Future heat waves threaten global food supply

Heat waves could significantly reduce crop yields and threaten the global food supply if climate change is not tackled and reversed, a research shows. In a first study of its kind, researchers at Norwich-based University of East Anglia (UEA) have estimated the global effects of extreme temperatures and elevated levels of carbon dioxide (CO2) on the production of maize, wheat and soybean.Earlier studies have found that climate change is projected to reduce maize yields globally by the end of the century under a 'business as usual' scenario for future emissions of greenhouse gases. The study shows that the inclusion of the effects of heat waves, which have not been accounted for in previous modelling calculations, could double the losses of the crop."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," explained Delphine Deryng from the Tyndall Centre for Climate Change Research at University of East Anglia.
At this stage, extreme temperatures can lead to reduced pollen sterility and reduced seed set, greatly reducing the crop yield, she added. The impacts on wheat and soybean are likely to be less profound primarily because of the fertilisation effects that elevated levels of CO2 can have on these crops.The researchers used the global crop model PEGASUS to simulate crop yield responses to 72 climate change scenarios spanning the 21st century. 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 fertilization effects have been overestimated," Deryng noted.In plants, CO2 is central to the process of photosynthesis - the mechanism by which they create food from sunlight, CO2 and water. 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, said the study published in the journal Environmental Research Letters.