Hotter Nights Threaten Food Security – Rice at Risk

August 8, 2010

Jeff Vincent,, or Tim Lucas, 919/613-8084,

DURHAM, N.C. – Production of rice, the world’s most important crop for ensuring global food security and addressing poverty, will be thwarted as temperatures increase in rice-growing areas with continued climate change, according to a new study by an international team of scientists.

The research team, which included Duke University researcher Jeffrey R. Vincent, 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 yield growth rate by 10 percent to 20 percent in several locations.

Published today in the Proceedings of the National Academy of Sciences, the report 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,” said Jarrod Welch, lead author of the report and graduate student of economics at the University of California, San Diego.

Vincent, who is Clarence F. Korstian Professor of Forest Economics and Management at Duke’s Nicholas School of the Environment, was corresponding author of the study, which 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.

The study used data collected in farmers’ fields, under real-world conditions. This is an important addition to what scientists already know from controlled experiments, Welch and Vincent stressed, because – since 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 three billion people eat rice every day, and more than 60 percent of the world’s one 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 said.

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 found. And if daytime temperatures get too high, they too 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. This will get increasingly worse as temperatures rise further towards the middle of the century,” Welch said.

Welch and Vincent’s coauthors were Maximilian Auffhammer of the University of California, Berkeley; Piedad Moya and Achim Dobermann of the International Rice Research Institute; and David Dawe of the Food and Agriculture Organization of the United Nations.