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“The past actions of mankind have changed the climate, and now the climate is affecting the actions of mankind. The chapters of this book do impart key information on many key aspects of the impact climate change is having and may/will have on agriculture. …Knowledge on this topic is changing rapidly and there are few overviews, except from governments and governmental groups. So, the content of the book is definitely relevant and useful.”—David Whitacre, Editor, Reviews of Environmental Contamination and Toxicology

Explore the Relationship between Crop and Climate

Agricultural sustainability has been gaining prominence in recent years and is now becoming the focal point of modern agriculture. Recognizing that crop production is very sensitive to climate change, Climate Change Effect on Crop Productivity explores this timely topic in-depth. Incorporating contributions by expert scientists, professors, and researchers from around the world, it emphasizes concerns about the current state of agriculture and of our environment. This text analyzes the global consequences to crop yields, production, and risk of hunger linking climate and socioeconomic scenarios.

Addresses Biotechnology, Climate Change, and Plant Productivity

The book contains 19 chapters covering issues such as CO2, ozone on plants, productivity fertilization effect, UV (ultraviolet) radiation, temperature, and stress on crop growth. The text discusses the impact of changing climate on agriculture, environment stress physiology, adaptation mechanism, climate change data of recent years, impact of global warming, and climate change on different crops. It explores the overall global picture in terms of the effect of crops to climate change during abiotic stress and considers strategies for offsetting and adapting to ongoing climate change.

An asset to agriculturists, environmentalists, climate change specialists, policy makers, and research scholars, Climate Change Effect on Crop Productivity provides relevant information and opportunities for productive engagement and discussion among government negotiators, experts, stakeholders, and others concerned about climate change and agriculture.

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Climate Change Effecton Crop Productivity

Edited byRakesh S. Sengar and Kalpana Sengar

Clim

ate C

hange Effe

cton

Crop

Productivity

R. SengarK. Sengar

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Climate Change Effecton Crop Productivity

Edited byRakesh S. Sengar and Kalpana Sengar

187

ChApteR eIGht

Global warming impact on rice crop productivity

D.P. Singh

Abstract

Rice is a major food crop of Asia and of the world. The impact of global warming on rice may be due to a rise in sea level, thus resulting in inundated lands with sea water which makes these lands unsuitable for rice cultivation. Climate change is estimated to affect 20 million hectares of the world’s rice-growing area adversely, mainly in India and Bangladesh. It is forecasted by the International Food Policy Research Institute that by 2050, the rice prices will increase between 32% and 37% as a result of climate change due to the reduction in rice productivity by 14% in South Asia, 10% in East Asia and the Pacific and 15% in sub-Saharan Africa. The rise in carbon dioxide levels in the environment may result in higher biomass in rice, which, depending on the type of cultivars, may or may not

Contents

Abstract 1878.1 Introduction 1888.2 Global warming 1888.3 Global warming and rice productivity 1898.4 Land and water resources for rice 1918.5 Salinity, flooding and rice 1938.6 Water shortage and rice productivity 1948.7 Global warming and its impact on pests, diseases

and weeds 1948.8 Strategies for mitigating effects of global

warming on rice production 195References 196

188 CLIMATE CHANGE EFFECT ON CROP PRODUCTIVITY

increase the grain yield. Climate change may be tackled by adopting proper strategies in research and policies of different countries. A proactive approach to this may save the rice production, as well as help in reducing emissions of greenhouse gas ‘methane’ from rice cultivation.

8.1 Introduction

The world population is growing steadily on the one hand, whereas land and water resources are declining on the other. Rice is the primary staple food for more than half the world’s population. Asia represents the largest producing and consum-ing region. A total of 651 million tonnes of rice (paddy) was harvested in Asia in 2012 (FAOSTAT, 2012). Rice production is rising in South Asia but falling in the east. It is also a staple food in sub-Saharan Africa, preferred in China and the only available domestic staple in many countries in Asia (FAOSTAT, 2010). An increase in rice production by ≈1% annually is estimated to meet the growing demand for food that will result from popu-lation growth and economic development (Rosegrant et  al., 1995). Global population is predicted to rise to over 9 billion by 2050, which will lead to a 25% increase in the demand for rice. Most of this increase must come from greater yields on existing cropland to avoid environmental degradation, destruc-tion of natural ecosystems and loss of biodiversity (Cassman, 1999; Tilman et al., 2002). During this period, a warmer climate may decrease rice yields by 8%. Fresh global water supply will be needed to accommodate increased rice production and an additional 57,280,000,000 L (1432 L × 40,000,000 kg) of fresh water will be required. Fresh water demands will be more in highly populated countries like India and China, which are the main producers of rice in the world.

8.2 Global warming

‘Global warming’ refers to the rise in the average temperature of the earth’s atmosphere and oceans. The greenhouse gases (carbon dioxide, water vapour, nitrous oxide and methane) trap heat and light from the sun in the Earth’s atmosphere and lead to an increase in the temperature. Huge quantities of green-house gases are released into the atmosphere due to mining and combustion of fossil fuels, deforestation and maintenance of livestock herds and also due to rice production. The increase in

189GLOBAL WARMING IMPACT ON RICE CROP PRODUCTIVITY

temperature harms people, animals and plants, including rice. The higher the concentration of greenhouse gases, the more the trapping of heat in the atmosphere and the reduced escape of heat back into space. The higher heat results in a change in cli-mate and altered weather patterns. In 2001, the ‘UN-sponsored Intergovernmental Panel on Climate Change’ reported that worldwide temperatures have increased by more than 0.6°C in the past century and estimated that by 2100, average tempera-tures will increase by between 1.4°C and 5.8°C (Nguyen, 2005).

8.3 Global warming and rice productivity

High temperatures or global warming would decrease the rice production globally (Furuya and Koyama, 2005). There is a need to plan for appropriate strategies to adapt to and miti-gate the global warming for achieving long-term food secu-rity. Both lowland rice cultivation and upland rice production under slash-and-burn shifting cultivation results in the emis-sion of methane and nitrous oxide gases and, thus, contributes to global warming. Increased concentration of carbon dioxide in the atmosphere along with rising temperatures are two major factors making rice agriculture a larger source of greenhouse gas ‘methane’ which may double by the end of this century. Methane is produced from carbon and hydrogen by bacteria in the soil. Some carbon enters the soil from the roots of rice plants, which have taken it from the atmosphere via photosyn-thesis. The rice plants grow faster under higher carbon dioxide concentration. This growth, in turn, pumps up the metabolism of methane-producing microorganisms in soil in rice field, thus generating more methane. Rice farming is responsible for approximately 10% of the methane released. Researchers at Northern Arizona University gathered published research from 63 different experiments on rice paddies, mostly from Asia and North America. The meta-analysis was used and found two strong patterns: first, more carbon dioxide boosted emissions of methane from rice paddies, and second, higher temperatures caused a decline in rice yields. According to the study, in the future the amount of methane emitted from rice paddies is likely to increase. Together, higher carbon dioxide concentra-tions and warmer temperatures predicted by the end of this cen-tury will double the amount of methane emitted per kilogram of rice produced (NAU, 2013). Since half of the worlds’ human population is highly dependent on rice, the production systems for this crop are, thus, vital for the reduction of hunger and

190 CLIMATE CHANGE EFFECT ON CROP PRODUCTIVITY

poverty. The cultivation of rice extends from dry lands to wet-lands and from the banks of the Amur River at 53° north latitude to Central Argentina at 40° south latitude. Rice is also grown in cool climates at altitudes of over 2600 m above sea level in the mountains of Nepal, as well as in the hot deserts of Egypt. However, most of the annual rice production comes from tropi-cal climate areas. In 2004, more than 75% of the global rice harvested area (about 114 million out of 153 million ha) came from the tropical region whose boundaries are formed by the Tropic of Cancer in the Northern Hemisphere and the Tropic of Capricorn in the Southern Hemisphere (Nguyen, 2005). The temperature increases, which results in rising seas and changes in rainfall patterns and distribution, and may affect the land and water resources required for rice production and achieving the desired productivity of rice crops. The highest limit of tempera-ture for growth of rice is 45°C and temperatures above this will be adverse for yields. The optimum temperature range for rice at different stages after germination is 35–31°C whereas for rip-ening it is 20–29°C (Table 8.1). The temperature may affect and produce abnormal symptoms in rice (Table 8.2). Such a rapid increase during the crop growth stages, particularly during extremely sensitive reproductive and early grain-filling stages of rice (Oryza sativa L.), leads to reduced biomass, grain yield and quality. Hence, increasing diurnal temperature tolerance in

table 8.1 Critical temperatures for the development of rice plant at different growth stages

Growth stages

Critical temperature (°C)

Low High Optimum

Germination 16–19 45 18–40Seedling emergence 12 35 25–30Rooting 16 35 25–28Leaf elongation 7–12 45 31Tillering 9–16 33 25–31Initiation of panicle primordia 15 − − Panicle differentiation 15–20 30 − Anthesis 22 35–36 30–33Ripening 12–18 >30 20–29

Source: From Yoshida, S. 1978. Tropical Climate and Its Influence on Rice. IRRI Research Paper Series 20. Los Baños, Philippines, IRRI.

191GLOBAL WARMING IMPACT ON RICE CROP PRODUCTIVITY

rice is a more sustainable approach than altering well-estab-lished cropping patterns, which will inevitably lead to yield penalties (Nagarajan et al., 2010). The current temperatures are already approaching critical levels during the susceptible stages of the rice plant, namely, Pakistan/North India (October), South India (April, August), East India/Bangladesh (March–June), Myanmar/Thailand/Laos/Cambodia (March–June), Vietnam (April/August), Philippines (April/June), Indonesia (August) and China (July/August) (Wassmann et al., 2009b).

8.4 Land and water resources for rice

The increase in temperature will create more land and water for growing rice in areas outside the tropical region (Darwin et al., 2005). The areas of coastal regions in the United States (Florida, much of Louisiana), the Nile Delta and Bangladesh will become unsuitable for rice with the rise of sea level by 88 cm (Kluger and Lemonick, 2001).

During the last two decades, night temperatures have increased at a much faster rate than day temperatures and global climate models predict a further increase in its frequency and intensity. The rice crop is affected both at the vegetative and reproductive stage due to a rise in temperature and, hence, pro-ductivity is also affected. The temperatures required at different crop growth phases are given in Table 8.1. High temperatures may result in various possible injuries to rice crops (Table 8.2). High temperatures for 1–2 h at anthesis may result in sterility of the rice crop. Mohandrass et al. (1995) predicted a decline in yield by 14.5% in summer rice in India by 2005 based on experiments at multi-locations. In the Philippines too, yields of dry-season rice declined by 10% for every 1°C increase in growing-season minimum temperatures, whereas the effect of

table 8.2 Symptoms of heat stress in rice

Growth stage Symptoms

Vegetative White leaf tip, chlorotic bands and blotches, white bands and specks, reduced tillering, reduced height

Reproductive anthesis Reduce spikelet number, sterilityRipening Reduced grain-filling

Source: From Yoshida, S. 1981. Fundamentals of Rice Crop Science. Los Baños, Philippines, IRRI. 269 pp.

192 CLIMATE CHANGE EFFECT ON CROP PRODUCTIVITY

maximum temperature on crop yields was insignificant. Peng et  al. (2004) provided evidence in support of statements that decreased rice yields from increased nighttime temperature was associated with global warming. Temperature and radiation had statistically significant impacts during both the vegetative and ripening phases of the rice plant. Welch et al. (2010) concluded that diurnal temperature variation must be considered when investigating the impacts of climate change on irrigated rice in Asia. Higher temperatures can adversely affect rice yields through two principal pathways, namely (i) high maximum temperatures that cause—in combination with high humid-ity—spikelet sterility and adversely affect grain quality, and (ii) increased nighttime temperatures that may reduce assimilate accumulation. On the other hand, some rice cultivars are grown in extremely hot environments, so that the development of rice germplasm with improved heat resistance can capture an enor-mous genetic pool for this trait. The results show that high night temperature compared with high day temperature reduced the final grain weight by a reduction in grain growth rate in the early or middle stages of grain filling, and also reduced cell size midway between the central point and the surface of the endo-sperm (Morita et al., 2005). In the Philippines, rice production may decline up to 75% by 2100 because of global warming and Filipinos will have to settle for meals with little or no rice unless the government aggressively implements climate change adaptation programmes (Antiporda, 2013). Transpiration from rice panicles can help lower the temperature of the panicle, which is the susceptive organ for high-temperature-induced spikelet sterility. By increasing the transpiration, the heat dam-age to the panicle predicted to occur due to global warming may be avoided. To examine the possibility of genetic improve-ment in transpiration conductance of intact rice panicles (gpI), we measured gpI at the time of flowering in the open field in 21 rice varieties of widely different origins. Thus, the target of improvement in gpI against high-temperature-induced spikelet sterility should be set at the level of the existing varieties with the highest gpI (Fukuoka et al., 2012). Tao et al. (2008) stud-ied the impact of global warming on rice production and water use in China, against a global mean temperature. They found the median values of rice yield decrease ranged from 6.1% to 18.6%, 13.5% to 31.9% and 23.6% to 40.2% for GMT changes of 1°C, 2°C and 3°C, respectively. Yoshimoto et al. (2010) synthe-sised a process-based model study in tandem with FACE exper-iments for studing the effects of climate change on rice yields in Japan. They found that it not only contributes to reducing

193GLOBAL WARMING IMPACT ON RICE CROP PRODUCTIVITY

the evaluation uncertainties, but also validates the adapting or avoiding studies of heat stress or negative influence on rice under projected climate change. The biomass production in rice will be more, which may or may not increase the grain yield. The higher temperatures can result in sterility in flowers, which will then adversely affect yields. The higher respiration losses due to a rise in temperature will also make rice less productive. IRRI research indicated that a rise in nighttime temperature by 1°C may result in losses in rice yields by about 10%.

8.5 Salinity, flooding and rice

Rice is highly sensitive to salinity. Salinity often coincides with other stresses in rice production, namely drought in inland areas or submergence in coastal areas. Submergent tolerance of rice plants has substantially been improved by introgressing the Sub1 gene into popular rice cultivars in many rice-growing areas in Asia. The rice crop has many unique features in terms of susceptibility and adaptation to climate change impacts due to its semi-aquatic phylogenetic origin. The bulk of global rice supply originates from irrigated systems, which are to some extent shielded from immediate drought effects. The buffer effect of irrigation against climate change impacts, however, will depend on the nature and state of the respective irrigation system (Wassmann et al., 2009b). Although rice can grow in water fields, submerged crops under water for long periods of time are not tolerated by rice plants. Flooding due to sea level rises in coastal areas and tropical storms will hinder rice pro-duction. At present, about 20 million hectares of the world’s rice-growing area is at risk of occasionally being flooded to submergence level in India and Bangladesh. Wassmann et al. (2009b) in his review paper mentioned that the mega-deltas in Vietnam, Myanmar and Bangladesh are the backbone of the rice economy in the respective country and will experience specific climate change impacts due to sea level rise. Significant improvements of the rice production systems, that is, higher resilience to flooding and salinity, are crucial for maintaining or even increasing yield levels in these very productive del-taic regions. The other ‘hotspot’ with especially high climate change risks in Asia is the Indo-Gangetic Plains (IGP), which will be affected by the melting of the Himalayan glaciers. The dominant land use type in the IGP is rice–wheat rotation. The geo-spatial vulnerability assessments may become cru-cial for planning targeted adaptation programmes, but policy

194 CLIMATE CHANGE EFFECT ON CROP PRODUCTIVITY

frameworks are needed for their implementation (Wassmann et al., 2009a).

8.6 Water shortage and rice productivity

Rice cultivation needs plenty of water. The changes in climate leading to a week without rain in upland rice-growing areas and 2 weeks in shallow lowland rice-growing areas can cause reduction in rice yields in the range of 17–40%. The intensity and frequency of droughts are predicted to increase in rain-fed rice-growing areas. Such changes are also expected in reduce water-short irrigated areas for rice cultivation. It affects rain-fed rice production in an area of 23 million hectares in South and Southeast Asia and about 20 million hectares of rain-fed lowland rice in Africa. The scarcity of water may also affect rice production in Australia, China, the United States and other countries. Drought stress is also expected to aggravate through climate change; a map superimposing the distribution of rain-fed rice and precipitation anomalies in Asia highlights espe-cially vulnerable areas in East India/Bangladesh and Myanmar/Thailand (Wassmann et al., 2009a,b).

8.7 Global warming and its impact on pests, diseases and weeds

The IRRI experiments over the last 10 years at farmers’ fields indicated that rice diseases and pests are influenced greatly by climate change. The incidence of diseases like brown spot and blast increases due to shortages of water, irregular rainfall pat-terns and related water stresses. On the other hand, the inci-dence of sheath blight or whorl maggots or cutworms reduces due to a change in the environmental conditions and shifts in production practices adopted by farmers to reduce the impact of climate change. It, thus, results in an emergence of new crop health dynamics. Global warming will enhance rice–weed com-petition. Rodent population outbreaks in Asia may increase due to unseasonal and asynchronous cropping as a result of extreme weather events. A combined simulation model (CERES-Rice coupled with BLASTSIM) was used to study the effects of global temperature change on rice leaf blast epidemics in sev-eral agro-ecological zones in Asia. At least 5 years of historical daily weather data were collected from each of 53 locations in five Asian countries (Japan, Korea, China, Thailand and

195GLOBAL WARMING IMPACT ON RICE CROP PRODUCTIVITY

Philippines). Two weather generators, WGEN and WMAK, from the Decision Support System for Agrotechnology Transfer, were utilised to produce estimated daily weather data for each location. Thirty years of daily weather data produced by one of the generators for each location were used as input to the com-bined model to simulate blast epidemics for each temperature change. Maximum blast severity and the area under the disease progress curve caused by leaf blast which resulted from 30-year simulations were statistically analysed for each temperature change and for each location. Simulations suggest that tempera-ture changes had significant effects on disease development at most locations. However, the effect varied in different agro-eco-logical zones. In the cool subtropics such as Japan and north-ern China, elevation of temperature above normal temperature resulted in more severe blast epidemics. In warm/cool humid subtropics, elevation of temperature caused significantly less blast epidemics. However, lower temperature caused insignifi-cant difference in disease epidemics compared with that in nor-mal temperature. Conditions in the humid tropics were opposite to those in cool areas, where daily temperature changes by −1°C and −3°C resulted in significantly more severe blast epidemics, and temperature changes by +1°C and +3°C caused less severe blast. Scenarios showing blast intensity affected by temperature change in different agro-ecological zones were generated with a geographic information system (GIS) (Luo et al., 1998).

8.8 Strategies for mitigating effects of global warming on rice production

The paddy experiments carried out at UC Davis and Trinity College Dublin indicated that increased carbon dioxide in the atmosphere boosted rice yields by 24.5% and methane emis-sions by 42.2%, increasing the amount of methane emitted per kilo of rice (Soos, 2012). There are several options available to reduce methane emissions from rice agriculture. The manage-ment practices such as mid-season drainage and using alterna-tive fertilisers as well as switching to more heat-tolerant rice varieties and adjusting sowing dates are some of the measures suggested to reduce the methane emissions (NAU, 2013).

The following are few of the strategies which may be adopted to counter the effect of global warming on rice:

1. To breed and release new rice cultivars with better adap-tation to high temperature and other climatic stresses

196 CLIMATE CHANGE EFFECT ON CROP PRODUCTIVITY

2. Develop new agro-ecosystem models which may be capable of predicting more correctly the consequences of climate change and land use change at different scales

3. Deployment of new management strategies for an eco-logical intensification of rice landscapes in Asia for increasing resource use efficiency, enhanced ecosystem resilience and a reduction in global warming potential

4. Create national and regional adaptation and mitigation policies for climate change on rice-based agriculture and net contributions of rice systems to global warming

References

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Cassman, K.G. 1999. Ecological intensification of cereal produc-tion systems: Yield potential, soil quality, and precision agricul-ture. Proc. Natl. Acad. Sci. USA 96: 5952–5959.

Darwin, R., Ts igas , M., Lewandrowski , J. and Raneses , A. 2005. World agriculture and climate change: Economic adaptation. USDA Agricultural Economic Report No. 703. 86 pp.

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Varietal range in transpiration conductance of flowering rice panicle and its impact on panicle temperature. Plant Prod. Sci. 15: 258–264.

Furuya, J . and Koyama, O. 2005. Impacts of climatic change on world agricultural product markets: Estimation of macro yield functions. JARQ 39: 121–134.

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Luo, Y. , Teng, P.S. , Fabellar, N.G. and TeBeest, D.O. 1998. The effects of global temperature change on rice leaf blast epidemics: A simulation study in three agroecological zones. Agriculture Ecosystems & Environment 68: 187–196.

Mohandrass, S. , Kareem, A.A. , Ranganathan, T.B. and Jeyaraman, S. 1995. Rice production in India under the current and future climate. In: Modeling the Impact of Climate Change on Rice Production in Asia, R.B. Mathews, M.J. Kroff, D. Bachelet and H.H. van Laar (eds), pp. 165–181. United Kingdom, CAB International.

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Nagarajan, S. , Jagadish, S.V.K. , Hari Prasad, A.S. , Thomar, A.K. , Anjali , A. , Madan P. and Agarwal, P.K. 2010. Local climate affects growth, yield and grain qual-ity of aromatic and non-aromatic rice in northwestern India. Agriculture, Ecosystems & Environment 138: 274–281.

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