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Ground-level ozone is damaging plants’ leaves and black carbon is reducing the amount of sunlight they receive. Both pollutants are also damaging human health.
In a new study, researchers have analysed 30 years of data on yields of wheat and rice alongside data on air pollution and climate in India, and concluded that significant decreases in yield could be attributed to two air pollutants, black carbon and ground-level ozone.
Comparing crop yields in 2010 to what they would be expected to be if temperature, rainfall and air pollution remained at their 1980 levels, it was found that crop 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.
Up to 90 per cent of the decrease in potential food production seems to be linked to air pollution, while changes linked to global warming and precipitation levels accounted for the remaining 10 per cent.
Black carbon is made up of tiny soot particles and emanates mainly from combustion in rural cookstoves, but also comes from diesel exhausts. Ozone is a secondary air pollutant from precursor pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) reacting in the atmosphere in the presence of sunlight. The sources of NOx and VOCs are primarily motor vehicle exhaust, industrial chimneys, and chemical solvents.
Ground-level ozone and black carbon are damaging to human health, contributing to premature deaths. Both are known as short-lived climate pollutants that exist in the atmosphere for weeks to months, with ozone damaging plants’ leaves and black carbon reducing the amount of sunlight they receive.
“While temperature’s gone up in the last three decades, the levels of smog and pollution have changed much more dramatically,” says Jennifer Burney, an environmental scientist at the University of California, San Diego, and co-author of the paper, published in the journal Proceedings of the National Academy of Sciences. “But this was the first time anyone looked at historical data to show that these pollutants are having tremendous impacts on crops.”
The results are specific to India’s seasonal patterns, the crops, and its high pollution levels, but may extend to other places with similar problems, such as China.
Measures such as improved cookstove technology for rural areas, cleaner energy production and particle filters on diesel vehicles in urban areas, could go a long way towards reducing the damaging impacts on both agricultural yields and health.
Source: The Guardian and Reuters, 3 and 4 November 2014
The study: Recent climate and air pollution impacts on Indian agriculture. By Jennifer Burney and V. Ramanathan. Link: www.pnas.org/content/early/2014/10/29/1317275111.abstract