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Climate change has affected crop yields

Sun, 8th May 2011

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This week researchers from Stanford University have revealed that, in the last 30 years, corn and wheat crops have dropped by 3.8 and 5.5 per cent in response to climate change. This decrease in production has occurred in spite of technological advances, pest control measures and the use of fertilisers.

wheatPublishing in Science, David Lobell and his team note that all major growing regions for wheat, maize, soybeans and rice have experienced increases in temperature since 1980. The notable exception was the US, which experienced cooling. And, although corn and wheat have seen a drop, soybean and rice crops have remained roughly unaffected across the globe.

To reach their conclusions, the researchers developed two models: one which mimicked the observed increases in climate temperatures; and one which assumed temperatures had stayed the same since 1980. They also used statistical tests to see if precipitation changes affected crop yields. The results demonstrated that increases in temperature had reduced global yields of wheat by 5.5 per cent, and increased rainfall also had a negative effect on crops but it was much less marked than temperature.

Given that the U.S. is a notable exception, it shows that analysing climate change data on a country-by-country scale will be misleading. This team have shown that temperatures in the United States havenít increased in a statistically significant way, and subsequently their crops havenít suffered. But the rest of the world has seen a very obvious and worrying change. And this doesnít mean the U.S. is unaffected, since decreases in food availability across the world will inevitably have an effect on the cost of imports. In fact, the authors argue that it already has.

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