In what could be seen as an explanation to the decrease in rice productivity in recent years, scientists have shown that air pollution has reduced rice harvest by 20-25 per cent in India in the 1990s.
According to a study carried out by researchers in the University of California, published in the Proceedings of the National Academy of Sciences on Monday, the culprit is atmospheric brown cloud (ABC) — a haze of tiny particles called aerosols which are generated from soot as well as vehicular and industrial emissions.
An India-born scientist, who first identified the ABC over the Indian Ocean and a part of the new study, has expressed concern on the findings of this study.
The haze has been hanging over a large portion of India’s land and sea mass, affecting the climate and crop productivity. Climate change too plays a role in bringing down the productivity by throwing the temperature pattern out of the gear as crops should mature in a particular temperature range only, they say. Scientists find that the combined effects of these was greater after the mid-1980s than before, coinciding with the observed slowdown in harvest growth. They estimate that harvests would have been 20 to 25 per cent higher during some years in the 1990s if the climate hadn’t had a negative impact.
“Greenhouse gases and aerosols in brown clouds are known to be competing factors in global warming. The major finding of this interdisciplinary study is that their effects on rice production are additive, which is clearly an unwelcome surprise,” commented Dr V Ramanathan at the Scripps Institute of Oceanography in California.
Previous research by Dr Ramanathan and his colleagues found that ABC has made the Indian subcontinent drier and cooler.
The latest study indicates that reductions in the two types of pollutants would benefit Indian rice farmers as a reduction in aerosols would enhance rainfall. At the same time reduction in greenhouse gases would reduce the higher night time temperatures that can negatively affect the growth of the rice plant. The findings are in tune with the dip in rice production since the mid-1980s, raising concerns that food shortages could recur. Though several explanations have been proposed, researchers claim that theirs is the first effort to link rice productivity with ABC and climate change.
Japanese study
Interestingly, a couple of months ago, Japanese researchers claimed to have found evidence that fallouts of climate change — increased temperature, rise in the carbon dioxide level and accumulation of excess ozone close to the ground — are reducing rice production in vast swaths of Asia.
The research about the negative impacts of excess carbon dioxide accumulation resulting in crop loss has shattered a long standing myth — a little bit of global warming is good for agriculture. “We had overestimated the beneficial effects of carbon dioxide. We have to be more pessimistic as global warming and climate changes are adversely influencing the food production,” Kazuhiko Kobayashi from Tokyo University told a rice congress last month.
