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Climate: Rise in heatwaves threatens food crops

Wheat field in Upper Austria

A wheat field in Upper Austria ripens under a summer sun.

North American corn belt could be hit especially hard

By Summit Voice

FRISCO — While some plants will grow better with more carbon dioxide in the atmosphere, the overall warming caused by greenhouse gases poses a serious threat to food crops — especially the expected increase in heatwaves.

Scientists at the University of East Anglia took a close look at wheat, maize and soybeans to try and estimate impacts to global food production. The findings were published this week in Environmental Research Letters.

Previous studies had already shown that climate change will reduce maze yields by mid-century, but the new study added potential heatwaves to the mix, showing that there is significant chance for catastrophic crop failures as heatwaves become more frequent and intense.

“Instances of extreme temperatures, brought about by a large increase in global mean temperature, can be detrimental to crops at any stage of their development, but in particular around anthesis—the flowering period of the plant,” said climate researcher Delphine Deryng, from the Tyndall Centre for Climate Change Research at the University of East Anglia. “At this stage, extreme temperatures can lead to reduced pollen sterility and reduced seed set, greatly reducing the crop yield.”

The impacts on wheat and soybean are likely to be less profound, primarily because of the fertilization effects that elevated levels of CO2 can have on these crops. When there is more CO2 in the atmosphere, the leaves of plants can capture more of it, resulting in an overall increase in the biomass of the plant.

In addition, plants are able to manage their water use much more efficiently in when more CO2 is available, resulting in better tolerance to drought episodes. However, it is not clear whether these CO2 fertilization effects will actually occur in the field owing to interactions with other factors.

If the CO2 fertilization effects do occur, the researchers found that the yields of wheat and soybean are expected to increase throughout the 21st century under a “business-as-usual” scenario; however, the increases are projected to be significantly offset by the effects of heat waves, as these plants are still vulnerable to the effects of extreme temperatures.

The study also identified particular areas where heat waves are expected to have the largest negative effects on crop yields. Some of the largest affected areas are key for crop production, for example the North American corn belt for maize. When the CO2 fertilization effects are not taken into account, the researchers found a net decrease in yields in all three crops, intensified by extreme heat stress, for the top-five producing countries of each crop.

“Our results show that maize yields are expected to be negatively affected by climate change, while the impacts on wheat and soybean are generally positive, unless CO2 fertilisation effects have been overestimated,” Deryng said.

“However, extreme heat stress reinforced by ‘business-as-usual’ reduces the beneficial effects considerably in these two crops. Climate mitigation policy would help reduce risks of serious negative impacts on maize worldwide and reduce risks of extreme heat stress that threaten global crop production.”

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