from The New Scientist:
Rice is arguably the world’s most important food source and helps feed about half the globe’s people. But yields in many areas will drop as the globe warms in future years, a review of studies on rice and climate change suggests.
The poorest parts of the world, including Africa, will probably be hardest hit, the study says. Rice harvests already need to increase by about a third just to keep up with global population growth.
Predicting how a changing climate will affect crop yields is notoriously difficult. Temperature, carbon dioxide concentration and ozone levels all have a big impact on growth. Yet most studies look at just one of these factors, making it difficult to know what the combined effect will be.
It is also hard to know whether results from experiments in greenhouses with artificial climates will hold true in the real world. But when the evidence from some 80 different studies is combined, the outlook is bleak, says Elizabeth Ainsworth of the University of Illinois, Urbana-Champaign.
In regions where the average daily temperatures are expected to rise above 30ºC, rice yields will start to fall off, and the impact will get worse as the temperature increases.
The drop in yield caused by rising temperatures can be counteracted by the boost to photosynthesis provided by the increased levels of carbon dioxide driving climate change. But when Ainsworth pooled the studies, she found that effect is not strong enough to counteract the stress plants suffer at high temperatures.