Concerns of Indian Agriculture to Climate Change:
Authors: Shiv Kumar and Kanika

Climate change has a global concern because of its potential threats to sustainable economic development and agriculture is more sensitive to it. There is considerable regional variation in the climate and agricultural practices in India. Geography and location are thus important for climate as well as agriculture. Estimates provided herein of climatic effects for three homogeneous agro-climatic regions, viz. humid, semi-arid temperate, and arid-semi-arid tropical regions which have become very important. Information on estimation of climate impacts on gross revenue per hectare for different agro-ecological regions enables policy makers to take informed decisions on region-specific technological and policy options for enhancing resilience of agriculture.

India is quite heterogeneous in climate, agricultural practices and socio-economic characteristics; hence the climate impacts are likely to vary across agro-climatic regions. The information in this article is based on use of average annual temperature, annual rainfall and soil types for differentiating geographical units into homogeneous regions. A humid region is considered to have length of growing period exceeding 270 days. The semi-arid temperate region has length of growing period ranging between 70-180 days with daily mean temperature during the growing period being in the range of 5-20°C, and has have one or more months with mean temperature, corrected to sea level below 5°C. The semi-arid tropics are those regions where length of growing period is 70-180 days and all months have a mean monthly temperature greater than 18°C and daily mean temperature greater than 20°C during the growing period. Arid regions have length of growing period less than 75 days.

The consequences of climate change are likely to be more severe for rainfed, arid and semiarid regions because of their heavy dependence on agriculture, and lack of financial resources for mitigation and adaptation to climate change. Available evidence suggests reduction in agricultural productivity due to climate change in both developed and developing that a 1.0°C rise in mean temperature would reduce yields of wheat, soybean, mustard, groundnut and potato by 3.5-7.5 per cent. Furthermore, by 2039 if the mean temperature and precipitation increase by 0.5°C and 4 per cent respectively the loss in gross revenue per hectare will be in the range of 5 to 8.5 per cent. These evidences suggest that without mitigation and adaptation strategies climate change can have far-reaching consequences for the Indian agriculture and the farmers. Although, the share of agriculture in the gross domestic product is only about 15 per cent, it is an important source of livelihood for more than half of the country's population. Agriculture is dominated by small farms; more than 86 per cent landholdings are of size less than or equal to 2 hectares. Land is limited, and there is hardly any scope to bring additional land under agriculture. India's net cropped area has stagnated at around 140 million hectares. Ground water resources are widely used for agriculture, but are depleting fast. On the other hand, increasing population and sustained income growth have been putting pressure on agriculture to produce more per unit land so as to meet the growing demand for food and agricultural products.

Most studies on climate impacts on Indian agriculture have used net revenue per hectare as dependent variable and found rainfed crops are more sensitive to temperature as well as rainfall than are the irrigated crops. Irrigation indeed is important to mitigate harmful impacts of climate change (extreme temperatures and scanty rainfall). It can supplement or substitute for precipitation at critical growth stages of the crop.

Climate change in India
The mean normal temperature in the kharif season ranges from 27.5 to 29.7°C. This period covers sweltering summer months of June and July, and also receives most of the precipitation. The rabi season is somewhat cooler with mean normal temperature being in the range of 18.8° to 23.0°C. There are considerable regional differences in the annual precipitation, ranging from as high as 1661 mm in the humid region to 800 mm in the arid-semi-arid tropical region. It is observed an upward trend in the annual mean temperature at the national as well as regional level. At national level, the annual temperature during this period increased by 0.30°C. The rise in annual temperature has been relatively more in arid-semi-arid tropical region (0.34°C), and less in humid region (0.22°C). By crop season, rise in temperature is faster in rabi season (except in semi-arid temperate region) indicating that winters in India are becoming warmer.

As far rainfall is concerned it is observed a slight decrease in the quantum of annual rainfall at the national level; and this is caused mainly by a significant decline in the kharif rainfall (23 mm). The changes in seasonal rainfall vary across regions. Humid region has experienced a significant decrease in the kharif rainfall, but a significant increase in the rabi rainfall. In semi-arid temperate region there has been a significant decline in kharif rainfall, about 95 mm, more than in any other region. In arid-semi-arid tropical region no significant change is observed in kharif rainfall, but a significant decline in rabi rainfall. These findings indicate that although rainfall at national does not show any significant trend and seems random in nature, there are pockets of significant long-term changes in seasonal rainfall.

Impact of climate change on agriculture
Effects of change in annual temperature and rainfall on the gross revenue per hectare reveal that higher temperature reduces gross revenue per hectare; while higher rainfall has a positive effect. The damages due to higher temperature, however, are quite large -- a rise of 1°C in annual temperature reduces gross revenue per hectare by about 7.5 per cent. Effects of changes in seasonal climate deciphers that the rise in temperature in both the kharif and the rabi seasons has a negative effect on the gross revenue per hectare. The kharif temperature is 2.3 times stronger as compared to that of rabi temperature. This is almost equal to ratio of the output of kharif crops to the output of rabi crops in India, suggesting that temperature sensitivity of kharif and rabi crops on average is similar. On the other hand, rainfall in both kharif and rabi seasons has a positive and significant effect on agricultural productivity. The rabi rainfall, however, seems to have a larger effect. An excess rainfall has a damaging effect on the gross revenue per hectare. It further clarifies that effects of temperature and rainfall on productivity are not mutually exclusive i.e. are not independent of each other. Irrigation reduces harmful effects of temperature on agriculture. As the negative effect of temperature is larger in the kharif season, the effect of irrigation is also stronger in this season. Effects of climate change are unlikely to be uniform throughput; as expected, the effect of irrigation of gross revenue per hectare is favourable, but is more pronounced in the arid tropics, and the least in the intensively irrigated semi-arid temperate region

Marginal effects
Marginal effects of seasonal temperatures and rainfall at the national level matters a lot for Indian agriculture. Higher temperature in both kharif and rabi seasons reduces gross revenue per hectare. A 1°C rise in the rabi temperature reduces gross revenue per hectare by 4.20 per cent, and a similar increase in the kharif season reduces it by 5.5 per cent. Irrigation reduces harmful effects of warmer climate on the agricultural productivity by 20 per cent in the rabi season and 18 per cent in the kharif season. Note that, the effect of rainfall in either of the season is much smaller than the effect of temperature. This implies that Indian agriculture is likely to be influenced largely through changes in temperature.

Across agro-climatic zones, marginal effects of temperature and rainfall vary in their magnitude as well as direction. The arid and semi-arid tropical regions are most vulnerable to climate change. The marginal effect of temperature is negative in the rabi as well in the kharif season, but is more pronounced in the kharif season. A 1°C increase in the kharif temperature reduces gross revenue per hectare by 8.5 per cent, while in the rabi temperature its effect is not as severe. The damages due to rise in temperature, however, are partially offset by irrigation. For instance, a rise in rabi temperature in the semi-arid temperate region reduces gross revenue per hectare; the rise in kharif temperature tends to offset damages caused by the rabi temperature. Marginal effects of seasonal rainfall are significantly positive everywhere except in the rabi season in the humid region. Like temperature, the effects of rainfall are also stronger in the arid and semi-arid tropical regions.

In the short-run (next 25 years), agriculture is not much sensitive to the climate change. At national level, losses in gross revenue are small and almost similar (4-5%). However, with progression of time the losses in gross revenue per hectare become larger. In the medium-run (2040-69), losses rise between 8 to 14 per cent. Without adaptation (irrigation) losses would be even more.

The impact of climate change will not be uniform as expected. The arid and semi-arid tropics are very sensitive to climate change. The semi-arid temperate region, in contrast, will be the least impacted by the climate change because of better availability of irrigation that counterbalances adverse effects of rising temperature to an extent. The humid region is also not much impacted by climate change, as there is ample rainfall to counterbalance the adverse effects of rising temperature.

Marginal effects of climate variables show that higher temperature in kharif as well as rabi seasons has harmful effect on the gross revenue per hectare. Higher rainfall, unless it is in excess, has a beneficial effect on productivity, but the effect too small to offset negative effect of temperature, meaning that climate change in India overwhelmingly will affect agricultural productivity through rise in temperature. Irrigation, however, reduces harmful effects of higher temperature particularly in the rabi season in which rainfall is scanty.

In the short-run, impact of climate change will be mild. Reduction in gross revenue will be around 5 per cent. The consequence of climate change in the long-run will be severe depending on the level of changes in temperature and precipitation. Gross revenue per hectare may be 12 per cent less with moderate change in climate. The losses will be higher in absence of rapid adaptation. An important message from this study is that management of irrigation resources will be critical to enhance resilience of agriculture to climate change. About 80 per cent of the available water in the country is used to irrigate crops. Yet close to 60 per cent of the cropped area remains rainfed. However, 20-25 per cent of it can be brought under irrigation by harvesting, conserving and utilizing rainwater. Harnessing this potential will require capital investment to create on-farm structures. Groundwater in the intensively cultivated northwest region, has reached its limits of exploitation partly because of faulty policy of provision of free or subsidized electricity for agricultural purposes. Further, given scarcity of water it is imperative to bring about improvements in the water-use efficiency, through application of micro-irrigation technologies, e.g. sprinkler and drip irrigation. It may be noted that at present India has only 4 million hectares of area under micro-irrigation as against a potential of 40 million hectares. Another way to reduce adverse effects of climate change on agriculture and food security is through breeding of crop varieties that can tolerate or escape abiotic stresses such as droughts, floods, heat waves. A ray of hope lies in biotechnology that offers immense opportunities to move forward in this direction. The overall expected outcome for enhancing resilience of agricultural production to climate variability in vulnerable regions could be accomplished by demonstrating site specific technology packages on farmers' fields for adapting to current climate risks and capacity building of researchers and other stakeholders in climate resilient agricultural research and its application.

About Author / Additional Info:
Shiv Kumar -Senior Scientist (Agricultural Economics), National Centre for Agricultural Economics and Policy Research (Pusa), New Delhi.

Kanika - Senior Scientist (Plant Biotechnology), NRC Plant Biotechnology, IARI, Pusa, New Delhi-110012.