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Warming Threatens to Cut Crop Yields

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Posted on Aug 2, 2014

    Food for thought: a heap of newly-harvested maize in Vietnam. Photo by Bui Thuy Dao Nguyen via Wikimedia Commons

By Kieran Cooke, Climate News Network

This piece first appeared at Climate News Network.

LONDON—Projecting the impact of climate change on global food production is no easy task. A warming climate might result in better crop yields in one region, but cause drought and crop failure in another.

A new US study, published in the journal Environmental Letters, assesses the odds of a major slowdown in global food production over the next 20 years.

Overall, the study’s authors say, the likelihood of a sharp drop in yields of crops vital to food supply, such as wheat and maize, is “not very high”—but global warming does markedly increase the chance of such events happening. The risk to global food supplies is about 20 times greater when man-made climate change is taken into account.

“Climate change has substantially increased the prospect that crop production will fail to keep up with rising demand in the next 20 years,” says Claudia Tebaldi, a research scientist at the National Center for Atmospheric Research and a co-author of the study.

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Climate trends

Tebaldi, together with David Lobell, an associate director of the Center on Food Security and the Environment at California’s Stanford University, used computer models of global climate trends, together with data on weather patterns and crops, to calculate the odds of a major downturn in food supplies.

“I’m often asked whether climate change will threaten food supply, as if it’s a simple yes or no answer,” Lobell says.

“The truth is that, over a period of 10 or 20 years, it depends largely on how fast the Earth warms, and we can’t predict the pace of warming very precisely. So the best we can do is try to determine the odds.”

Yields of crops such as maize and wheat have typically increased by between one and two per cent a year over recent decades. This trend, says the study, needs to be maintained to cope with population growth, greater per capita food consumption, and the increased use of crops for biofuels.

The authors of the study—which was funded by the US government’s National Science Foundation and the US Department of Energy—found that under what they term natural climate shifts, the odds on that trend slowing up to 2030 were only 1 in 200.

Global food supplies

However, when human-induced global warming is taken into account, the odds shorten to one in 10 for a slowing in yields of maize and one in 20 for wheat production. Such cutbacks, says the study, would have a major impact on global food supplies at a time when demand is growing sharply.

Tebaldi and Lobell say an increase of 1?C in temperature is capable of slowing maize yields by 7% and wheat yields by 6%, although there are regional variations to these figures.

The study says a slowdown in yields of maize and wheat could, in theory, be offset by shifting planting to cooler regions, but there is little sign that such shifts are happening—at least not quickly enough to take account of warmer temperatures.

“We can’t predict whether a major slowdown in crop growth will actually happen, and the odds are still fairly low,” says Tebaldi.

“But climate change has increased the odds to the point that organisations concerned with food security or global stability need to be aware of this risk.”


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