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Wheat yield to decline as temperatures increase

International group combines models to increase accuracy of prediction

For every degree celsius that the temperature increases, the world stands to lose six per cent of its wheat crop, according to a new global study led by a University of Florida scientist. That’s one-fourth of the annual global wheat trade, which reached 147 million tonnes in 2013.

Senthold Asseng, a UF professor of agricultural and biological engineering, used a computer model approach to reach the finding of temperature increases and wheat production.

“We started this with wheat, as wheat is one of the world’s most important food crops,” said Asseng, whose team’s study was published online Dec. 22 in the journal Nature Climate Change. “The simulations with the multi-crop models showed that warming is already slowing yield gains, despite observed yield increases in the past, at a majority of wheat-growing locations across the globe.”

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For 20 years, scientists have been trying to estimate the effects of temperature increase and climate change on various crops and on wheat production, which accounts for 20 per cent of calories consumed globally.

But different research groups came up with different results.

global temperature and carbon dioxide graph

By pooling models, as part of the global Agricultural Model Intercomparison and Improvement Project (AgMIP), scientists found they can better predict the impact of warmer temperatures on wheat yield, said Asseng, an Institute of Food and Agricultural Sciences faculty member.

Asseng led a group of 50 scientists from 15 countries who devised an ensemble of computer models to increase the accuracy of their predictions. They worked with 30 wheat crop models and tested them against field experiments. In those experiments, average season temperatures ranged from 15 to 32 C, or 59 to 89.6 F.

The ensemble of models consistently simulated crop temperature responses more accurately than did any single model.

In the past 100 years, global temperatures have risen by more than 0.6 and are projected to increase by 2 to 4 C by the end of the century, according to the International Panel on Climate Change.

New heat-tolerant wheat cultivars and crop management are needed to counteract the projected yield decline, and crop models will play a major role in developing new research strategies for that, said Asseng.

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