GENE- INTRODUCTION

3 Mangrove Zones of t h e W o r l d

J S t a t u s of :[ndlan Mangroves

3 S t a t u s of Mangroves I n Kerala

2 S t a t u s o f Mangroves i n Cochin

;I The Maln O t ~ j e c t i v e s of t h ~ s Study

GI.: NERAL INTRODUCTION

Mangroves are salt tolerant forest ecosystem of tropical and subtropical

intertidal reglons near river mouths. Climate of any intertidal region acts as the most

significant and important factor for natural growth, development and succession of the

mangroves. Among the climatic factors, temperature fluctuations, humidity percentage,

total annual rainfall, regular wind flow, radiation and sedimentation along with upstream

water supply also play very dominant role for the growth and viability of mangroves.

Mangroves help to protect coastlines from erosion, storm damage, wave

action and cyclone. This ecosystem is a reservoir of plethora of plant and animal species.

The forest detritus. consisting mainly of fallen leaves and branches from the mangroves,

provides nutrients for marine environment, and support immense variety of sea life in

intricate food webs associated directly through detritus or indirectly through the

planktonic and epiphytic algal food chains. The mangrove wetlands offer refuge and

nursery grounds Ibr ju\:enile fish. crabs, shrimps and migratory sites for hundreds of bird

species Mangroves have also been useful in treating emuent, as the plants absorb excess

nitrates and phosphates thel-eh'y preventing contamination of near shore waters.

Mangroves cor~stitute one of the most productive zones for brackish water fishery

development hlangroves also act as barriers to prevent coastal erosion and also protect

the estuarine communities fronl natural disasters (Desa and Desa, 1982; Tomlinson,

1994, Natarajan. 1998; Naskar and Mandal, 1999).

hlangrove ecosystems have traditionally been sustainably managed by

local populat~on\ fol the production of food, medicines, tannins, fuel wood and

constructio~~ materials. Leaves of a few species are used as fodder for livestock

(Mohanan. 2000). The medic~nal properties of mangrove trees and shrubs have also been

reported Chemicals that are antimycotic, antidysentric, and other compounds having

medicinal properties as far instance for the cure of leprosy are derived from mangrove

plants. For n~illions of indigenous coastal residents mangrove forests offer dependable,

basic livelihoods and sustain their traditional cultures. These important 'land builders'

support genetically diverse comrnunities of terrestrial, and aquatic fauna and flora that are

of direct and indirect environn~ental, economic, and social value to human societies

throughout the world (Walsh, 1974; Venu. 1999).

In 1984 it was estimated that there were 171,000 sq. km. of mangrove

forest i n the %odd (Anonymous, 1987) They are scattered in Japan (Iriomote island),

Malabs~a (\latang). Indonesia Brazll (South coastal area), South Amer~ca (Wetlands in

the insular ('aribbean), Srilanka (North western coast), Saudi Arabia (Red sea coast),

Northern \'ietnam; Pakistan (Karachi), Bangladesh (Western coastal belt), Thailand,

West Africa. Ha%aii, Malaya. and India (Sharma, 1997). Global distribution of

mangroves are represented in Figure 1 . Different mangrove zones of world are detailed as

follows ( Naskar and Mandal. 1999).

hlangrove Zones of the World (after Naskar and Mandal, 1999)

CountqIZones Area ~ r n ' Country/Zones Area ~ r n ~

Indonesia 32510 Sri L'anka 32

Australia 1 1 5110 Singapore 5

Bat~gladesh 5800 Hong Kong 65

India 6'740 South Africa * Thailand 2x7:; Other Pacific Is. 100

Count n/Zor~es

Burma

Papua New Gu~nea

Ph~l~ppineh

Sabah

Madagascar Kepub

Vietnam

Pakistan

Sarawak

Peninsular Zlala~sia

Ilozamh~que

Kenya

Kampuchea

Tanzania

Neb Lealand

Fiji

Countw/Zones

Maldives

Mauritius

Seychelles

New World Mangroves

Brazil

Cameroon

Columbia

Ecuador

Gabon

Mexico

Nigeria

Panama

Senegal

U.S..A

Venezuela

Area ~ r n '

*

Vlangrove forests of .Australia are threatened by the discharge of sewage

effluent anti aquaculture wastewater leading to nutrient pollution (Boto, 1992). On

Penang Island irl north west Malaysia, the mangrove forests are reported to be

endan~el~ed d u r to shrimp farm developments (Balan, 2000). Over 400000 m2 of

mangrove i i ~ l e s ~ s \rere burnt dob+~. to reduce the efect due to the spill of crude oil in

Nigeria (Anoliylno~~s. 7000 a). I'he flood which occurred at Jakartha, the Indonesian

capital on l)ecembe13X, 1999 was reported to be caused due to the conversion of nearby

mangrove tbr-esth (Anonymous, 2000 b)

t

-- - - ---

R M a n g o \ . ~ arca

- , -

distribution of mangroves (after Naskar and Mandnl, ,999).

Status of Indian l l a ~ ~ g r o v e s

In lndia mangroves occur along both the Western and Eastern coasts.

Several studies hake been made in the western sea board in locations like Gujarat,

Maharashtra. ( h a . Karnataka. and Kerala and in the Eastern sea board in Andaman and

Nicobar islands. Sunderbans of Wesl Bengal. Orissa, Andhra Pradesh and Tamil Nadu

(Figure 2 ) l'he total area of mangroves in lndia is estimated to be 6740 sq, km. which is

about 7% of the world's mangroves. Out of these the Sunderbans of West Bengal occupy

the major area. the next being Andaman and Nicobar island, both together accounting for

80% of the mangroves in the country The remaining are scattered in the States of Andhra

Pradesh, Tamil Nadu. Orissa, Maharashtra, Gujarat, Goa. Karnataka, and Kerala

(Banerjee and Gosh. 1998). Several important documents have been produced on

distribution. chemistry, productivity, and fauna of mangrove ecosystem in India (Blasco,

1977.. 1981 . Krishnamurthy, 1975.. Krishnamurthy el nl., 1975., Parulekar el a/., 1980;

Ramadhas ul ( 1 1 . 197.1. Untawale. 1'98.1 and Untawale L./ nl., 1973; 1977). Bharucha and

Navalkar (1942) and Navalkar and Bharucha (1949) have studied the mangroves of

Bombay. and Joshi (1973) and Joshi tt/ c r l (1972) studied the mangroves of Ratnagiri

district of hlaharashtra Joshi and Jamale (1975) documented the difference in the

structure, composition. and ecophysiology of mangroves on the banks of Terekhol and

Vashisti rivers

There are 34 species reported from the west coast and 48 species recorded

form the east coast Banerjee and Gosh (1998) and Naskar and Mandal (1999) have

studied the distrlbut~or~ of mangrove forest areas and species diversity in India, which is

represented as follows

;Ilangrove Forest in lndia (after Naskar and Mandal 1999)

Name of States EAST COAST

Andaman and Nicobar Islands

West Bengal

Orissa

Andhra Pradesh

Tamil Nadu

Gujarat

Mahrashtra '

Goa

Karnataka

Kerala

Area in sq. kms.

Sunderbans, South 24- Paraganas

Mahanandi Delta, Bhitarkanika

and Manipure Estuary

C'oringa, Godavari and Krishna

Estuarine Delta

Pichavaram, Tanjore 150

WEST COAST

Ciulf of Cambay, Saurashtra and Kutch 260

Bornbay, Ratnagiri, Malvan 330

Devgad & Vijayadurg

Xlandovi - Zuari Estuary 3 8

C'ovndapur, Hanover, Malpe 90

Cochin. Vembanad, Quilon, Trivandmm, 16

Cannanore, Kozhikode, Kottayam

'rot;31 Mangrove areas in lndia

Mangrove Diversity in lndia (after Banerjee and Gosh, 1998)

Name of species East West Name of species East West Coast Coast Coast Coast

Name of species East West Name of species Coast Coast

A. ~~olrrh111.~ Wall +

Hrcrgrrit~r<r ~~nntrrorrhrza Lamk-

H. par~?florrr M'iy ht t

H. .srxarrgrr/ar Lour. t

A I ~ I C L ~ ~ I I O i~lhrr Blume +

A. marirrcr C'ierh +

A. n?crritrcr var u~.rrtrss~nm S. - '4 . offic/t~a//.s L i-

Acro.stichrrtn ernr.er/rrr L.

A. .sp~~cio.srrrii IV i I I d

IIxcoecrrrr<r trgrr//ocl~tr L.

I<hizophora r 1 ~ 1 r r ~ r r l a 1 t 1 Dl.

K. nrrrcrorrirt~r Lamk

I(. .s@lo~s~r < i ~ ~ i t Y

Sotttreratrtr trlhir Smith -

S. ezj)L"czI~r Bucli

S. C~SC'OI~II~I.\ 1..

Aegicercz.~ ci~rrr/c.r~/~r/rrnr I..

Cfle.sa//~irri~r borrc/rrt L.

('. oi.s/tr L

('tv?oy~.s dcwrrrdr~~ <;riff'.

I.)L'WIS .sitllk/~'tl.s K o s b

1). hetc,roplr~.iln li'il Id +

Heri/iera,fontes Buch.

H. litoralis Dryand.

Karrdelia catrdt.1 L.

I.rrn?itritzera 1ilIort.a J .

A~p, f r r l icarr .s Thunb.

~Yjlocarpris pat ta tnm K.

.X ntekotrgettsis Pierre.

~hes[~r.siu~~oprrltrea L.

.Yalicortricr hrachiala Rox.

I~~trluy.sotr~cr oho1lata Wall.

Hihiscrrs ~ i l iaceorr .~ L.

Irrtsra h i j rga Colebr.

Smolohrrs ccrrinntrr.~ Wal

S. gloho.srrs Wal.

Seirprrs l i t loral is Schrad.

('leroder~drotr ilrerme Gaeren.

Dnlhergio .spiirosn Roxb.

('riorps tagal Perr.

I'hoetrix /~alr ido.w Roxb .

Lrrntrritzt.rn rcrcenzosa Wild.

Cerhera ntotrghil,~ L.

Aegia/i/i.s rot tr t r t l~f i~l ia R.

(jmonntelra i r ip7 Kostel.

I/~ornoerr trrhn Schi.

Hrritirrcr katriket~sis Mj.

East West Coast Coast

+ Present

- Abserit

The Indian Mansroves comprise approximately 59 species of 41 genera

belonginy to 29 families (Venu. 1999). However Banerjee and Gosh (1998) described 65

species belonging to 3 1 families. 59 genera, and two varieties of mangroves in lndia. The

Indian mangrove area has been reclaimed continuously for excavation of brackish water

fish and praun farms, salt pans. agricultural fields, establishment or development of

harbours. ports. industrialization. urbanization and subsequent pollutant discharges

(Naskar and Bakshi, 1987). According to Jagtap c/ al. (1993) about 67% of Indian

mangrove areas have been reduced during 1975 to 1991. The devastating cyclones of

1989 and 1992 have also damased the mangroves of Sunderbans of both lndia and

Bangladesh According to Dr. Yandana Shiva and others death toll due to the October

1999 cyclone in Orissa would have been reduced if the conversion of mangrove forests

into shrimp aquaculture along its coast had been avoided (Anonymous 2000 a).

Frequency of cyclones in the Arabian sea and Bay of Bengal during the last hundred

years sho\*s an increasing loss of property (Figure 3). Patches of mangroves represented

along the hackwaters of Kerala. klaharashtra, and Gujarat are also being threatened in the

present time period (Farooqui. 2000).

Status of hlangroves in Kerala

.4ccording to authentic record, about 70,000 ha of mangroves once fringed

the backwaters of Kerala, whlch now has become reduced to 3.5% in a few isolated

patches. consisting of a few species (Mastaller, 1996). Basha (1991) reported that only

1671 ha of mangroves exist in the Kerala coast, spread over 10 districts, which are given

below

Series I : No. of'l'ersons killed: Series 2 : loss in Crores

I

Fig.3 - IAosses d u e to cyclot~es ailti storm s~~ l -gcs i l l India 1978-99(Faroocll1i. 2000)

Mangroves in the Kerala Coast (after Basha, 1991)

District Area (ha)

Fhiruvananthapuram

Kollam

Alapuzha

Kottayam

Ernakulam

Trissur

hlalappuram

Kozhikode

Kannur

Kasaragod

Total

Ihe important mangrove patches existing now in different localities of

Kerala are mangroves of Veli. Quilon, Kumarakom, Cochin, Chettuvai, Nadakkavu,

Edakkad. Pappinisseri, Thalassery, Kungimangalam and Chiteri, which requires

conservation and rehabilitation (Suma, 1995). A brief account of the mangroves of Kerala

could be found in the studies by Troup (1921), who also summarized Bourdillon's (1908)

account on kerala mangroves. Bourdillon (1908) reported the occurance of Brrigrriern

gyn~~~or / i~z i r I.at11k and two species of Rhizophoru from Quilon. Gamble (1967) also dealt

with the mangoyes of Kerala coast. Blasco (1975) recorded Acnrr~hrrs i1icrfolirr.s L. and

(7rri,hrc~ odolltr~r~ Gaertn. from the Quilon backwaters. Thomas (1962) and Rao and Sastri

(1972) recorded fron~ Veli, Th~ruvananthapuram the occurance of i<himphorn nirtcrotrnto

Lamk., R~rrr-~~~g~or~itr rtrcen~ovlr. ('erhrra o d o N ~ ~ n ~ Gaertn., 1)erri.s /r!folicr/a Lour,

Ao.o.s/ic~hr~t~r I I I L . .~i~~~rtr/ilrt.s r1icifilir1.s L. . and Avicrtrr~icr t!fficitrnlis L.

Ramachandran et ti1 ( 1985, 1986) after very detailed survey along the entire Kerala coast

reported 19 mangroves and mangrove associated species Ramachandran and Mohanan

(1987) studied the floristic characteristics of Kumarakom mangroves and critically

evaluated the impact of tourism and replantation of the existing coconut and rubber in the

mansrove localltv and the Kurnarakom bird sanctuary, based on simple biocybernetic

principles rhe Important mansrove growing regions of Kerala are shown in Figure 4

Distribution of mangroves and semi mangroves along Kerala coast is

listed as follous ( Basha, 149:!)

Diversity and Distribution of True mangroves and Semi mangroves

species found in Kerala Coast (after Basha, 1992)

True mangrove species Family Travancore Malabar Coast Coast

Actrrzrhrr\ rI1c1fo11rt.s L

Acro.s/icrtnr urr1.ertn7 L

Arg~crrzrc L~O~IIICIIIUIIIIII L.

Avicr11111(r r t t t r ~ . t t ~ t r Forsk

A. ~?ficit~~r/r . \ 1.

Hrr~gllwr(r C : I , / I I I L J ~ I L . ~ I W & A

('erio/~.s / L I ~ L I / !'err

Ikrrt.s l r ! f f ) l r~r~~z Lour

Ikoec.ctrrtr tr~~zlloclz~r L

I<. iirrdur Willd

&ntdt,litr c.lot~/~,/ I .

Acanthaceae

Pteridaceae

Myrsinaceae

Avicenniaceae

Avicenniaceae

Rhizophoraceae

Rhizophoraceae

Rhizophoraceae

Rhizophoraceae

Rhizophoraceae

Papilionaceae

Euphorbiaceae

Euphorbiaceae

Rhizophoraceae

Combretaceae

True mangrove species Family

Rhrzophorti apicrilutu Blume Rhizophoraceae

R. mr~c.rorttr(cr Lamk Rhizophoraceae

Sotfnerotlci casenlciris L. Sonneratiaceae

Semi mangrove species

( ~ i e . ~ c ~ / p ~ ~ r i ~ r cr~.s~ci L. Caesalpinaceae

( 'u lo / )h~~/ I~rm i~to~j)hvllitni L. Guttiferaceae

( i~ hrrt rdo/lrmt Gaenn. Apocynaceae

( ' lerode~~dr~tni rrrertiie Gaertn Verbenaceae

( :\r)rt~.! ~r/o/~c,~~irro~de.\ Rottb Cyperaceae

( ;trr7urt~cr~.\ Hoult Cyperaceae

I)ol~ch~itrdt-ot~e .spa/hncm L. Bignoniaceae

Ht,ririt*nr 11~ro~reili.s Drvand. Sterculiaceae

HI~I.SL~II.\ II/ICIC.YOII.S 1. llalvaceae

7hespe.~1~1 O O / ) I I / I I ~ ~ I Ca\,. Malvaceae

-- --

+ + + Verv common y Rare

+ + Common y Very rare

+ Occasional -- Yot found

Travancore Coast

Mslabar Coast

In Kerala for urbanisation, construction of harbours, ports, prawn farming,

coconut plantat~on and I-ice cultivation, vast mangal lands were cleared or reclaimed

(Silas, 1987. Anonymous, 1992) Extensive mangrove clearing occurred in Kerala due

to the population pressure (Mastaller, 1996). The Mangalavanam and Kumarakom

mangroves are declared as bird sanctuaries (Thomas and Fernandez, 1994).

Status of 3langroves in Cochiri

Studies of Kurian (1980) revealed the occurrence of small patches of

Acutr/hrr.> 11icifi)lrri.s L., Avicetitricr nlhtr Blume., Rhlhi,-ophoro sp., and Hrrrg~tIera sp. in the

Cochin rezlon of the Vembanad estuary. Rajagopalan el ol. (1986) in an appraisal of the

mangrove ecosvstem in Cochin backwater, suggested that, they are formative mostly

developing con small reclaimed or natural islands with the dominant vegetation

constituted b~ species of Acnrtth~t.s, I.~xcwcuria. Clerc~derrdro~r. Ac~iceras. A\~iceruri~r and

Wli,-ophorcr Muralidharan (1984) found that, moderate soil salinities, tidal inundation,

low redox potential and fine gained soil with its silt and clay were found to be

favourable k)r the colonization of Actrnrhrts ilIc~fc~Iiir.s L. in Cochin area. Jose (1989)

estimated the total litter production from Hr~tgrrirru sps. dominated ecosystem at Cochin

to be 70 .;0 tonnes/hdyear. Kadhakrishnan (1992) described the distribution and

abundance of the mangrove microflora in and around Cochin. Rajagopalan (1985) studied

the biotic and abiotic factors ol'the mangrove ecosystem in, the Vembanad lake, Cochin.

In Cochin the mangrove islands are increasingly threatened by the

population pressure and aquaculture operations (Thomas and Fernandez, 1994). Formerly

thriving shrimp production of Cochin backwaters have fallen almost to nil as the after

effects 01' e\tensive mangrobe clearance (Mastaller, 1996) Due to immense biotic

interference and nlultiple uses of mangrove vegetation, this resource is threatened with

great destruction So there is an urgent need to restore degraded mangrove ecosystems for

economic. social and sustainabilii y reasons. However very little studies have been carried

out on the physico-chemical conditions and the distribution pattern of mangrove flora of

Cochin

The present investigation was carried out on mangrove distribution and

physiological changes of mangroves of Cochin under varying hydrological conditions for

a period of 3 years ( 1996 to 1999)

The main objectives of this investigation were the following.

( 1 ) To study the present status of mangrove vegetation and to prepare a map of

the mangrove vegetation in Cochin

(2) To study the relatior~ship of water, soil texture and soil chemistry on the

distribution of mangrove species.

( 3 ) To study the physiology of mangrove species in relation to their distribution

patterri

(4) TO suggest methods for the management of mangroves of Cochin.

I'his thesis comprises of seven chapters and a common reference and an

appendix. Each chapter has a separate Introduction, Materials and Methods, Results and

Discussion