Rising emissions are causing severe ozone pollution in some of India’s most populated regions. Pollution in Delhi, the nation’s capital, has reached levels comparable to Beijing, one of the most polluted cities in the world, according to India’s Air Monitoring Center. The number of vehicles on the road in India has nearly tripled in the past decade, with 130 million vehicles on the road in 2013 compared to 50 million in 2003, according to the International Council on Clean Transportation.

Ground-level ozone is formed when nitrogen oxides, carbon monoxide and volatile organic compounds react with sunlight after the chemicals’ release from vehicles, industry, or burning of wood or other plant or animal matter. Ground-level ozone—in addition to its other deleterious effects—can cause leaf damage that stifles plant growth, injuring and killing vegetation. There are currently no air quality standards in India designed to protect agriculture from the effects of ground-level ozone pollution, according to the study.

With accurate crop production data and emission inventories for 2005, the study’s authors chose it as a year representative of the effects of ozone damage over the first decade of the 21^st century.

The bottom-up modeling study simulates ozone on local to regional scales. It quantifies, for the first time, potential impact of ozone on district-wise cotton, soybeans, rice, and wheat crops in India for the first decade of the 21st century.

The researchers calculated the amount of total crop damage from ozone pollution by comparing emissions estimates from 2005 with data about how much ozone each of the four crops could withstand. Plants start to exhibit damage when they are exposed to ozone levels that reach 40 parts per billion or above, according to previous research.

A computer model used by researchers calculated ozone levels during crop growing seasons that were more than 40 to 50 parts per billion over most of the country. The team ran the model with different emissions estimates to come up with an average amount of each crop that was lost due to ozone pollution.

India’s economic loss from ozone’s harm to crops amounted to $1.29 billion in in 2005, the study found. Declines in rice and wheat crops made up the majority of the loss, accounting for a combined $1.16 billion in losses, according to the new research.

The researchers found that wheat—one of the country’s major food sources—is the most impacted crop with losses of 3.5 ± 0.8 million tons (Mt), followed by rice at 2.1 ± 0.8 Mt, with the losses concentrated in central and north India.

On the national scale, this loss is about 9.2% of the cereals required every year (61.2 Mt) under the provision of the recently implemented National Food Security Bill (in 2013) by the Government of India. The nationally aggregated yield loss is sufficient to feed about 94 million people living below poverty line in India, they concluded.

Cotton—one of India’s major commercial crops—lost more than 5% of its 3.3 million metric ton (3.6 million US tons) annual output in 2005, costing the country $70 million, according to the new research.

Ghude said the new paper, which is the first to quantify how much damage India’s ozone pollution has caused the country’s major crops on a national level, could help policymakers craft new ozone pollution standards.

It could also help India, a country with a high rate of poverty, as the country implements a new law that subsidizes grain for two-thirds of the country’s residents, he said.

The new food security bill requires the country to provide 61.2 million metric tons (67.5 million U.S. tons) of cereal grains to India’s poor each year at a subsidized rate. The new study found that the 5.6 million metric tons (6.2 million U.S. tons) of wheat and rice lost to ozone pollution was equal to 9.2 percent of the new law’s subsidized cereal requirement.

Under the new law, residents who qualify to receive cereal at the subsidized rate can purchase 60 kilograms (132 pounds) of grain per year. Based on these numbers, the 5.6 million metric tons (6.2 million US tons) of wheat and rice lost could therefore feed 94 million people in India, according to the new study.

Veerabhadran Ramanathan, a professor of climate and atmospheric sciences at Scripps Institution of Oceanography, at the University of California San Diego and a co-author of the new study, said that unlike most studies, which look at the effect emissions will have on agriculture decades in the future, the new study examined how ozone emissions are already affecting crops in India. He said the new study could help spur interest in the issue and help policymakers enact new air quality standards or mandate use of new technology to cut emissions.

Resources

• Ghude, S. D., C. Jena, D. M. Chate, G. Beig, G. G. Pfister, R. Kumar, and V. Ramanathan (2014), “Reductions in India’s crop yield due to ozone,” Geophys. Res. Lett., 41, 5685–5691, doi: 10.1002/2014GL060930