Over 0.5 billion of the world’s poorest people depend on rice as their staple food. But as temperatures have warmed over the past 25 years, growth rates of rice yields have fallen by 10-20% in Asia, which produces the lion’s share 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.
The study also found that yields increase with higher daytime temperatures, but says that these gains will be lost by faster rising night time temperatures.
The study is the first to assess the impact of both daily maximum and minimum temperatures on irrigated rice production in the field. It looked at data from 277 rice farms in six countries.
“Our study is unique because it uses data collected in farmers’ fields, under real-world conditions,” said Welch. “This is an important addition to what we already know from controlled experiments.”
The researchers say that the mechanism responsible for the yield losses has “not been conclusively identified”. But they suggest that the energy which could be put into yield is lost as a result of increased respiration due to the heat.