Controlling air pollution could help curb projected declines in global food supplies, a new study says, suggesting policymakers should consider both climate change and ozone pollution in efforts to ensure the world has enough food.
Scientists have largely neglected the interactions between rising temperatures and ozone pollution, which is known to damage crops. But the complex linkages can be significant, said the study, published in the latest issue of the journal Nature Climate Change.
It explored the global production of four food staples - rice, wheat, corn and soy - finding that effects will vary between regions, and some crops are more strongly affected by one of the two factors. Wheat is very sensitive to ozone exposure, while corn is more adversely impacted by heat, for example.
Warmer temperatures can increase ozone production, said researchers at Massachusetts Institute of Technology (MIT), who carried out the study. Ozone is a gas - a form of oxygen - that is explosive and toxic.
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The increased use of clean energy sources that do not emit either greenhouse gases or conventional air pollutants, such as wind and solar energy, would be doubly beneficial to global food security, as they do not contribute to either climate change or increased surface-ozone concentrations
Denise L. Mauzerall, professor of environmental engineering, Princeton University
Given that farm production is very sensitive to ozone pollution, the study shows “how important it is to think about the agricultural implications of air-quality regulations. Ozone is something that we understand the causes of, and the steps that need to be taken to improve air quality,” said Colette Heald, one of the authors and an MIT associate professor of civil and environmental engineering.
In the United States, for example, tougher air quality regulations will likely lead to a sharp drop in ozone pollution, mitigating its impact on crops. In other regions, the outcome will be shaped by domestic air pollution policies, Heald said. “An air-quality cleanup would improve crop yields,” she added.
The researchers found air pollution will play a part in shaping undernourishment in developing countries. Under a pessimistic air quality scenario, the malnutrition rate may increase from 18 to 27 per cent by 2050. Under a more optimistic scenario, it would still go up but the increase would be cut almost in half.
Global warming alone may reduce crop yields globally by about 10 per cent by 2050, the study said. But under some scenarios, pollution control measures could offset a proportion of the expected declines.
The damage caused by ozone pollution can be hard to identify, because it resembles other plant illnesses, producing flecks on leaves and discoloration, MIT said.
The researchers found, for example, that 46 per cent of damage to soybean crops that had previously been attributed to heat was actually caused by increased ozone.
The projections exclude the complex effect of rising levels of carbon dioxide, a major greenhouse gas that could also help stem falls in global food supplies, they noted.
Denise L. Mauzerall, a professor of environmental engineering at Princeton University who was not involved in the study, described the finding that air pollution controls could improve agricultural yields and partially offset the negative effects of climate change on yields as “important”.
“The increased use of clean energy sources that do not emit either greenhouse gases or conventional air pollutants, such as wind and solar energy, would be doubly beneficial to global food security, as they do not contribute to either climate change or increased surface-ozone concentrations,” Mauzerall said in a statement.
