the summarised version made by Ali (1991a).

TABLE 1. Areas under different types of inland open waters areas

Type Ganges River PadmaRiver Brahmaputra-Jamuna Upper Meghna Lower Meghna Other rivers and canals (khals) Sub-total for rivers Estuarine areas Total (rivers and estuaries) Bee/ and haors Floodplains Kaptai Lake

GRAND TOTAL Source: Ali, 199Ja

3. Fish Species Diversity

Area(ha) 27,165 42,325 73,666 33,592 40,407

262,580 479,735 551,828

l,Q31 ,563 114,161

5,486,609

68,8ooc 6,701,133

References

MPO, 1986 MPO, 1986

DOF, 1986 MPO, 1987a DOF, 1986

In Bangladesh, all the 260 species of fm fish are of importance from economic, social and nutritional points of view. They may be broadly categorised into species that attain large-sizes and species that do not grow to large sizes. The large-sized species

118 M. YOUSSOUF ALI

undertake long migration in the rivers for breeding. The small-sized fishes undertake migration over shorter distances or reside in floodplains, beels, and canals.

3.1. INLANDWATERS

3.1.1. Large-Sized Fishes Fish species that attain large sizes are locally termed as Boromaach, such as major carps belonging to the family Cyprinidae, and large catfishes belonging to the families Siluridae, Schilbeidae, Bagridae, and Sisordae under the suborder Siluroidei. The important species of catfishes are boaal (Wallago attu), silond (Silondia silondia), pangas (Pangasius pangasius), aire (Mystus aor), baghaire (Bagarius bagarius), and rita (Rita rita). The most important commercial fishery for the large-sized fish is the ilish (Hi/sa ilisha), belonging to the family Clupeidae. Hilsa or ilish is a marine fish but ascends the freshwater portion of the rivers for spawning. During their upstream migration in the rivers, they are caught in huge numbers. The other large-sized fishes are chital (Notopterus chitala) belonging to the family Notopteridae and shol and gazar belonging to the family Channidae.

3.1.2. Small-Sized Fishes Fish species that do not attain large sizes are termed as chhotomaach. The majority of fin fishes in the inland-waters belong to this category. They are important from the viewpoint of providing nutrition and subsistent and supplemental income to the vast majority of the rural people including the poorest of the poor, the landless and the destitutes. The small-sized fishes include minor carps (raig, bata, kalabata, angrot, punti, sarpunti, chela, darkina, jaya, morar, along, bhol, koksa, patharchata, barali, chapchela, anju, chebli, nepati, mola, lohasura, jarua, ghonia, etc.) belonging to the family Cyprinidae; techokho and kanpona belonging to the family Cyprinidontidae; kakila (gars) belonging to the family Belonidae; half-beaks belonging to the family Hemirhampidae; taki, cheng, tila shol, etc. belonging to the family Channidae; balitora and titari belonging to the family Psilorhynchidae; bilturi, koirea, panga, rani, lohachata, gunturn, puiya, etc. (loaches) belonging to the family Cobitidae; magur (family Claridae); pabda, modhupabda and pabo pabda belonging to the family Siluridae; shingi (family Heteropneustidae); chaga (family Chacidae); kajuli, baspata, batashi, bacha, ghaura, etc. of the family Siluridae; several species of tengra, guzi aire, etc. belonging to the family Schilbeidae; several species of the family Sisoridae, such as gang tengra; several species belonging to the family Tachysuridae; pholi (Family Notopteridae); anchovies, such as phasa (family Engraulidae); chapila, (Gudusia chapra), kechki (Carica soborna), goni chapila (Gonialosa manminna), etc. of the family Clupeidae; tara bairn (Macrognathus aculeatus), bairn or sal bairn (Mastacembelus armatus), pankal (Mastacembelus pancalus) belonging to the family Mastacembelidae; kholisha, neftani and koi (family Anabantidae), bele (Glossogabius giuris) and several other members of the family Gobiedae; meni or bheda (Nandus nandus) of the family Nandidae; chanda (Chanda nama), ranga-chanda (Chanda ranga), etc. belonging to the family Centropomidae, etc.

FISHERIES SECTOR ASSESSMENT

3.2. MARINE WATERS OF THE UPPER BAY

119

In the upper Bay of Bengal bordering Bangladesh, 4 7 5 species of fin fish are known to occur, of which about 65 species are commercially important. In the upper Bay of Bengal also occur 38 species of marine prawn (Ali, 1992). Of the fish species, the most important ones are Hilsa, an anadromous species which contributes about 38 per cent of the total fish harvest of Bangladesh. Fish species such as Bombay duck (Harpodon nehereus), Indian Salmon (Polydactylus indicus), Pomfrerts (Pampus argenteus; Pampus chinensis), etc. are also harvested. Of the marine prawns, the important one is tiger prawn (Penaeus monodon).

Estuarine fishes are parshe (Mugil parsia), khorsul (M. corsula), bhangon bata (M. tade) belonging to the family Mugilidae; bhetki (Lates calcarifer) belonging to Centropomidae, and number of species under the families Toxotidae, Leiognathidae, Sciaenidae, Scatophagidae, Taeniodidae and Gobiidae. Some of these estuarine fishes come upstream into freshwater habitats.

Occurrence of a cartilaginous fish, shankosh or Gangetic stingray (Himantura jluviatilis) in the Kushiyara River in Sylhet was reported (FAP-6, 1993a). This species has also been reported from other rivers in the country. Most of the smaller sized fishes do not undertake a long distance breeding migration. They move short distances laterally into shallower water areas for breeding. Many of them live in inundated floodplains, beefs and marshes, and breed in the monsoon season.

3.3. PRAWNS

Besides fin fishes, the inland-waters of Bangladesh support a large number of prawns. Ali (1992) lists 63 species of prawns. Of them 14 species belong to the genus Macrobrachium, 5 species belong to genus Palaeomon, 1 species to genus Leander and 1 species to genus Leandrites and 2 species to genus Leptocarpus. All belong to the family Palaemonidae living in freshwater and brackish water habitats and two species of genus Caridina belonging to the family Alpheidae live completely in freshwater habitat. Two species of the genus Alphaeus of family Alpheidae, live in brackish and sea water. Under the family Penaeidae, 8 belong to the genus Penaeus, 6 to genus Metapenaeus, 6 to genus Parapenaeopsis, 4 to genus Solenocera, 1 to genus Trachypenaeus and 1 to genus Metapenaeopsis. All of them inhabit the brackish and sea water. Another family of marine prawn is Pandalidae with two species of the genus Heterocarpus and 1 species of the genus Plesonika. Two species of the genus Hippolysmata and 1 species of the genus Latreustes, belonging to the family Hippolytidae also occur in the brackish and sea water. Three species of the genus Acetes under the family Sergestidae are available in the brackish water along the coast of Bangladesh.

120 M. YOUSSOUF ALI

All the species belonging to the genus Macrobrachium reside in freshwater habitats in rivers, streams, canals, floodplains, and beels. Many of them undertake long downstream migration to reach estuarine waters for breeding. According to Ali ( 1992), Macrobrachium rosenbergii (golda chingree ), M. malcolmsonii ( chatka chingree ), M. villosimanus (dimua chingree), and M. rude (goda icha) visit the estuarine areas where they breed and their larvae grow for about 30 - 40 days. Thereafter, the juveniles undertake a return migration to the freshwater portion of the rivers, floodplains and beets. The other species such as Macrobrachium lamerrei, M. dyanus, two species of caridina, Palaemon (Nemotopalaemon) tenupies, and Leander (exopalaemon) styliferus, are small-sized prawns and are collectively called goora icha or kucho chingree in Bengali. Of the freshwater prawns, golda chingree is of high commercial value as they attain large size (often two or three individuals/kg) and retch high prices. This prawn also has demand for export. Ali (1992) mentions that the following prawns have commercial value: Macrobrachium rosenbergii, M. malcolmsonii, M villosimanus, M. lamarrei, M. rude, Penaeus monodon, P. indicus, Metapenaeus monoceros, M. dobsonii, and M. brevicornis.

Golda chingree used to be most abundant in the Lower Meghna River and its adjacent floodplains in the Chandpur and Comilla districts around the Dakatia River and Dhonagoda River, as well as near Daudkandi around the confluence of the lower Meghna and Gumti rivers. Recently this giant prawn in these waterbodies have disappeared or have become greatly reduced due to erection of embankments around the floodplains under flood control, drainage and irrigation projects (Ali, 1994b).

3.4. EXOTIC SPECIES OF FISHES

In addition to the indigenous 260 species of fish, 13 exotic species of fish have so far been introduced into Bangladesh (Rahman, 1985). They are two species of cichlids, 7 species of cyprinids (silver carp, grass carp, bighead carp, black carp, 2 strains of common carp, and one barb species), 1 species of clarid and 1 species of large catfish, Pangasius. Their introduction was not preceded by any study with regard to their desirability in relation to the indigenous fishes. Of the introduced species, two species of Tilapia and two strains of common carp seem to have established themselves in the inland openwaters of the country.

4. Description of Main Fisheries Likely to be Affected by Climate Change

In Bangladesh very little or no work on the physiology and ecology of indigenous species of fm fish or prawn has been done. As a result, it is difficult to state or predict likely effects of climate change on different fish/prawn populations and the fisheries based on them. However, some speculations are presented below.


4.1. MARINE AND ESTUARINE CAPTURE FISHERIES

Climate change and consequent sea level rise is likely to affect the water temperature and salinity regimes in the upper Bay of Bengal. Enhanced water temperature may likely affect the reproductive physiology of many of the marine fishes. Increased water temperature is likely to advance the sexual maturation process and timing of spawning of the adults of Hi/sa ilisha populations. This may upset the timings of their spawning migration into the freshwater rivers and estuarine components. This may alter the abundance of Hilsa populations in the fishing grounds in the estuaries and in the freshwater rivers. Other important fisheries are based on the populations of Bombayduck (Harpodon nehereus), Pomfret (Pampus chinensis), and Pampus argenteus and Indian Salmon or Lakhua (Polydactylus indicus). These are all very popular as food fish and occur both in the Bay of Bengal and in the estuaries. This wide range of habitat adaptation of these fishes will likely allow them to adapt themselves to changed salinity conditions. Increased temperature may also bring about changes in their reproductive physiology and season of spawning.

4.2. FRESHWATER CAPTURE FISHERIES

Sea level rise will, in all likelihood, bring about a reduction in the freshwater habitat conditions particularly in the rivers. In the event of such a situation, production of freshwater fishes such as cyprinids, anabantids, channidae, and many others which cannot tolerate any level of salinity in the water, is likely to suffer.

Climate change in Bangladesh will likely lead to increased precipitation, increased frequency of floods and increased water flow to and through the tidal rivers, streams and creeks. This increased upper riparian freshwater flow into the estuaries and coastal areas will alter water salinity gradients of the estuaries and brackish water regions of Bangladesh. Such alterations may make the habitat conditions for various shrimps and fish inhospitable and inaccessible. These will likely eliminate of the affected fish or prawn in years of very low water salinity.

4.3. FRESHWATERPONDCULTUREOFFISHES

Pond culture of indigenous major carps (cyprnids) such as Rohu, Catla, Mrigal and Kalboush and exotic carps such as silver carp is practised extensively in the coastal districts of Cox's Bazar, Chittagong, Noakhali, Feni, Lakshimpur, Bhola, Barisal, Jhalokati, Patuakhali, Borguna, Pirojpur, Bagerhat, Khulna and Satkhira. During the year 1995-96 (July, 95 to June 96), a total production of 105.5 thousand metric tons of major and exotic carps were obtained from freshwater ponds of the aforesaid districts. In the event of sea level rise, these ponds are likely to be submerged under sea water which will lead to the total loss of this major carp production. However, this production can be sustained if submersion can be prevented by constructing ·embankment with appropriate height.

122 M. YOUSSOUF ALI

4.4. BRACKISH WATER SHRIMP FARMING IN THE COASTAL DISTRlCTS

The rivers, canals and creeks in the south-west and south-east regions of Bangladesh are tidally influenced and remain so round the year. The salinity level in the waters of these rivers, creeks and canals increases during the dry months from December to April when post-larvae and juveniles of marine shrimps such as Tiger shrimp (Penaeus monodon), Brown shrimp (Metapenneus monoceros, M. brevicomis), etc. travel from the deep sea into the brackish water rivers, creeks and canals. During their sojourn in the brackish water rivers and canals, they are captured and reared in brackish water ponds and enclosures (ghers) in the south western and south eastern districts.

In view of the world wide demand for brackish water shrimp, this form of shrimp farming has become popular and such farming is increasing. Table-2 presents the year wise figure of shrimp farm areas and shrimp production. From this table, it will be seen that brackish water shrimp production is increasing steadily. The production in 1984-96 was 27,595 mt and this increased to 68,349 mt in 1995-96. This farm produced shrimps are mostly exported to earn foreign exchange. In Table-3, aunual quantity of shrimp exported and income earned from export are shown for the years from 1989-90 to 1995-96. It is seen that earnings from shrimp export are also increasing. In the recent years, export of shrimp has become a major source of foreign exchange earning of Bangladesh.

It is apprehended that once the sea level rises, all these shrimp farm will go under the sea. Consequently, such a lucrative shrimp farming practice will disappear, making the country lose the foreign exchange earning for good.

TABLE 2. Brackish water Shrimp farm areas in the coastal districts of Bangladesh and total production of shrimp from the farms

Years 1989-90 1990-91 1991-92 1992-93 1993-94 1994-95 1995-96

( 1) Brackish water shrimp 108,280 108,280 108,280 108,280 137,996 137,996 137,996 farm areas (hectare) (2) Total production of 27,505 28,431 30,147 33,773 39,447 47,831 68,349 shrimp (metric tonnes)

Source: Fisheries Resources Survey System (FRSS). Department of Fisheries, Bangladesh

TABLE3. Quantity of shrimp exported and income earned in different year

Years 1989-90 1990-91 1991-92 1992-93 1993-94 1994-95 1995-96

Quantity of shrimp 17,505 17,985 16,730 19,224 22,054 26,277 25,225 exported (metric tonnes) Income earned (in 4,143 4,512 4,557 6,040 7,877 10,456 11,064 Million Taka)

Source: Export Promotion Bureau, Government of the People's Republic of Bangladesh.


5. Probable Adaptation Alternatives

Since brackish water shrimp farm activities and the occurrence of mangrove plantations such as the Sundarbans, are interlinked, monitoring of the formation of new shoreline areas and formation of new mangrove plants should be undertaken and regeneration of mangroves need be encouraged.

The zones appropriate for growing shrimp on the coastal belt need to be delineated and monitored so that any shifts in saline zones can be detected well ahead of time and appropriate adjustments in the shrimp growing areas be made.

With respect to the riverine fish species specially Hilsa it will be necessary to obtain better data on the salinity levels and tolerances as well as its preferred temperature profile of this species in order to predict with any level of certainty what-the impacts of climate change and accelerated sea level rise may be.

References

Ali, M.Y., 1991 a. Towards sustainable development: fisheries resource of Bangladesh. Ministry of Environment and Forest and National Conservation Strategy Secretariat, Bangladesh Agricultural Research Council, Farmgate, Dhaka. May 1991. pp. 96.

Ali, M.Y., 1991b. Fisheries management-Section 5 in the report of the Sunderbans of Bangladesh, World Bank Forestry Project prepared by Asian Wetland Bureau, Institute of Advanced Studies, Univesity of Malaya, Lembah Pantai 59100, Kualampur, Malaysia. 1991. pp. I 09-131.

Ali, M.Y., 1994. Report on the study of the fisheries situation under the socio-environmental assessment of Meghna-Dhanagoda Irrigation Project. Bangladesh Centre for Advanced Studies (BCAS) and Bangladesh Engineering and Technological Services (BETS), Dhaka. August 1994, pp. 51.

Ali, S., 1992. Chingree: Bangladesher Chingree Utpadon 0 Chash (in Bengali)" (Cultivation and production of prawn in Bangladesh). Bangia Academy, Dhaka, pp. 98.

Bernacsek, G. M., Nandi, S. and Paul, N.C., 1992. Draft thematic study: fisheries in the North East Region of Bangladesh. North East Regional Water Management Project (FAP 6). Shawinigan Lavalin (1991) Inc., North West Hydraulic Consultants in association with Egineering and Planning Consultants Ltd., and Bangladesh Engineering and Technological Services, Dhaka, Bangladesh. April 1992. pp. I 04.

Department of Fisheries (DOF), 1990. Manual of catch assessment survey, Fisheries Resources Survey System, Department of Fisheries, Dhaka, Bangladesh. November 1990, pp. 122.

FAP-6. 1993a. Fisheries specialist study, draft final, Northeast Regional Water Management Project (F AP 6). Shawinigan Lavalin (1991) Inc., Northwest Hydraulic consultants Engineering and Planning Consultants Ltd., Bangladesh Engineering and Technological Services and Institute for Development Education and Action. (Canadian International Development Agency). April 1993. pp. 291.

124 M. YOUSSOUF ALI

FAP-6. 1993b. Wetland Resources Specialist Study- Draft Final, North East Regional Water Management Project (FAP 6). Shawinigan Lavalin (1991) Inc and North West Hydraulic Consultants and Local associates. April 1993 (Canadian International Development Agency). pp. 106.

Karim, M. and Ahsan, A.K.M., 1989. Policy recommendations on fisheries development on Bangladesh, Ministry of Fisheries and Livestock, Government of Bangladesh.

MPO, 1986. Final report. National water plan, I, Sector Analysis. MPO. pp. 260.

MPO, 1987a. Openwater capture fishery resources, Technical report 16, pp. 35.

MPO, 1987b. Fisheries and flood control, drainage and irrigation development. Technical Report 17, pp. 54.

Rahman, A.K.A., 1985. Introduction of exotic fishes in Bangladesh. Paper presented in the seminar on Culture Need of Exotic Fishes in Bangladesh organised by the Zoological Society of Bangladesh. Dhaka University.

Rahman, A.K.A., 1989. Freshwater fishes of Bangladesh, Zoological Society of Bangladesh, Department of Zoology, Dhaka University, Dhaka, Bangladesh, pp. 364.

Rashid, H.E., 1991. Geography of Bangladesh (Second Revised Edition), University Press Limited, Dhaka, Bangladesh. pp. 529.

Sarker, M.S. and Sarker, N.J., 1988. Wildlife of Bangladesh -A systematic list, Rico Printers, Dhaka, Bangladesh.

Tsai, C., Khan, A.A. and Halder, G.C., 1978. Prawn nursery ground investigation of the Feni Estuary (Bangladesh) with reference to Impacts of the flood control project. I. Mar. Ass. India 20 (1.3):1-9.

Welcomme, R.L., 1979. Fisheries ecology of floodplain rivers, Longman Group Limited, London, UK. pp. 317.

World Bank, 11989. Staff appraisal report on Fisheries III Project, pp. 54.

ADAPTATION TO CLIMATE CHANGE IN BANGLADESH: FUTURE OUTLOOK


MOZAHARUL ALAM Research Fellow Bangladesh Centre for Advanced Studies (BCAS)

A. A TIQ RAHMAN Director Bangladesh Centre for Advanced Studies (BCAS)

1. Introduction

The human induced climate change is no longer a theoretical concept. There is a global consensus among scientists, professionals, academics, policy makers and strategists that the globe has already committed to certain degree of change in climate system. Climate change will affect all human and ecological systems and socio-economic development activities. Pressure has been mounting on the global leadership to take necessary steps in response to changes in climate system.

Response options to climate change are those which would modify the effects of agents of change and effectively reduce consequential vulnerability. In general, there are two broad types of response options, namely mitigation and adaptation. Mitigation entails actions that are aimed at preventing or retarding the greenhouse gas (GHG) emissions. Adaptation is defined as "any adjustment - passive, reactive, or anticipatory - that can respond to anticipated or actual consequences associated with climate change" (Carter, 1996).

Mitigation, in one hand, can only slow down the rate of climate change and can not prevent its occurrence. Since mitigation activities do not ensure reduction of relative vulnerability of a person on an individual level, many people, especially those in the least developed countries, would be sceptic about committing to consider mitigation option(s) for the global benefit. Adaptation options, on the other hand, can reduce vulnerability to some extent on an individual level. More importantly, the positive effect of committing to adaptation practices by an individual or a community would have immediate visible impacts. Therefore, adaptation to climate variability and change is more likely to occur.

125

126 A.U. AHMED, M. ALAM and A. A. RAHMAN

Adaptation, in general, is a basic process of life and occurs in a wide variety of ways and under many circumstances. Depending on the types of impact many activities may be identified as elements of adaptation that would reduce the vulnerability, enhance resilience capacity and enforce changes to protect from exposure to adverse impact. The following four defmitions will provide an essence of ideas which are included under the jargon adaptation:

"Adaptability refers to the degree to which adjustments are possible in practices, process, or structures of systems to projected or actual changes of climate. Adaptation can be spontaneous or planned, and can be carried out in response to or in anticipation of changes in conditions" (Watson et al., 1996).

"Adaptation involves adjustments to enhance the viability of social and economic activities and to reduce their vulnerability to climate, including its current variability and extreme events as well as longer term climate change" (Smit, 1993).

". . . the term adaptation means any adjustment, whether passive, reactive or anticipatory, that is proposed as a means for ameliorating the anticipated adverse consequences associated with climate change" (Stakhiv, 1993)

"Adaptation to climate is the process through which people reduce the adverse effects of climate on their health and well-being, and take advantage of the opportunities that their climatic environment provides" (Burton, 1992)

Ever since the global concerns have been raised about the adverse impact of climate change, the global community has cited Bangladesh as one of the most vulnerable country. The reasons are obvious. It is highly vulnerable, even under no-climatechange, due to many factors including its disadvantageous geographic location, flat and low-lying topography, high population density, rampant poverty, chronic inefficiency regarding institutional aspects and poor state of economic development. The magnitude of vulnerability would just increase manifold due to the impacts induced by climate change. Recent studies suggest that all such factors would exacerbate the adversities for the poor people of Bangladesh under climate change scenarios (BCAS/RA/ Approtech, 1994; Huq eta/., 1996; Warrick and Ahmad, 1996, Huq eta/., 1998).

The country has very limited scope in order to respond to imminent danger. Since its per capita greenhouse gas emission is one of the lowest in the world while the total annual emission is insignificant to the global annual load (Ahmed eta/., 1996), it can not offer any appreciable mitigation at the global level. On the other hand, since its people would suffer the worst due to high level of vulnerability, it has no other choice but to consider some adaptation options and examine whether those might result in any significant reduction of anticipated vulnerability. This article examines the possibilities, opportunities and challenges of adaptation to climate change for the people of Bangladesh.

ADAPTATION AND FUTURE OUTLOOK 127

2. Vulnerability to Climate Change

The first step of identifying adaptation options is to identify the causes and implications of vulnerabilitY regarding physical systems, natural ecosystems, socio-economic conditions and institutional aspects of the country. A brief description of different types of impact and related vulnerabilities, which are of major concerns for Bangladesh, is presented below.

There are some agents that force the climate system to change. In most of the impact studies carried out so far the agents of climate change have been expressed in terms of variables such as temperature, precipitation, evaporation and river discharge etc. General Circulation Model (GCM) analysis revealed that there would be a general warming throughout the country. The average temperature increase would range from 1.3°C to 2.6°C. The total annual precipitation would also be increased, but the distribution would be different for the monsoon and winter seasons. In one hand, monsoon precipitation would increase significantly, while on the other, precipitation in winter would decrease. Higher precipitation in monsoon would cause increased volume of runoff in the surface water systems, resulting into severe floods in many parts of the country. The combination of elevated temperature and decreased precipitation in winter months (December -February) would cause a manifold increase in potential evapotranspiration. The latter effect would cause moisture stress in the western parts and salinity intrusion in the coastal areas of the country (Ahmed and Alam, 1998).

A combination of effects of climate change, confmements of river courses, increase in riverbeds due to continued sedimentation and sea level rise induced backwater effect would eventually increase both the frequency and severity of floods in the country (Huq et al., 1996). Analysis suggests that floodplains of Lower Ganges and Surma basins would become more vulnerable compared to the rest of the country. On the other hand, the north-central region would become flood free due to embanking the major rivers (Alam et al., 1998). A recent modelling exercise revealed that, about 10 per cent increase in precipitation results in a 20 per cent increase in inundated area (Hagler Bailly andBCAS, 1998).

The most significant climate change induced impact would be on crop agriculture sector. As it has been argued, the positive effect of carbon-di-oxide fertilisation would not be adequate to offset the anticipated loss in foodgrain production due to other associated problems including degradation of topsoil, depletion of organic matter content, moisture stress and phenological drought, salinity intrusion etc. (Karim et al., 1998; Habibullah et al., 1998). All the anticipated adverse impacts would have devastating effect on foodgrain production of the country.

Sea level rise would cause recession of flat sandy beaches in the south-eastern part of the country while increased magnitude of cyclonic storm surges would inundate the coastal unprotected lands with saline water (Islam et al., 1998). The forest ecosystems of the country would suffer due to floods in monsoon and moisture stress in winter. The ecological security of the largest patch of productive mangrove in the world, the


Sundarbans, would be at risk due to a combination of low-flow and salinity intrusion in winter (Ahmed, 1998).

The major elements of vulnerabilities for Bangladesh are, therefore, related to water and crop agriculture. There are too much water in the monsoon and too little in the winter. In both the cases agricultural production would suffer severe losses and the food security of the country would be under tremendous threat. Floods and cyclonic storm surges would force many people to become environmental refugees, while agricultural production loss would destabilise food security and increase hunger. All these would translate into increased economic hardship and social unrest. The interactive relationship among the primary physical effects those would be influenced by climate change in two different seasons, monsoon and winter, are presented in Figure-la and Figure-1 b, respectively.

FIGURE la. Pathway of impacts of water in monsoon

Too much water in monsoon

Bed levels

Sea level rise

>>

>>

Precipitation

>>

Protected area: risk of

flooding

Unprotected area: bank overflow

Water logging

>>

>>

Sedimentation in floodplains

<<

Impacts on flood

>> : Increase expected << : Reduction expected

The people of the country are already fighting against poverty, hunger and malnutrition. The existing institutional arrangements are not conducive to ease the hardship of the people. Due to inherent institutional inefficiencies and weaknesses in managerial capacities to cope with the anticipated natural events, it would be extremely difficult for the country to reduce vulnerability to climate change.

ADAPTATION AND FUTURE OUTLOOK

FIGURE lb. Pathway of impacts of water in winter

Too little water in winter

Upstream developments

Water requirement for irrigation

>>

Water requirement

for pisciculture

Water

demand

>>

>>

>> Low water availability

>>

>>

>> : Increase expected << : Reduction expected

129

In this backdrop it appears to be extremely useful to identify a number of adaptation

options, especially for water and agriculture sectors, which would facilitate the people of

the country to come out of the stranglehold of impact of climate change. To this end one

may evaluate a number of options and identify the actors who would implement the

perceived options. In the following sections, a brief assessment on the potential adaptation

options for water and crop agriculture sector is presented:

3. Response to Climate Change

Very recently a study was carried out to fmd out mitigation opportunities for Bangladesh.

It was reported that, although there could be as many as fifty seven mitigation options, the

overall mitigation potential was very low. Some of the identified activities could perhaps

save a few giga-gram carbon-di-oxide equivalent, the emission would not be significant

with respect to the global emission (BCAS/BUET/BIDS/BUP, 1998). Therefore,

implementation of mitigation options would not reduce vulnerability of the country. In

contrast, it is expected that implementation of adaptation options would enable the

affected people to reduce vulnerability to a significant extent.


3.1. TYPES OF ADAPTATION

There may be two broad types of adaptation: spontaneous and climate change awareness induced adaptation (Burton, 1997). Spontaneous or autonomous adaptations are adjustments· that are considered spontaneously to cope with gradual changes in climate system. Such adjustments are either unconscious or automatic reactions of an exposure unit to climatic perturbation, or conscious responses to variations in climate that are part of the routine functioning of a system, or responses requiring a behavioural change (Carter, 1996). From prehistoric time human beings have been practising all the three types of spontaneous adaptation with many changes in climate system. Many of the present day human activities carry signs of ancestral behaviour, only modified according to necessity and advanced with the assistance of technologies available.

3.2. ANTICIPATORY ADAPTATION MEASURES

There are potentially a very large number of adaptation measures and the IPCC Working Group II identified 228 different measures (UNEP and GEF, 1996). These measures may be classified into the following few groups:

3.2.1. Bear Losses It is an adaptation response that entails "doing nothing" except accepting the losses. Cost bearing might be observed when the costs of adaptation would appear higher than the anticipated loss or the impacted human system would not have any capacity to respond. If an investment is made in a vulnerable location and the expected rate of return would surely surpass the possible damage due to impact of climate change, the investors might decide to have "no adaptation" policy. Such adaptations are strategic.

3.2.2. Share Losses Sometimes preparing to share the anticipated losses among the stakeholders may be more preferred than the other available adaptation options. Such options are anticipatory in nature and well thought out. Provision of insurance has already shown how such a measure may be adopted. Providing subsidies to people living in identified vulnerable areas and increase tax for those living in more protected areas could be one such measure that may be implemented by local and/or central government. Sharing the losses from climate change can be very local affair and can extend to the world-wide family of humanity.

3.2.3. Modify The Threat If the nature and extent of the threat is known it would be possible to modify it with adequate precautionary measures. Such measures may be both spontaneous and awareness driven. Switching to alternative cropping pattern in agriculture sector, building a breakwater in an island to safeguard tourism and industries etc. could be regarded as modifying measures.


3.2.4. Prevent Effects There might be some adaptation measures aimed at preventing the adverse impacts of climate change. Preventive measures, by defmition, can not be spontaneous and may require long time and large-scale investments. Such measures often involve government's planning and support from international community. On the other hand, implementation of such measures depend on technical feasibility, institutional capacity to implement and fmancial viability. Building oflarge embankments to protect from enhanced flooding may be cited as an example of preventive measure.

3.2.5. Change Use In case the imminent danger makes it impossible or extremely risky ·to continue the economic activity, the next available option would be to change the use of such activities. In some cases such measures might lead to relatively higher economic returns and open up new opportunities. In low-lying coastal areas agricultural lands might be subjected to submergence and that may allow the local people to grow shrimps in the newly submerged areas. In some other cases the economic return from altered uses might not be attractive: a saline impacted coastal cropland would not maximise social goods and services if it would be converted to pasture.

Effective use of such measures depends on thorough knowledge on type and extent of vulnerability, alternative options and willingness of the stakeholders to accept the planned alternative uses.

3.2.6. Change Location In a country where population is dispersed and density is low, relocation might be technically viable. But such a measure might not be socially accepted and therefore, planning for relocation has to be done through social consultations. For vulnerable industries, especially those situated in the coastal areas, relocation might be the only viable solution. But relocation of a culturally sensitive element might not be easy, requiring consensus among all the stakeholders. Opting for relocation might necessitate long-term planning involving the actors at national and sub-national (district) levels and in many cases, financial assistance from the international community. On the other hand, changing location might be a spontaneous adaptation measure in the highly vulnerable areas and people might become "climate change refugees"(UNEP and GEF, 1996).

There may be other measures, known as restoration, "which aims to restore a system to its original condition following damage or modification due to climate". Such measures, however, may not offer effective adaptation, "as the system remains susceptible to subsequent comparable climatic events" (Carteret a/., 1994).

Activities that would enable an individual or a society to adapt to the altered climate scenario and its impact, can not be designed to cater the needs of that individual. Rather the activities should be identified and directed to satisfy the needs of at least a significant fraction of a community.


3.3. POSSIBLE ACTORS AND THEIR RESPECTIVE DOMAINS

The actors or the key players in managing adaptation for an impacted community and/or the respective government would take adaptation measures depending on the location specific impacts. The anticipated impacts, however, would take place at different levels. Occurrence of climate change induced increased ice melt and volume of water in the oceanic system is an example of change at mega (global) level. Some changes are anticipated within a particular region, sub-region or country. For example, increased ice melt and rainfall in the Himalayas would affect surface and groundwater hydrology of the rivers and floodplains of China, India, Nepal, Bangladesh, Bhutan and Pakistan. Each of the co-riparian countries would experience somewhat similar impact, especially during monsoon. Such a change and its impacts would be observed at macro (country/regional) level.

Within a country, however, different communities would experience different types of impacts depending on geomorphology and physiographic characteristics of the area. Adaptation measures to reduce such location specific impacts would have to be considered at meso (community) level.

The ultimate impacts would be observed at the bottommost level, known as the micro level, where small family units and individuals would experience changes in the physical system and consider adaptation options. The impacts at the micro level would always be observed irrespective of the origin of the processes.

Since the impacts would be observed at four different levels, mentioned above, the management aspects of adaptation would depend on actions taken/considered at all those levels. Figure-2 shows the interactive management of adaptation at different levels.

3.3.1. Global Level The leaders of the global community are the actors at global or mega level. The political leaders are involved in modifying (reducing) the threats through the provisions made by the United National Framework Convention on Climate Change (UNFCCC) and the Conference of the Parties (COP). Although there had not been any discussion on country specific adaptation, they have reached a general consensus and committed, on behalf of their respective governments, to provide " ... costs of adaptation ... " in developing countries (Article 4.4, UNFCCC).

The global scientific community has played a significant role in identifying, evaluating and promoting adaptation measures for vulnerable countries. Their collaborative efforts have been culminated into the Second Assessment Report of the Inter-governmental Panel on Climate Change (IPCC) where many regions specific adaptation techniques are mentioned. The enactment of IPCC, COP, SBSTA, AGBM etc. and the GEF together gave the global institutional set up for possible global level adaptations. Such bodies have been contributing by commissioning research to understand the vulnerabilities of climate


change at the global, regional, country and community levels; formulating policies to facilitate adaptation at country and community levels; making provisions for " .. new and additional funding .. ", as promised in the UNFCCC, to ensure that adequate adaptation measures are considered in achieving country specific sustainable development and formulating a mechanism to monitor implementation of adaptation at the community levels.

FIGURE 2. Different levels of interactive management of adaptation

GLOBAL LEVEL

I I Mega • UN,UNFCCC,CSD WTO, WB, IMF,

International Civil Society

REGIONAL LEVEL

l Sub-Mega r ADB, ESCAP, APNCSD

~ r--. APEC, SAARC

Super-Macro Regional Civil Society

I Macro I NATIONAL LEVEL

1 National Government National Civil Society

SUB-NATIONAL LEVEL

I Meso I District, Local Govt.

l River Basin Eco-specific

I Micro I LOCAL LEVEL

Community, Family Individuals

3.3.2. National Level The Government of Bangladesh (GOB) is the actor that would consider adaptation activities at the macro or national level. The GOB would provide with appropriate, ecospecific, people-centred and need-based adaptation plans, adequate legal and institutional framework for managing adaptation strategies. The government would not only devise national plans for adaptation, it should take necessary steps to implement the plans involving its functionaries. The central government, however, should monitor and ensure that the plans are implemented with active participation of the local communities and individuals.


3.3.3. Sub-national Level Local government institutions are those which would operate at meso (sub-national or district) level. In managing adaptation in a country they would perform roles of intermediators between the government and the people. They would ensure that local institutions, pressure groups and non-government organisations work together for implementation of adaptation measures. They might organise needs-based adaptation training sessions to help accommodate adverse impacts of climate change; transfer technologies that assist appropriate adaptation; help people to relocate and retreat in an event of disaster; implement local level projects to protect from possible unavoidable impact etc. Simultaneously, such agencies would update the situation and keep the government informed about the adequacy of adaptation measures, needs of the people at the local level and requirement of funding etc. Depending on the available support from the central government, they would implement local level adaptation plans.

3.3.4. Local Level The grassroots people and families operate at the micro (community/individual) level. Individuals and families might provide valuable information in defining vulnerability, identifying and prioritising adaptation measures. In planning and implementation of any adaptation measure, preventive or accommodative, people's participation and feedback is a must. But their efforts would have to be reinforced by making adequate provisions of knowledge, technology, policy and financial support.

Adaptation at the micro level often takes place spontaneously. People at the grassroots often adjust to a given situation on a short-term basis and such adaptations often follow the cycle of act-learn-act. People learn from their mistakes and their efforts often remain unnoticed. They can, however, play significant role in formulation of adaptive plans and implementation of those sector specific plans. In order to strengthen micro level adaptation it would be necessary to combine lessons that have already been learnt and integrate the efforts of local people with that of the actors at all other levels.

3.4 OPPORTUNITIES FOR BANGLADESH: AN ASSESSMENT

The above mentioned adaptation measures have been assessed based on the level of economic development, population density, poverty, possibilities of increasing landmass of the conntry and other institutional requirement. It is also to be noted here that this is an indicative assessment. Theoretically, it would be possible to implement all the above mentioned options in any society. In case of Bangladesh certain anticipatory adaptation options could be implemented, while for certain other options, it would be rather difficult to implement and manage.

Possibilities of awareness induced adaptation with respect to known socio-economic activities in Bangladesh are presented in Table-1. Bearing ·loss is an adaptation category that relates to accepting loss on an individual level. It would be highly difficult for subsistence farmers to accept losses in foodgrain production. Changing use or location as means of adaptation would also be difficult. These might involve enormous opportunity costs, destabilise social harmony, induce over-exploitation of natural resource base


including ecosystems and have in-built capacity to counteract sustainable development. Such measures might lead to maladaptation.

Sharing loss with other members of the community could be a viable option. Applicability of loss sharing measures depend on capacity of the stakeholders to sustain even after incurring losses and willingness of other communities to share such losses. It might, however, require good institutional support and social harmony to accept the consequences and government policy directives as a framework to provide compensation to the impacted individuals/ communities. Sharing losses through adequate provision of insurance could also be tried. It might be- difficult for an individual subsistence farmer to pay premium, even if the amount appears to be nominal. A farmers' co-operative, on the other hand, would be in much better position to pay the premium and face the adversities collectively. If the non-government agencies at the grassroots continue to provide microcredits for the farming communities, then implementation of such adaptation measure would be facilitated.

TABLE 1. Possibilities of awareness induced adaptations with respect to socio-economic activities

Socio-economic activities Awareness induced adaptation possibilities Bear Share Modify Prevent Change Change losses losses the threat effects use location

Crop Agriculture I farming Unc * * + + Q Livestock rearing + + * Q + Q (managing grassland, rangeland etc.) Fisheries management Open water (capture) fisheries

Sweetwater + + Q Q + Brackish water Q Q Q + Marine Q Q Q

Culture fisheries Sweetwater + + * + + Q Brackish water + "' + + Q +

Water resource management + * * "' Unc Physical infrastructure + + "' + Unc +

development Forest management + + * Unc + Energy production and + + * Unc Unc Unc

management Industrial activities + * Q Unc Q + Transport & communication + + * + Q + Health and sanitation Q Unc + Q

management Settlement + * * + Q + Trade + * Q Q Q + Tourism and recreation Q * + Q Q +

Notes: + means adaptation is possible. means adaptation highly possible;

Q means adaptation possibility is questionable Unc means uncertain possibility and means limited to no adaptation.


Modifying events and preventing effects are adaptation techniques that enable loss minimisation and/or reduction. It is possible to modifying the anticipated threats by any individual, community and government, although the level of success would depend on the preparedness. The unique feature of modifying the threat is that, it might be approached collectively as well as individually. From management point of view this feature is particularly important for Bangladesh. Since the 22 million households operate on their own, modifying the threat to agriculture might be approached on an individual basis depending on the fmancial and institutional strength of the household.

On the other hand, modifying the threats of flood in monsoon or that of low-flow in winter might require huge investments, preferably by the government in association with international development partners. The latter might be completely beyond the capacity of the individual farmer or household to implement. Many such measures could be technology oriented, might require adequate knowledge for management and large capital investment.

The past experiences of Bangladesh in dealing with natural disasters suggest that modifying the anticipated threat would be quite feasible. It might require pro-active people-centred planning, adequate fmancing and a good technical and institutional framework.

Qualitative assessment of some identified adaptation options with respect to water and agriculture sectors is presented in Table-2.

TABLE 2. Some identified adaptation options with respect to water and agriculture sectors

Agents of change Type of adaptation Adaptation options Level Floods (excess Prevent effects Flood control infrastructure L surface runoff) Modify threat Improvement in warning system R, N

Modify threat Building flood tolerant infrastructure S-N, L Share losses Insurance (crop loss, homesteads etc.) L, I Share losses Provide relief, credit for rehabilitation L, I Share losses Rescheduling crop calendar L, I Change use Alternate cropping practices L, I Change location Flood evacuation centres L, I Change location Taking refuge in boats I

Drought (moisture Modify threat Increased irrigation L,I stress) Modify threat Holding water in barrages in winter G,N

Modify threat Augmentation of surface flow G,R Prevent losses Drought tolerant cropping practices L, I

Salinity Modify threat Augmentation of surface flow G,R (insufficient Modify threat Holding water in barrages for winter G,N flushing with Prevent losses Salinity tolerant crop/variety selection L, I surface flow) Change use Alternative land use L,I

Notes: G: Global, R: regional, N: National, S-N: Sub-national, L: Local and/: Individual

Knowing that climate change would cause serious impacts on human systems, it is likely that people would assess the needs for continuing their activities in the future and adjust


accordingly. Such adjustments are totally anticipatory and therefore, might necessitate research, formulation of strategies and plans, allocation of adequate funds to carry out planned activities and implementation of planned program. Since such adjustments are induced by awareness regarding impact of climate change, the first step would be to make people aware about the impact and what adaptation options would be available for them. The pre-requisite of raising awareness is to undertake research on all possible aspects of climate change and determine alternative actions that would lead to least exposure to adverse impacts.

3.5. CHALLENGES OF MANAGING ADAPTATION

The process of adaptation management may depend on many factors, including who or what adapts, what they adapt to, how they adapt, what resources are used and how, and many others themes (IPCC, 1998). These related themes are part of a model, shown in Figure-3, an adaptation cycle that changes through time and space. This adaptation cycle is iterative, dyilarnic, interconnected, non-linear, and likely chaotic. Adaptation framework organised under three main categories with sub-categories is shown in Figure-4.

FIGURE 3. The adaptation cycle through space and time

How well do they adapt? (evaluation)

Source: IPCC, 1998

Managing adaptation in Bangladesh, especially by the government, would potentially be a difficult task owing to its inefficient institutions and weak fmancial capacities. Adaptation thorough protection would only be possible if foreign assistance is made available. Internationally, bi-lateral and multi-lateral frnancial mechanisms for effective mitigation measures such as Activities Implemented Jointly (AIJ), despite having criticisms, are already in place. On the other hand, very little have been achieved so far in formulating a mechanism of international fmancing for effective implementation of location/country specific adaptation options. Unless such mechanisms are developed, it would be difficult for the GOB to plan for an comprehensive adaptation strategy.


FIGURE 4. Framework for managing adaptation options

Source: IPCC. 1998

Sta keh old ers Traditional , Current and Future

Know ledge-1 n formation-Data-Models

D ecis ion-Ma kers G loba l Conventions/ a tiona I Strategies

Implementation

Communication Education

Another problem would be to integrate adaptation activities throughout the country. It is perceived that the local government bodies would be able to play a vital role in integrating local level adaptation needs in planning for a sustainable future . The usual top-down approach considered by the decision-makers could act as a potential barrier for integrating need-based adaptation options in the national development plan. This may be overcome by effective participation of communities and pressure groups in building national consensus for considering bottom-up planning approach.

4. Way Ahead

Adaptation in human systems illustrated that a combination of socially mobilised community, innovative and cost effective institutional infrastructure, information based on socially acceptable practices and appropriate scientific validation are some of the pre-requisites for successful adaptation strategy.

Glantz (1988) gave the idea that lessons can be learned from past experience and applied to future situations to enable forecasting by analogy. All socio-economic sectors are adapted to some extent to climate, and these adaptations have to be changed to fit with new conditions of a changing climate. The insights found in "natural learning" processes of a society may be incorporated into political debate or public understanding, to come to a national consensus. Such a consensus may provide the policy framework, on which the adaptation plan would be formulated.

It is often perceived that climate change is a distant phenomenon to occur many decades latter. However, people in vulnerable communities are quite accustomed to copping


with long time phenomenon, uncertainties and variability in climate and its consequence. Hence responding by evolving appropriate adaptation strategies and actions are not only a regular feature in their lives but an essential feature for survival and successful livelihood management. For example, in the devastating flood of 1998 , many farmers modified their crop calendar to enhance horticulture when they realised that they missed the plantation of the main crop i.e. rice. Many have also planted delayed rice seedlings in the fullest knowledge that it will result in a lower yield but will contribute significantly to their survival.

The people of Bangladesh have been experiencing calamities of nature, often induced by climate systems, since time immemorial. Their resilience has always been phenomenal. A lot of adaptation techniques, often proved to be useful in real life situations, are being practised by the grassroots people. If people at the grassroots get to know what types of vulnerability they are about to face, especially if they are provided with early warnings about primary physical effects (floods, flash-floods, droughts, salinity intrusion etc.), they would adapt to the adversities fairly quickly. The process might be facilitated with wide-scale awareness raising programmes and appropriate training.

Awareness raising, however, should not be confined among the villagers. Rather, a campaign should be targeted for almost everyone in the society: the politicians, the policy-makers and public administrators, members of the pressure groups, professionals and researchers and individuals. Adaptation would be highly possible if the processes are well accepted by everyone in the society. It would also make the bridge between all individuals in the country, irrespective of their status of vulnerability due to climate change, and bring about national consensus - the basic force required to face climate change related adversities. A wide-scale awareness raising campaign should be considered as a short to medium-term activity.

It is also important to have appropriate policy framework to fight back adversities and restore social harmony within the country. Since the government assumes the responsibility of taking care of its citizens, it should get prepared for taking adaptation measures, in most cases anticipatory adaptation measures, for the well-being of its citizens. The policy might consider offering crop insurance at low premium rates, exemption of local taxes following a natural disaster or crop loss in a particular area, raising the coastal embankments to avoid saline water inundation into the crop lands etc.

Policy formulation could be a dynamic process and policies should be flexible to accommodate the needs of the people. Evolution of appropriate policy might take a long time and a better policy might be achieved only through effective application of "act-learn-act" method.


Adaptation could be highly facilitated by research and extension. Flood forecasting has been possible in the country through collaborative research. The activities have to be intensified just to get adequate feedback in appropriate time. Research is needed to analyse whether the existing embankments would perform well under a given climate change scenario, how the autonomous adjustments could reduce the increased vulnerability due to climate change etc. In the field of agriculture the scientists have already succeeded in developing many varieties suitable for particular agro-ecological zones. The efforts have to be extended to develop drought, salinity or flood tolerant crop varieties etc. Research could be considered as medium to long-term activity. Since Bangladesh have been experiencing disasters of many dimensions and in most cases these refer to either agriculture or water sector, the GOB has constituted a number of research institutes. Although the financial arrangement is far less than adequate, still the eleven institutions under the National Agricultural Research System are trying hard to adapt with the prevailing environmental and social conditions of the country. Similarly there are research organisations for the water sector also. In addition to these a number of non-government and private research institutes have been engaged in research in recent years.

Research alone would not be able to guarantee successful adaptation. Without countrywide extension, especially in case of agriculture, it would be difficult to mobilise the farmers to try with an alternative package of technology. Fortunately, there is a Department of Agriculture Extension under the Ministry of Agriculture. It could play a vital role in providing extension services throughout the country.

Following the devastating cyclone in 1991, which caused death of about 138,000 people in the coastal districts, the government and the non-government agencies built about 2,500 new cyclone shelters at the remote areas of the Bay. During 'normal' times, these are used extensively as primary level educational institutions and community centres. Simultaneously, advancement regarding telecommunication and satellite based remote sensing analysis has been made by the relevant government institutions. Meanwhile, the local non-government agencies imparted training on how to save valuables and lives during cyclones. A combination of all these proved to be extremely useful when two cyclones of similar intensity as in 1991 hit coasts of Bangladesh in 1994 and 1998, respectively. The death toll remained below 100 in both the events. It appears that a combination of structural measures such as building embankments and other infrastructure along with non-structural measures such as early warning, evacuation and taking refuge to shelters provided a good adaptation option for the people living along the roving shore.

The previous experiences in reducing adverse impacts of natural calamities suggested that anticipatory prevention of the effect could be beneficial for Bangladesh. During the devastating floods of 1998 very little damage had been recorded in the business district of Dhaka due to an embankment that was created only nine years ago. On the contrary, the same area was completely under water in a similar event in 1988 in the absence of the embankment. The anticipatory adaptation, in this case, was paid off by reducing the impacts of flood.


Similar approach might be considered for flood affected people. Land under settlement which are susceptible to flood could be raised by filling up low-lands with soil from excavation of rivers and canals and/or by creating new community ponds. This would enable faster recession of flood water while the latter would provide sources of water during winter. On the raised grounds infrastructure, similar to the multi-purpose cyclone shelters, could be built all around the country. During normal times these could be used as schools, while during severe floods these could be utilised as temporary refuge for the affected people.

In conclusion it is the effective interaction between the clarity of scientific information, adaptation actions, mobilised populace, favourable and responsible institutions and change agents and a supportive policy framework nexus that is necessary for a long term and sustainable adaptation strategy to climate change and its impacts. The lessons learnt from climatic variability could be helpful in developing adaptation strategy to climate change. Local level institutions, research organisations with linkages to worldwide scientific and policy community should be supported to lead this multidisciplinary research area. The Kyoto Protocol in Article 12(8) has emphasised the need for more actions and support for adaptation activities. Countries such as Bangladesh whose contribution to climate change through GHG emission is negligible and are disproportionately impacted by global climate change consequences such as sea level rise and enhanced extremes weather events ( viz. floods, cyclones tidal surges, droughts) must be supported by the global community to take a leadership role in the development of the science and policy of adaptation. Institutional capacity building, human resource development, indigenous approaches linked by closed interaction with the global community is probably the best investment for learning about adaptation and developing the future course of action. Bangladesh can offer a leadership role in this area.

References

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Subject Index

A Community 125, 126, 131, Accretion 72, 75, 76, 77, 132, 134, 135,

78,79,91,92 136, 138, 140 Adaptation Strategy 137, 138, 141 Community Participation 101 Adaptation I, 8, 9, 10,125, Crop Response Functions 57,58

126, 132, 134, Cropping Season 40 136, 137, 138, Cross-Sections 27 139, 140 Cultivable Lands 56

Alluvium 56 Cyclone 140, 141 Ambient C02 101 Awareness Induced D

Decadal Rate of Change 15, 16 B Deciduous Tree Species 95 Bathymetric Information 71 Deep Sea· 80 Bear Losses 130 Deforestation 94,98,99,101 Bed Level Change 27 Depression 2,4 Bengal Basin 2 Depth of Inundation 22,23,29,38 Bengal Deep Sea Fan 73,91 Desiccation 56,57,59 Biomass 99, 102 Development Scenario 21 Brackish Water 113,116,119, Digital Elevation Model 27

121 Discharge Current 78 Brunn's Formula 71, 81, 82, 85 Discharge Values 21

Dominant Species 95,97,106

c Drought 40, 41, 42, 49,

Canopy Closure 101 51, 52

Capillary Action 42,56 Capture Fisheries 114 E C02 39 Ecosystem Productivity 101 Change Location 131 Equilibrium Response 14, 15 Change Use 131 Erosion 75, 76, 77, 78, Changes 79,80,82

In River Water Level 21,22 Estuaries 113, 114, 117, In Soil Moisture 22 121 In Water Level 26,27 Estuarine Fishes 119

Circulation 4 Evaporation 13, 14, 17, 18, Climate Change Scenario 14, 21, 38 19 Climate Change I, 7, 9, 10, 21, Evapotranspiration 42,43,56,59

23, 55, 65, 93, Existing Land Area 31 104, 125, 129, Exotic Species 113, 120 134, 138, 139 Extremely Vulnerable 9,28,33

Climatic Parameters 21,23,94 C02 Fertilisation 43,47,48,49 F Coastal Areas 56, 57, 58, 59, Fish Habitat 114

65,66,69 Fish Species Diversity 117 Coastal Belt 123 Flash-Flood 40,41,49

Flood 40, 41, 42, 43, 47,48,49,52

145

Flood Action Plan 23,26,28 J Flood Protecting Juveniles 117,120,122 Infrastructure 22 Floodplains 2, 9, 113, 114, K

115, 116, 118, 119, 120

Koppen's Index 18

Flow Velocities 26 L Fluctuations Of Values 23 Land Loss 71 Food Security 128 Land Type And Area Forest Ecosystems 94, 95, 98, 102, In 2030 33

103 In 2075 36 Forest Succession 107, 108, 127 Land Type Change Matrix 25, 28, 29 Freshwater 113,114,116, Land Type Database 21,25,28,29

117,118,119, Larvae 113,117,120, 120, 121 122

Fry 117 Legal State Forest 94 Logarithmic Trend 29

G Low-Flow 41,47,49,94 Ganges-Brahmaputra-Meghna 56, 115 M General Circulation Mangrove Ecosystems 93, 102, 103 Model 9, 19, 21, 23, Mangrove Forest 73, 75, 93, 97,

39,45 103, 104, 123 General Model 23,25,26,38 Mean Sea Level 2 Geographic Information Mesohaline Zone 105 System 21,27 Meteorological Variables 14 Germination 62,65,67, 70 Micro-Nutrients 41 Global Warming 1, 94, Ill MIKEll 21, 22, 23, 24, Growth Rate 102 25,26,27

Mitigation I, 125, 126, H 129, 137 Human Encroachment 94,97 Moderately Vulnerable 28,33 Human Induced Modify the Threat 130 Climate Change 125 Moisture Availability 41, 43, 103 Hunge 128 Moisture Regime 39 Hydrodynamic Mode 21, 25 Moisture Retention Capacity I 02

Moisture Stress 93, 102, 108 I Monsoon Current 79 Impacts 125, 126, 127, Monsoon 13, 16, 17, 18,

128, 129, 131, 19 132, 134, 136, N 140, 141 National Programme 10

Increased Discharge 21 Natural Disaster 94 Index Of Aridity 42,56 Natural Forest Ecosystem 93,94,98,102 Indigenous Species 98, 102 Natural Hill Forests 94 Inland-Water System 117 Nutrients 41,42,48 Institutional Aspects 126 Institutional Capacity 141 0 Institutional Framework 133 Observed Average 16 Inundation 9, 10, 78, 90 Observed Values 16

146

Offshore Islands 103 Simulation Model 22,23 Oligohaline Zone 105, 106, 107 Simulation 39,43,45 Oligohaline 105, 106 Slightly Vulnerable 28,33 Organic Matter 41,42,43,49 Small-Sized Fishes 118

socio-economic p Environment 5 Photosynthetic Efficiency 52 Species Migration 107, 110 Physical Environment 2 Spontaneous Adaptations 130 Physiography 2 Storm Surges 79, 90, 107, 108 Plantation Forests 94 Subsidence 22,27 Plantation 93, 94, 97, 98, Successful-Adaptation 138, 140

101, 103 Succession 107, 108, 109 Pleistocene 2 Sundarbans 117, 123 Policy Framework 138, 139, 141 Surface Water Irrigation 42 Polyhaline Zone 105, 106 Swamp Forests 93,97 Post-Monsoon 4 Swatch of No Ground 73, 75 Potential

Evapotranspiration 127 T Poverty 5 Temperature 13, 14, 15, 16, Precipitation 4, 9, 18, 94 17, 18, 19 Pre-Monsoon 4 Temperature 94, 101, 102, Prevent Effects 131 103, Ill Primary Physical Effects 128, 139 Thinning 94,98 Private Forest 94 Tide 73, 78, 84, 85,

90 R Time Dependent 16 Rainfall-Runoff 25,26 Transient Models 14 Regeneration 102, 107' 1 08 Transient Responses 14 Regional Models 25,26 Tropical Climate 4 Research 132, 137, 139, Tropical Forests 101

140, 141 Response Options 125 u River Systems 4 Uncertainties 1, 10 Riverine Fish 123 Unclassified State Forest 94,95,97 Root Zones 41,42 Upstream Boundary

Stations 21,23 s Sal Forests 94 v Salinity Intrusion 40, 42, 49, 52, Vulnerability 1, 8, 128

102, 107, 109 Sea Level Rise 21, 22, 23, 26, w

30, 38, 71, 72, Warming Processes 15 75, 79, 80, 81, Water Depth Spatial 85, 87, 89, 90, Database 21,25,27 91, 94, 108 Water Level Values 21

Sedimentation 27 Watershed Development 23 Sensitivity 15 Water-Use Efficiency 101 Share Losses 130 Shoreline Recession 71,72,80,81 y Shrimp Farm 122, 123 Yield Reductions 45,47 Shrimp Growing Areas 123

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