Crop yields cut by almost half due to India’s dirty air: study

Air pollution in India has become so severe that crop yields are being cut by almost half, scientists have found.

Researchers analysed yields for wheat and rice alongside pollution data, and concluded significant decreases in yield could be attributed to two air pollutants, black carbon and ground level ozone. The finding could also be relevant to farmers in China, as well as having implications for global food security as India is a major rice exporter.

Black carbon is mostly caused by rural cooking stoves, and ozone forms as a result of motor vehicle exhaust, industrial emissions, and chemical solvents reacting in the atmosphere in the presence of sunlight. Both are "short-lived climate pollutants" that exist locally for weeks to months, with ozone damaging the leaves on plants and black carbon reducing the amount of sunlight they receive.

The study looked at both the effects of climate change and the two pollutants on crop yields.

"While temperature has gone up in the last three decades, the levels of smog and pollution have changed much more dramatically," said Jennifer Burney, an environmental scientist at the University of California, San Diego, and co-author of the paper, published in Proceedings of the National Academy of Sciences. "But this was the first time anyone looked at historical data to show these pollutants are having tremendous impacts on crops."

Comparing crop yields in 2010 to what they would be expected to be if temperature, rainfall and pollution remained at 1980 levels, the researchers showed that yields for wheat were on average 36 per cent lower than they otherwise would have been, while rice production decreased by up to 20 per cent. In some higher population states, wheat yields were as much as 50 per cent lower.