Rice Yields May Dip 6.6% for Global Temperature

India could lose 6.6 per cent of its rice yield for every 1 degree Celsius (°C) rise in global mean temperature, according to a new study. The estimate is more than three times higher than earlier projections. Rice is the staple food for about two-thirds of the country’s population. The study, published in the journal Science Advances, quantified the effects of global warming on rice production. Led by the Helmholtz Centre for Environmental Research, with contributions from the Potsdam Institute for Climate Impact Research, it compared real-world field-warming observations from 214 sites across rice-growing regions with seven crop models. Its findings suggest that rice yield losses caused by extreme heat may be much higher than previously understood. Modelled estimates for rice yield reductions from 1°C of global warming were roughly half those observed in realworld experiments, “3.8 per cent instead of 8.1 per cent. A study found that exposure to temperatures above 30°C was the prime reason of rice yield losses linked to warming. “At more than 70 percent of observed sites, high-temperature exposure accounted for more than half of absolute yield change. It also updated region-wise estimates of rice yield loss due to global warming. The steepest losses were projected in South and Southeast Asia. “For Pakistan, India and Bangladesh, the yield-loss estimate increases from 2.1 to 6.6 per cent. For Thailand, the Philippines and Myanmar, it increases from 3.7 to 7.7 per cent. The gap between observations and models appeared to be because many current crop models do not adequately capture heat damage during rice’s reproductive stages, lead author of the study from the Helmholtz Centre for Environmental Research. “Observations in the study show this is exactly when rice is particularly vulnerable to extreme heat, as panicles and grains develop. The findings add to growing concern over the impact of rising temperatures on food production. In March, a global analysis published in the journal Nature Food warned that at least half of crop production in low-latitude regions could be at risk as global warming crosses the 1.5°C threshold and climate conditions become increasingly unsuitable for food production. That study also warned of threats to crop diversity, projecting a decline across 52 per cent of global cropland if warming exceeds 2°C and 56 per cent if warming exceeds 3°C. For India, the latest research is another warning sign. In recent years, high-heat days have been widely reported to cause crop wilting, particularly in wheat and rice. In May, a study titled Climate Change and Crop Yields in India, based on data from 1966 to 2016, found that 1°C of warming reduced the national average yield across all crops by about 8 per cent. Heat and rainfall shocks had large and persistent effects on agricultural productivity, with some crops suffering much steeper losses than the national average. Pearl millet yields declined by as much as 19 per cent under a 1°C rise in temperature, while maize yields fell by more than 16 per cent, the data showed. In the worstaffected districts, yields could fall by as much as 39 per cent