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Posted by wmmbb in Natural Environment.

As the globe gets warmer the prediction of extreme weather events seems to be borne out, but that is just an impression. Then there is the increase over the next century of sea levels. And then the changes in the distribution of rainfall and temperatures that will directly affect the growing of food crops.

A study based on historical data over the last thirty years by Wolfram Schlenker, David Lobell and Justin Costa-Roberts has been published in Science Magazine. They selected four key grain crops and found that rice and soy were holding up overall with both declines and rises in different locations, but that wheat and corn showed a production decline. For some unexplained reason, grain growing in North America were not affected by temperature change.

Richard Harris at National Public Radio reports (via Common Dreams):

The losses caused by warming thus far are still smaller than the gains made though improved agriculture. “We’re not saying yields have gone down, just to make this clear,” Schlenker says. “What we’re saying is yields are lower than they would have been without the climate trend. So yields have still been going up over the last 30 years.”

The study is published online by Science magazine. It shows that these crops have declined about 5 percent over what they would have been in the absence of warming. That sounds small, until you consider that globally, these crops are worth about a trillion dollars a year. Five percent of a trillion dollars is $50 billion, “which I think is quite sizeable,” Schlenker says.

And that number is probably just the beginning. Gerald Nelson at the International Food Policy Research Institute in Washington, D.C., says that as the planet heats up in the coming decades, the 5 percent loss today could easily grow to 20 percent.

“Definitely do not consider shrugging that off,” he says. “We can expect to see higher prices that are going to cause problems around the world.” And most of those problems hit people who can afford it the least.

The study is also reported by The Economist. Predictions are really difficult according to the Science Magazine podcast featuring David Lobell



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