A recent study shows that increased levels of pollution in the ozone in Asia are costing China, South Korea, and Japan $63 billion every year in lost rice, maize, and wheat harvests.

The study published on Monday on pollution monitoring data from the region and field experiments shows how ozone affects Asia's harvests more than it was believed before.

The researchers said the results of the study should push policymakers to decrease emissions that produce ozone.

"Air pollution control in North America and Europe succeeded in lowering ozone levels," said Kazuhiko Kobayashi, a co-first author of the study.

"We need to repeat that success across East and South Asia," he told AFP.

Previous evaluations of the ozone effects on staple crops like wheat, rice, and maize have sometimes used varieties that are not predominant in Asia or tested plants grown in pots instead of fields.

More accurately, researchers examined varieties common in the region and experimented with crops both in pots and in fields.

The exposure of rice, wheat, and maize to varying levels of ozone and usage of the resulting crop yields showed how different exposures affected plant development.

They also did a second experiment where the crops were treated with a chemical that protects against the ozone effects to see if the yield increased in line with their estimations.

Food security risks

To know the effects on the real world, the researchers applied ozone data from more than 3,000 monitoring sites in Japan, China, and South Korea to their model.

The result was that 33% of China's wheat crop, 28% of South Korea’s, and 16% of Japan’s are lost every year because of ozone pollution.

As for rice, China lost 23%, South Korea lost nearly 11%, while Japan lost around 5%.

Maize crops in China and South Korea were affected at lower levels. In Japan, the crop is not grown in significant quantities.

The researchers noted that their results were affected by several factors, such as ozone monitors being mostly in urban areas and levels in rural areas being often higher.

They said, surface ozone "poses a threat to food security" due to its effects in a region that provides 90% of the world's rice and 44% of its wheat.

"It has been well known that ozone exerts large impacts on crop production," Kobayashi told AFP.

"Nevertheless, the estimated yield loss in rice, particularly of hybrid type cultivars, may be a bit shocking for those who have learned about it for the first time."