Crop yields will decrease substantially posing danger to food security
Degradation of soil and water resources is one of the major challenges for global agriculture. Climate change will further alter agricultural systems with substantial consequences for food production. The risk of reduced food yields is greatest in developing countries, where 790 million people are estimated to be undernourished at present.
In India, it is currently predicted that while overall rainfall may not experience a significant change, the temporal and spatial distribution may change. Central and northern parts of India may get less rainfall while the south-western parts may receive more. Irrigation will suffer if rainfall drops.
l According to the International Institute for Applied Systems Analysis (iiasa), Austria, India stands to lose 125 million tonnes (or 18 per cent) of its rain fed cereal production potential . If agricultural production goes down, the price of staple food commodities will increase (see table : Plummeting production).
l According to a study by the World Bank, a 2 c rise in temperature along with a seven per cent increase in rainfall will reduce net agricultural revenues by 12.3 per cent for the whole country .
l Agriculture in the coastal regions of Gujarat, Maharashtra and Karnataka will be the most negatively affected.
l An increase in winter temperature by 0.5 c will result in a 10 per cent reduction in wheat yield in the high yield states like Punjab, Haryana and Uttar Pradesh.
l An increase in minimum temperature from 18 c to 19 c will result in a decrease in rice yield of 0.71 tonne per ha, while an increase from 22 c to 23 c will result in a decrease of 0.41 tonne per ha.
l Even if there is some farm level adaptation, such as the enhanced use of fertilisers and use of different seeds, the loss in farm level net revenue will range from 9-25 per cent for a rise of 2-3.5 c .
l According to Lal, there will be some positive effects of climate change due to increase in carbon dioxide in the atmosphere resulting in what is known as "carbon dioxide fertilisation". For example, Madhya Pradesh produces 72 per cent of soybean grown in India with 77 per cent of its area devoted to soybean farming. According to some simulations, a 50 per cent increase in soybean yield could be obtained if atmospheric carbon dioxide concentration doubles. But temperature increase limits this gain; a rise of 1 c in minimum temperature with doubled carbon dioxide concentration limits the yield increase to 48 per cent. It was found that the positive effects of elevated carbon dioxide almost cancel out with enhanced thermal stress. Deficient monsoon rainfall conditions combined with thermal stress will adversely affect the positive effect of elevated carbon dioxide on the soybean crop in Madhya Pradesh.
l Moreover, studies using models that project an increase in crop yields due to carbon dioxide fertilisation are done with the assumption that carbon is a limiting factor in crop growth. This is not the case in India as other nutrients and water may impose more serious restraints.
l The maximum yield for both rice and wheat are obtained at surface temperatures of 1 c below the present day climate at current carbon dioxide levels. The yields decline more sharply for a rise in temperature. A 3 c rise in air temperature almost cancels out the positive effect of elevated carbon dioxide on wheat and rice yields.
l Climate change will cause a significant increase in pest populations , since generally warmer and moist conditions with longer freeze free periods are highly conducive to them.
l Reduction in soil moisture due to higher rates of evaporation will be an important stress factor for plants.
l Changes in forests will alter the configuration and productivity of forests ecosystems. These changes will affect traditional livelihoods, industry, biodiversity, soil and water resources and therefore, agricultural productivity .
l Under some climate change models, soil moisture is likely to decline and in turn, reduce forest productivity. For example, teak productivity will decline from 5.40 cubic metre per ha to 5.07 cubic metre per ha. The productivity of moist deciduous forests could decline from 1.8 cubic metre per ha to 1.5 cubic metre per ha.
Decline in crop production in India, according to different climate change models (in per cent)
of Space Studies
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