Changes in climate-crop yield relationships affect risks of crop yield reduction

The relationship between climate variables (e.g., precipitation and temperature) and crop yield has been used to assess the impacts of climate extremes (e.g., droughts, heatwaves) on crop yield, which is commonly assumed to be time-invariant. However, climate-yield relationships may change over time due to the influence of global warming and human interventions. In particular, the concurrent changes in the precipitation-yield relationship and the temperature-yield relationship could pose challenges to the development of adaptation measures for agriculture planning and management. The objective of this study is to propose a statistical approach to estimate the risk of crop yield reduction under the dry condition, hot condition, and compound dry-hot condition due to concurrent changes in climate-yield relationships. Results show that the relationship between climate and maize yield in the top ten maize-producing countries has changed from 1961-1988 to 1989-2016. The risk of crop yield reduction generally increases with enhanced dependence between dry conditions and crop yield (or hot conditions and crop yield). Based on the multivariate distribution, results show that the risk of maize yield reduction increases for the majority of these countries under compound dry-hot conditions due to concurrent changes in climate-yield relationships. Results of this study are expected to provide useful insights for assessing agriculture vulnerability under global warming.