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Friday, March 21, 2014

Heatwaves could threaten food crops, study warns

Extreme temperatures could hit key crops such as maize, wheat and soybean if climate change not addressed

from Press Association,, March 20, 2014

Corn in a field in Godewaersvelde, France. Extreme heat could hit key crops in the future, a new study says
Corn in a field in Godewaersvelde, France. Extreme heat could hit key crops in the future, a new study says Photograph: PHILIPPE HUGUEN/AFP/Getty Images
Future heatwaves could threaten key global food crops if climate change is not addressed, according to a British study.
Researchers came to the conclusion after estimating the effects of extreme temperatures and raised carbon dioxide levels on maize, wheat and soybean production. 

While more C02 in the atmosphere may boost plant growth, this effect is likely to be counteracted by extreme heat, they warn.
Crops are especially vulnerable to heat around anthesis, the flowering period of the plant.
“At this stage, extreme temperatures can lead to reduced pollen sterility and reduced seed set, greatly reducing the crop yield,” said lead scientist Delphine Deryng, from the Tyndall Centre for Climate Change Research at the University of East Anglia.
Earlier studies found that climate change is likely to reduce maize yields by the end of the century under a “business-as-usual” greenhouse gas emissions scenario. 
But factoring in the effects of heat waves could double losses of the crop, claim the authors of the new study published in the Institute of Physics journal Environmental Research Letters.
Impacts on wheat and soybean were expected to be less profound because of the fertilisation effects of raised CO2. 
Yields of both crops are likely to increase throughout the 21st century with “business-as-usual” emissions. But they would be significantly eroded by heatwaves, say the researchers.
A quarter of the positive impact on soybean production would be lost - while the benefit to wheat would be cut by 52%, the scientists estimate.
Some of the largest areas likely to be affected by heatwaves are also important crop production, one example being the North American corn belt.
Before taking CO2 into account, the scientists found a net yield decrease in all three crops – intensified by extreme heat stress – in the top five producing countries for 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,” said Ms Deryng.
“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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