Global warming to hit rice yield

Global warming affects the productivity of rice crops, threatening future harvests of the grain that currently feeds more than two billion people, the International Rice Research Institute (IRRI) said on Tuesday.
The research institute said in a statement that field studies conducted at its headquarters in the Philippines over the past dozen years along with weather data showed rice yields declined by 15 percent for every one degree Celsius increase in the mean daily temperature.
IRRI attributed this to increased night time temperatures associated with global warming, blamed largely on emissions of gases like carbon dioxide from fossil fuels in cars and factories.
Researchers speculate that increased temperature at night forces the plant to divert more energy to maintain metabolic functions instead of producing greater biomass and grain yield, IRRI said.
Temperatures are projected to rise globally by 1.5 to 4.5 degrees Celsius in the coming century, three to nine times more than in the past century, it said.
"Rice yields were found to decrease by 10 percent for each one degree Celsius increase in minimum night time temperature," IRRI said.
"But because the increase in night time temperatures was threefold greater than the increase in daytime temperature, rice yields declined by 15 percent for every one degree Celsius increase in mean daily temperature."
IRRI said the new estimate is two times greater than previous projection of global warming effects on rice yields that emerged from theoretical models.
"Harvest shortfalls induced by global warming would likely be much more widespread and persistent. Left unchecked, they could undermine food security and political stability," IRRI said.
"These findings are important for predicting the effects of global warming on food security because rice is the staple food for two billion people, or about one-half of the human population."
IRRI said the study was made by a nine-man research team headed by its crop physiologist Shaobing Peng.
The researchers said the next challenge was to develop new rice varieties that can still yield well despite any increase in temperatures in rice growing areas, IRRI said.