02.02.2017 |

Climate change may cut some US crop harvests by half, study warns

Higher temperatures, lower soybean yields (Photo: CC0, charlesricardo)

US crop harvests could suffer substantial yield losses due to climate change, new research shows. Without significant reductions in emissions, the production of some of the most important food crops could be reduced by up to 50 per cent by the end of the century, mostly caused by water stress. According to a study published in the journal Nature Communications, maize yields in the US could fall by 49 per cent by 2100. Soybean yields could drop by 40 per cent, while wheat harvests could see a 20 per cent reduction. The research team, which includes scientists from the Potsdam Institute for Climate Impact Research (PIK) and the University of Chicago, developed a computer simulation of how crops responded to rising temperatures and then tested the results against observational data collected from US croplands. They used nine different crop models and showed that these models reproduces the observed average temperature responses of US maize, soybean and wheat yields. “We know from observations that high temperatures can harm crops, but now we have a much better understanding of the processes,” said PIK researcher Bernhard Schauberger, who led the study.

The scientists found that for each day above 30 degrees Celsius (86 Fahrenheit), maize and soybean yields diminished by up to 6% under rainfed conditions. These losses do not even consider extremely high temperatures above 36°C, which are expected to lower yields further, the study says. This would not only have negative impacts for the US, one of the largest crop exporters. Yield losses in the world’s main bread baskets could also lead to higher world market crop prices, which is also negatively affecting food security in poor countries, the authors warn. The researchers identified water stress as the main reason for yield losses. “The losses got substantially reduced when we increased irrigation of fields in the simulation, so water stress resulting from temperature increase seems to be a bigger factor than the heat itself,” said co-author Joshua Elliott from the University of Chicago. They said crops respond to water stress by increased root growth at the expense of above-ground biomass, which means a reduction in yields. According to the scientists, increased irrigation could help to reduce the negative effects of global warming but this is possible only in regions where sufficient water is available. Since this is limited by the lack of water resources in many regions, limiting global warming by cutting emissions is needed to keep crop losses in check. (ab)

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