News > Rice yields suffer under global warming
A group of scientists have completed a study that suggests warming global temperatures are having a negative effect on the amount of rice farmers can produce. Yields were found to have fallen by 10-20% over the last 25 years in some areas.The group of mainly USA based scientists studied records from 227 farms in six important rice-producing countries including Thailand, Vietnam, India and China. They studied working, fully-irrigated farms that grow 'green revolution' crops, and span the rice-growing lands of Asia from Tamil Nadu in India to the outskirts of Shanghai.
Describing the findings, which are published in Proceedings of the National Academy of Sciences, lead researcher Jarrod Welch said: "Higher day time temperatures can increase rice yields, but higher night time temperatures have a negative effect. The night time temperatures are rising faster and will cause a net loss in productivity." The mechanism involved is not clear but may involve rice plants having to respire more during warm nights, so expending more energy, without being able to photosynthesise.The 2007 assessment of climate impacts from the Intergovernmental Panel on Climate Change concluded that although a modest temperature rise could increase crop yields in some regions, for "temperature increases more than 3C, average impacts are stressful to all crops assessed and to all regions".