DUKE / UC BERKELEY / UC SAN DIEGO (US)—Global climate change and rising temperatures will harm the production of rice, the world’s most important crop for ensuring global food security and addressing poverty, according to an international team of scientists.

The research team found evidence that the net impact of projected temperature increases will be to slow the growth of rice production in Asia. Rising temperatures during the past 25 years have already cut the growth rate of yields by 10 percent to 20 percent in several locations.

The report, published in the Proceedings of the National Academy of Sciences, analyzed six years of data from 227 irrigated rice farms in six major rice-growing countries in Asia that produce more than 90 percent of the world’s rice.

“We found that as the daily minimum temperature increases, or as nights get hotter, rice yields drop,” says Jarrod Welch, lead author of the report and graduate student of economics at the University of California, San Diego.

The study collected data in farmers’ fields under real-world conditions and is the first to assess the impact of both daily maximum and minimum temperatures on irrigated rice production in farmer-managed rice fields in tropical and subtropical regions of Asia, according to coauthor Jeffrey Vincent, a professor of forest economics and management at Duke University.

This is an important addition to what scientists already know from controlled experiments, Welch and Vincent stress, because farmers can be expected to adapt to changing conditions associated with global warming. Their real-world circumstances and outcomes might differ from those in controlled experimental settings.

Around 3 billion people eat rice every day, and more than 60 percent of the world’s 1 billion poorest and undernourished people who live in Asia depend on rice as their staple food. A decline in rice production will mean more people will slip into poverty and hunger, the researchers note.

Up to a point, higher daytime temperatures can increase rice yield, but future yield losses caused by higher nighttime temperatures will likely outweigh any such gains because temperatures are rising faster at night, the study finds.

And if daytime temperatures get too high, they also start to restrict rice yields, causing an additional loss in production.

“If we cannot change our rice production methods or develop new rice strains that can withstand higher temperatures, there will be a loss in rice production over the next few decades as days and nights get hotter,” Welch says. “This will get increasingly worse as temperatures rise further towards the middle of the century.”

Researchers from the University of California, Berkeley; International Rice Research Institute; and the Food and Agriculture Organization of the United Nations took part in the study.

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