A meta-analysis of the predicted effects of climate change on wheat yields using simulation studies

Future climate change is expected to affect wheat yields. However, it is uncertain if the overall change in climate will result in wheat yield increases or decreases. This is due to the opposing effects of temperature, precipitation, and CO2 concentration on wheat yields. In this study, a meta-analysis of simulated yield change was conducted to identify the levels of temperature, precipitation and CO2 concentration that result in increasing or decreasing wheat yields. With data from 90 studies using computer modeling, we found that more than 50% of the simulated relative yield change resulted in yield losses when mean temperature change is higher than 2.3 degrees C, or mean precipitation change is null or less, or when CO2 concentration is lower than 395 ppm. A statistical model relating relative yield change to the three considered climatic variables was used to explore a large range of climate change scenarios. Results showed that, in average, the effects of high CO2 concentrations (>640 ppm) outweighed the effects of increasing temperature (up to +2 degrees C) and moderate declines in precipitation (up to 20%), leading to increasing yields. However, these results varied greatly from site to site, likely due to differences in topography, soils and farming practices. These results also do not take into account the effects of pests, diseases and weeds or climate variability, which may act to decrease wheat yields. (C) 2013 Elsevier B.V. All rights reserved.