(Dr. krishan Bir Chaudhary, President, Bharatiya Krishak Samaj)
July 28, 2010- New Delhi
Climate change is a reality and the main cause of the present situation is on account of the anthropogenic activities disturbing the composition of the atmosphere resulting in higher concentration of Carbon Dioxide (CO2) which accumulates along with other green house gases (GHG) like methane and nitrous oxide and contribute to increase in surface temperature of the earth. The main contributors have been the developed countries like US and EU but now other developing countries like China are slowly replacing as the main polluters. However, the per capita emission reveals that the main emitters are the developed countries. If the pace of this emission moves then it is expected the CO2 concentration which is currently less than 400 parts per million might shoot above 800 if high emission continues by the end of this century.
Table 1 Global CO2 emission and the country share
Source: World Development Indicators 2010.
The consequences of these emissions are already visible with disturbance in climate which in turn is touching everyone’s life. Climate is an important factor of agricultural productivity. Climate change is likely to impact agriculture and food security across the globe. A large fraction of the world's food including India is grown as rainfed annual crops (India’s irrigated share is 44%), and climate variability plays an important role in determining productivity. India faces a severe situation in the context that the population is increasing faster than the food grain yield and this could make the food and other agricultural product supply erratic and unpredictable. Another serious challenge confronting the agriculture is the competition for water resources increases, and the frequency of extreme temperatures changes. Globally, all societies will be vulnerable to changes in food production, quality and supply under climate change along with their consequent socio-economic pressures. Climate change is also expected to affect agricultural and livestock production, hydrologic balances, input supplies and other components of agricultural systems. Climate change is caused by the release of green house gases in the atmosphere. These green house gases accumulate in the atmosphere which results in global warming. The greenhouse gases, on one hand, allow the transmission of light reaching the earth, and on the other hand block the transmission of heat (infra-red radiation) trying to escape from the atmosphere, thus trapping the heat as in a ‘greenhouse’. The major changes observed as a result of global warming are changes in global climate change related parameters such as temperature, precipitation, soil moisture and sea level.
Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades and its projected continuation into the future. The decade of 2001-2009 was the warmest decade recorded on earth. Global average near-surface atmospheric temperature rose 0.6 ± 0.2° Celsius (1.1 ± 0.4°Fahrenheit) in the 20th century. Most scientists are of the opinion that most of the warming observed over the last 50 years is attributable to human activities. The main cause of the human-induced component of warming is the increased atmospheric concentration of greenhouse gases (GHGs) such as carbon dioxide (CO2), which leads to warming of the surface and lower atmosphere by increasing the greenhouse effect. Greenhouse gases are released by activities such as the burning of fossil fuels, land clearing, and agriculture. The contribution of different sectors to the global warming or CO2 emission are illustrated in Fig 1.
Fig 1 Contribution in CO2 Emission sectorwise
Source World Development Report 2010
An increase in global temperatures can in turn cause other changes, including a rising sea level and changes in the amount and pattern of precipitation. These changes may increase the frequency and intensity of extreme weather events, such as floods, droughts, heat waves, hurricanes, and tornados. Other consequences include higher or lower agricultural yields, glacier retreat, reduced summer stream flows, species extinctions and increases in the ranges of disease vectors. Warming is expected to affect the number and magnitude of these events.
Carbon Dioxide (CO2) and Methane (CH4) are the main greenhouse gases (GHG) contributing to global warming. Over the last century the earth has warmed approximately 1 degree Fahrenheit. The concentration of carbon dioxide in the atmosphere has risen from 290ppm (parts per million) in 1900 to nearly 400ppm. Industry, Electric Power Generation, Agriculture and Transportation are the four top sources of greenhouse gases.
It is being anticipated that the rising levels of greenhouse gases are likely to increase the global average surface temperature by 1.5-4.5oC over the next 100 years, raise sea-levels (thus inundating farmland and making coastal groundwater saltier), amplify extreme weather events such as storms and hot spells, shift climate zones towards poles, and reduce soil moisture.
2. AGRICULTURE AND CLIMATE CHANGE
Indian economy from times immemorial has been dependent on Monsoon which brings relief not just to the food security but to the whole economy. Rising temperatures and changes in rainfall patterns have direct effects on crop yields, as well as indirect effects through changes in irrigation water availability. Recent studies including IFPRI have shown that the rain fed yield changes are driven by both precipitation and temperature changes; the irrigated yield effects are from temperature changes alone. The results of the research suggest that in developing countries, yield declines predominate for most crops. Irrigated wheat and irrigated rice are especially hard hit. On an average, yields in developed countries are affected less than those in developing countries. For a few crops, climate change actually increases yields in the developed-country. In the East Asia and Pacific region, some crops fare reasonably well because higher future temperatures are favourable in locations where current temperatures are at the low end of the crop’s optimal temperature. South Asia is particularly hard hit by climate change. For almost all crops, it is the region with the greatest yield decline. Rainfed maize and irrigated and rainfed wheat still see substantial areas of reduced yields. Sub-Saharan Africa sees mixed results, with small declines or increases in maize yields and large negative effects on rainfed wheat. The Latin America and Caribbean region also has mixed yield effects, with some crops up slightly and some down.
A. AGRICULTURE AND CO2 LEVEL INCREASE
Some of the impacts of climate change on atmospheric composition include CO2 enrichment, increased levels of surface ozone and rising mean temperatures. Plants, through the process of photosynthesis, utilize the energy of sunlight to convert water from the soil and carbon dioxide from the air into sugar, starches, and cellulose. CO2 enters a plant through its leaves. Greater atmospheric concentrations tend to increase the difference in partial pressure between the air outside and inside the plant leaves, and as a result more CO2 is absorbed and converted to carbohydrates. Crop species vary in their response to CO2. Wheat, rice, and soybeans belong to a physiological class (called C3 plants) that responds readily to increased CO2 levels. Corn, sorghum, sugarcane, and millet are C4 plants that follow a different pathway. Higher levels of atmospheric CO2 also induce plants to close the small leaf openings known as stomata through which CO2 is absorbed and water vapour is released. Thus, under CO2 enrichment crops may use less water even while they produce more carbohydrates. This dual effect will likely improve water-use efficiency, which is the ratio between crop biomass and the amount of water consumed. The positive impacts of CO2 enrichment would, to some extent, compensate for the negative impacts of rising mean temperatures (which shorten the growing season of most annual crops, and so reduce yields of current varieties). The possible decline in air quality with increased levels of surface ozone could have serious detrimental effects on crop growth. This positive impact is indicative that agriculture will in many ways help in preserving and combating climate change by adapting to the current stress and help in conserving water. However, the impact is possible in the context of natural farming wherein less Carbon intensive agriculture is used. There is greater need to pursue a natural farming with more in situ (or in farm input resources which would reduce the cost of cultivation as well as help in mitigation).
B. HIGH TEMPERATURE IMPACT ON CROPS
In middle and higher latitudes, global warming will extend the length of the potential growing season, allowing earlier planting of crops in the spring, earlier maturation and harvesting, and the possibility of completing two or more cropping cycles during the same season. Many crops have become adapted to the growing-season day lengths of the middle and lower latitudes and may not respond well to the much longer days of the high latitude summers. In warmer, lower latitude regions, increased temperatures may accelerate the rate at which plants release CO2 in the process of respiration, resulting in less than optimal conditions for net growth. When temperatures exceed the optimal for biological processes, crops often respond negatively with a steep drop in net growth and yield. If night time temperature minimum rise more than daytime maximum, as is expected from greenhouse warming projections, heat stress during the day may be less severe than otherwise, but increased night time respiration may also reduce potential yields. Another important effect of high temperature is accelerated physiological development, resulting in hastened maturation and reduced yield.
C. AGRICULTURE AND MOISTURE STRESS
Climate change has a direct impact on water availability for irrigated crops. Internal renewable water (IRW) is the water available from precipitation. Though most of the global regions experience increased IRW, the Middle East and North Africa and Sub-Saharan Africa regions both experience reductions of IRW. In addition to precipitation changes, climate change-induced higher temperatures increase the water requirements of crops. The ratio of water consumption to requirements is called irrigation water supply reliability (IWSR). The smaller the ratio, the greater the water stress on irrigated crop yields. IWSR improves slightly for the Latin America and Caribbean region and for the Middle East and North Africa, but worsens slightly for Sub-Saharan Africa.
The availability of water for agriculture will be a key issue for crop production in the coming decades. There is a focus worldwide on how to improve the efficiency of water use for crop production. Higher CO2 levels improve the water usage efficiency of most crops. Plant transpiration is reduced under higher CO2 levels and the crop looses less water. Reduced transpiration over a sufficiently large region could lead to reduced precipitation there as well. These changes in transpiration can alter the hydrological balance over land and affect the local climate. This highlights the inherent links between crops, climate and the water cycle. Climate change will modify rainfall, evaporation, runoff, and soil moisture storage. Changes in total seasonal precipitation or in its pattern of variability are both important. The occurrence of moisture stress during flowering, pollination, and grain-filling is harmful to most crops and particularly so to corn, soybeans, and wheat. Increased evaporation from the soil and accelerated transpiration in the plants themselves will cause moisture stress; as a result there will be a need to develop crop varieties with greater drought tolerance. The demand for water for irrigation is projected to rise in a warmer climate, bringing increased competition between agriculture, urban as well as industrial users. Falling water tables and the resulting increase in the energy needed to pump water will make the practice of irrigation more expensive, particularly when with drier conditions more water will be required per acre. Peak irrigation demands are also predicted to rise due to more severe heat waves. Additional investment for dams, reservoirs, canals, wells, pumps, and piping may be needed to develop irrigation networks in new locations. Finally, intensified evaporation will increase the hazard of salt accumulation in the soil.
D. EXTREME CLIMATE AND AGRICULTURE
Important climate thresholds for food crops include episodes of high temperatures that coincide with critical phases of the crop cycle. These high-temperature episodes can lead to dramatic reductions in yield, in some cases in excess of 50%; for example, temperatures greater than 30°C lasting for more than 8 hours lead to reduced grain-set in wheat. Climate change scenarios suggest that critical temperature thresholds for food crops will be exceeded with increasing frequency in the future. For some crops, these critical temperatures, particularly at flowering and fruit or grain bearing, are reasonably well known (e.g. temperatures greater than 35 °C for more than 1 hour leads to pollen sterility in rice).
E. CLIMATE CHANGE AND QUALITY DEPRECIATION
Food systems can be vulnerable to climate change. Grain quality of wheat (e.g. protein content) is highly susceptible to current variations in climate and affects the type of foods that can be produced through, for example, gluten levels and related dough strength will affect crop storage and thereby increase the cost of transportation and storage. Other impact on crop quality include, pests and diseases, such as dangerous levels of mycotoxin contamination of groundnuts. Vegetable and fruits dehydrate and get contaminated besides losing texture and human find it difficult to consume.
F. CLIMATE CHANGE AND SOIL FERTILITY
Higher air temperatures will also affect the soil, where warmer conditions are likely to speed the natural decomposition of organic matter and to increase the rates of other soil processes that affect fertility. With dryer condition lesser water the decomposition will make available NPK for the plants to grow. This would also enhance the depletion of micronutrients and it availability and reduce the quality of produce from the land. Additional application of fertilizer may be needed to counteract these processes and to take advantage of the potential for enhanced crop growth that can result from increased atmospheric CO2. However, of adequate irrigation not provided the application of fertilizer will serve no purpose. Further excess application of fertiliser to overcome stress would pose a severe cost to environment impact water and air quality besides contamination of food chain. The continual cycling of plant nutrients (carbon, nitrogen, phosphorus, potassium, and sulphur) in the soil-plant-atmosphere system is also likely to accelerate in warmer conditions, enhancing CO2 and N2O greenhouse gas emissions.
G. CLIMATE CHANGE AND PEST AND DISEASES
Severe stress in climate with erratic rainfalls helps proliferation of insect pests in warmer climates. Longer growing seasons will enable insects such as grasshoppers to complete a greater number of reproductive cycles during the spring, summer, and autumn. Warmer winter temperatures may also allow larvae to winter-over in areas where they are now limited by cold, thus causing greater infestation during the following crop season. Altered wind patterns may change the spread of both wind-borne pests and of the bacteria and fungi that are the agents of crop disease. Crop-pest interactions may shift as the timing of development stages in both hosts and pests is altered. Livestock diseases may be similarly affected. The possible increases in pest infestations may bring about greater use of chemical pesticides to control them, a situation that will require further development and application of integrated pest management techniques.
H. CLIMATE CHANGE AND AGRICULTURE IN LOW LYING AREAS
Global warming is predicted to lead to thermal expansion of sea water, along with partial melting of land-based glaciers and sea-ice, resulting in a rise of sea level which may range from 0.1 to 0.5 meters (4 to 20 inches) by the middle of the next century, according to present estimates of the Intergovernmental Panel on Climate Change (IPCC). Such a rise could pose a threat to agriculture in low-lying coastal areas, where impeded drainage of surface water and of groundwater, as well as intrusion of sea water into estuaries and aquifers, might take place. In parts of Egypt, Bangladesh, Indonesia, China, the Netherlands, Florida, and other low-lying coastal areas already suffering from poor drainage, agriculture is likely to become increasingly difficult to sustain besides degradation of soil on account of salt intrusion. Island states are particularly at risk wiping off inhabitation and causing large scale immigration and other social problems.
I. CLIMATE CHANGE AND MONSOON IMPACT
ENSO (El Niño Southern Oscillation) is the most important factor contributing to water recharge in rainfed regions of India climate change warming in the ocean disturbs the pressure zones thereby disturbing the monsoon. Rice cultivation would be worst affected with a disturbed monsoon and unpredictable weather. Scheduled planting and harvesting based on weather patterns will become less effective. Even regions adjoining India like Indonesia where the main crop consists of rice will be more vulnerable to the increased intensity of ENSO effects in the future of climate change. Normal planting of rice crops begin in October and harvested by January. However, as climate change affects ENSO and consequently delays planting, harvesting will be late and in drier conditions, resulting in less potential yields.
3. CLIMATE CHANGE AND INDIAN AGRICULTURE
Agriculture and allied sector still constitutes the single largest component of around 17% of the Gross Domestic Product and providing an employment of around two thirds of the total work force. Its contribution to exports is close to 11 percentage and its intricate linkage with food prices makes it critical to providing not just the food needs of the country but also its neighboring South Asia region. At the country level the agriculture contributes 28 percentages of total GHG emissions. This share in agriculture does not include the fuel used in agriculture for energy use. The main GHG emission in agriculture comes from enteric fermentation which forms close to 60 percentages followed by methane emission from rice cultivation close to 23 percentages.
Fig 2 Sector wise GHG emission in Agriculture in India
Fig 3 Desegregation of the GHG Agricultural Emission in India
Source: India’s Initial National Communication on Climate Change, 2004
The impact of climate change on India agriculture has received very less attention in terms of policy mainly on account of differences emerging in the quantification of the effect arising from the change in temperature and build up of CO2 concentration. Even the methane emission from rice has received sharp criticism wherein western media reports of high methane emission have been proved erroneous (Box1). Notwithstanding this difference there is no denying that temperature has changed significantly in the country. Recent reports from different studies show that the surface temperature across the country is increasing. The global increase over the period of 100 years was close to 0.85oC and for India it was close to 0.54oC.
Source : ICAR
This increase in temperature is cause of alarm with the level of industrialization and growth model that is being pursued. The increase in temperature is a result of the buildup of the GHG emission accumulating in the region. This is and will result in more frequent hot days, hot nights and heat waves. This will also result in erratic precipitation and rise in sea level and low lying agriculture will be seriously affected. Even the tropical cyclones in the Bay of Bengal is set to increase and the glaciers in the Himalayas are going to contract flooding the perennial rivers like Ganga, Yamuna and Brahmaputra’s.
More specifically the clear impact of climate change is the increase in vulnerability of the crops, livestock, plantation crops, fisheries, soil fertility and water balance. This in turn will make the ecology unstable. Agriculture cultivation is a natural carbon sink wherein plants absorb CO2 and naturally sequester the Carbon from the atmosphere contributing to natural mitigation. An increase in CO2 to a level of 550 parts per million (ppm) increase the yields of rice, wheat, legumes and oilseeds by 10-20 percentage. However an increase of 1o C in temperature reduce yields of wheat, soybean, mustard, groundnut and potato by 3-7%. Reports indicate that the productivity of most crops decrease marginally by 2020 but by 10-40% by 2100. The variation in temperature will also affect yields of apples (including ripening), coconuts and all fruits and vegetables.
On account of increase in temperature water balance is going to get disturbed. Already the level of water exploitation is very bad and with increase in surface temperature and without adaptation it is anticipated the water bodies like the lakes, ponds are going to disappear on account of the heat. Already on account of unscrupulous exploitation fertile lands with rich biomass is being converted to industrial and residential and commercial purpose which is depleting the natural carbon sinks contributing to further build up of Green House Gases (GHG).
Industrialized agriculture in developed countries contribute more intensively to the buildup of CO2 than the subsistence and traditional agriculture practiced in developing countries. Similarly on meeting the growing demand commercial cultivation in Indian farm using synthetic fertilizer and chemicals is further adding to the GHG emission and degrading the fertility and productivity of Indian agriculture.
The new farming policies using Genetically Modified (GM) seeds is posing a serious threat since these crops use more water and synthetic fertilizers and chemicals which add to the carbon foot-prints and further aggravate climate change. These crops also reduce the biomass and biodiversity of the region and pose a threat and extinction of traditional crops and varieties.
(Bharatiya Krishak Samaj Concept Paper)