India could lose 6.6 per cent of its rice yield for every 1°C rise in global mean temperature, a new study estimates.
The estimate is more than three times higher than previous projections, raising concerns for a country where rice feeds about two-thirds of the population.
The study found that temperatures above 30°C are the main driver of warming-linked rice yield losses, especially during the crop’s reproductive stages.
South and Southeast Asia face some of the steepest projected losses because of high rice cultivation and growing exposure to extreme heat.
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 real-world experiments, “3.8 per cent instead of 8.1 per cent,” according to the study.
The 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,” the study said.
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,” according to the study.
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, said Yiwei Jian, 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,” Jian said.
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.
The study found that 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 worst-affected districts, yields could fall by as much as 39 per cent.