Published: January 19, 2017
Some of the most important crops risk substantial damage from rising temperatures. To better assess how climate change caused by human greenhouse gas emissions will likely impact wheat, maize and soybean, an international team of scientists now ran an unprecedentedly comprehensive set of computer simulations of US crop yields. The simulations were shown to reproduce the observed strong reduction in past crop yields induced by high temperatures, thereby confirming that they capture one main mechanism for future projections. Importantly, the scientists find that increased irrigation can help to reduce the negative effects of global warming on crops — but this is possible only in regions where sufficient water is available. Eventually limiting global warming is needed to keep crop losses in check.
“We know from observations that high temperatures can harm crops, but now we have a much better understanding of the processes,” says Bernhard Schauberger from the Potsdam Institute for Climate Impact Research, lead author of the study. “The computer simulations that we do are based on robust knowledge from physics, chemistry, biology; on a lot of data and elaborate algorithms. But they of course cannot represent the entire complexity of the crop system, hence we call them models. In our study they have passed a critical test.” The scientists compare the model results to data from actual observations. This way, they can find out if they include the critical factors into their calculations, from temperature to CO2, from irrigation to fertilization.
Without efficient emission reductions, yield losses of 20 percent for wheat are possible by 2100
For every single day above 30°C, maize and soybean plants can lose about 5 percent of their harvest. The simulations have shown that the models capture how rather small heat increases beyond this threshold can result in abrupt and substantial yield losses. Such temperatures will be more frequent under unabated climate change and can severely harm agricultural productivity. Harvest losses from elevated temperatures of 20 percent for wheat, 40 percent for soybean and almost 50 percent for maize, relative to non-elevated temperatures, can be expected at the end of our century without efficient emission reductions. These losses do not even consider extremely high temperatures above 36°C, which are expected to lower yields further.