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Exposure to extreme heat is consistently and significantly reducing crop yield in Karnataka, according to a recent study. There are a significant number of extreme degree days (EDD) in a cropping season, when the daily temperature is above the critical threshold, suggested data analysed by experts from Tata Institute of Social Sciences and Indian Statistical Institute.
North Karnataka, in particular, is exposed to a higher number of days hotter than the threshold, found the study that considered rice, sorghum, finger millet, and pigeon pea.
The study commissioned by Karnataka Agricultural Price Commission to investigate the impact of exposure to high temperature on crop yields, divided Karnataka into three meteorological sub-divisions — north interior, south and coastal.
In the case of rice in kharif season, a per cent increase in EDD above 33 degrees Celsius decrease rice yield by 5 per cent, says Madhura Swaminathan, professor, Economic Analysis Unit, Indian Statistical Institute, and one of the co-authors of the study. When it comes to sorghum, while rainfall and GDD (growing degree days) had a positive impact on crop yield in both rabi and kharif seasons, EDD had a negative impact of 1.89 per cent in rabi and 3.16 per in kharif season.
“Exposure to an extreme temperature that exceeds the critical threshold of the crop has a strong negative effect on yield. This study is perhaps the first of its kind in southern India and for crops other than wheat. It focuses on climate and climate variability, and clearly shows that exposure to extreme heat is the most important effect of climate change on agriculture that can be currently observed in Karnataka,” the paper said.
In case of pigeon pea and finger millet, only EDD was negative and significant. Also, the negative impact of EDD was much stronger than the positive effects of seasonal rainfall. While extreme temperatures resulted in yield decrease of 5.72 per cent in finger millet, the negative impact for pigeon pea was 4.43 per cent.
“Long-term data on annual average temperatures indicates a statistically significant increasing trend, with a range of 0.6 to 0.7 degree Celsius per century for different subdivisions of the state. A rising trend in temperatures in Karnataka points to the possibility of warmer growing seasons and greater likelihood of extreme temperatures in the future. These are matters of serious concern for agricultural productivity in the region,” it said.