Study: Combined heat and drought cut wheat yields by 13 per cent on average
A refined crop model shows how hard extreme weather hits the global wheat harvest. Irrigation helps – but its protective effect has weakened over time, the researchers say.
Symbolic image · Photo: Michael Gäbler / Wikimedia Commons, CC BY-SA 3.0 (cropped and resized)
A Chinese research team including Yuchuan Luo (Southwest University), Zhao Zhang (Beijing Normal University) and Fulu Tao (Chinese Academy of Sciences) examined in the journal Nature Food (8 October) how droughts and heatwaves affect wheat yields worldwide. The researchers improved a crop growth model and calculated yields on a ten-kilometre grid. For 1981 to 2015, their model improved skill in reproducing yield losses compared with a multi-model ensemble, they say: by 30 per cent for droughts, 20 per cent for heatwaves and 7 per cent for compound events.
According to the calculations, wheat yields fell by 9.7 per cent on global average during droughts and by 5.8 per cent during heatwaves. When heat and drought strike together, the loss is 13.3 per cent. Irrigation offsets part of these losses, but its protective effect has diminished over time as extremes have intensified, the authors report. Wheat is one of the world's most important staple foods. Context: this is a modelling study. The headline figures come from simulations checked against yield statistics, satellite-derived wheat yield data, weather stations and a disaster database. The abstract gives no uncertainty ranges for the loss figures. The loss figures refer to the period 1981 to 2015.