As climate change makes the tropical wheat environment less favourable and challenges the sustainability of wheat yields, global efforts are under way to develop new varieties of wheat which can withstand excessive heat and continue to retain their productivity levels. US-based International Maize and Wheat Improvement Center (CIMMYT), Cereal System Initiative in South Asia (CSISA)?a collaborative project led by the International Rice Research Institute and funded by the United States Agency for International Development and the Bill & Melinda Gates Foundation?and the International Centre for Agricultural Research in Dry Areas are developing new varieties suited to warmer, drier environments and promoting resource-conserving farming practices.
Scientists at CIMMYT have been preparing for heat-stressed areas for several years, and these resources can now be used in new heat-stressed regions, according to a report by the Consultative Group on International Agricultural Research (CGIAR). However, regions which are already hot and dry will require tougher varieties.
Wheat is planted across 240 million hectare worldwide. It is estimated that excess heat would hurt wheat yields spread across more than 9 million hectare globally, especially in the Indo-Gangetic plains covering India, Pakistan, Bangladesh and Nepal. ?This number will increase, as the Intergovernmental Panel on Climate Change predicts that global temperatures will rise by 1.8?C to 4.0?C by the end of the century. Current heat-stressed areas, which include some of the world?s poorest regions, are likely to suffer yield losses?, the CGIAR report says.
Union minister of state for agriculture, KV Thomas, speaking at a Ficci seminar, said the ?uncertainties of the changing climate are major challenges to agriculture in India and other developing countries?. Studies by agricultural scientist MS Swaminathan have estimated that a 0.50 degree increase in temperature could reduce the yield of wheat by 10% in states like Punjab, Haryana and Uttar Pradesh. Other studies estimate that the loss in farm-level net revenue may range from 9% to 25% for a temperature rise of 2 to 3.5 degrees.
?In order to maintain food security, we have to increase the yield potential of staple crops by 1.5% to 2% a year,? says Matthew Reynolds, a wheat pathologist at CIMMYT, adding that crop productivity is currently increasing annually by around 1%. ?Climate change reduces yield potential, so not only do we have to go from less than 1% to at least 1.5%, climate change is also making this target more difficult to achieve.?
The CGIAR report also adds that the Indo-Gangetic plains will be among the areas hardest hit by warmer temperatures, water scarcity and heightened soil salinisation. ?India, Pakistan, Nepal and Bangladesh, a productive wheat-growing area, is home to more than 1.2 billion people, many of whom are farmers growing annual rotations of rice and wheat. By 2050, over half the region is expected to suffer from heat stress and possible desertification. If wheat yields fall as a result, the situation will turn worse for the region?s 480 million poverty-stricken people?.
Quoting a CIMMYT publication, ?Wheat Facts and Futures?, the CGIAR report says, ?Climate change brings more than heat and drought. Variation in precipitation patterns will likely dry out some places while flooding others. Hotter and more humid conditions will encourage pests, diseases and weeds. In the tropics, heat is expected to shorten the grain-filling period for wheat, thus damaging product quality?.
However, there is good news as well. As some areas become hostile to wheat, others will become more receptive, such as the high latitudes, where a temperature increase of a few degrees is expected to boost wheat yields. Cool, high-latitude spring wheat environments, like the ones in Canada and Siberia, will benefit most, as farmers will be able to plant earlier and replace current cultivars with high-yielding winter wheat varieties, according to the report. Also, higher atmospheric carbon dioxide can enhance photosynthesis, which may boost plant growth and yields.