Detecting climate change impacts on historical good and bad harvests in global maize and wheat production

Abstract

Stable crop production is the basis for global food security. Climate change has increased extreme climate events, often leading to low yields (bad harvests). However, favorable climatic conditions and elevated carbon dioxide concentrations may also enhance the yields of good years (good harvests) in some locations and seasons. Here, we detect the historical impacts of climate change on good and bad harvests of maize and wheat in 63 and 53 countries, respectively. Good and bad harvests were defined as the three highest and lowest yield years during 2000–2019. Using a random forest-based yield anomaly dataset, we analyzed yield anomalies under historical and non-warming (NW) climate conditions. The NW simulations represent yields without anthropogenic climate change. The impacts of human-induced climate change were quantified as the difference between the two. Negative yield impacts were more widespread than positive impacts. Climate change has worsened bad harvests in 76% of the maize-producing countries and 55% of the wheat-producing countries, both of which are mainly located in the mid-latitudes. In contrast, enhancements in good harvests occurred in 32% and 21% of the countries primarily located at high-latitudes. As a result, the amplitude of interannual yield variability increased in 13% and 6% of maize- and wheat-producing countries, respectively, owing to both enhanced good harvests and worsened bad harvests. During the study period, growing-season mean temperatures in most producing countries remained below the crop-specific optimum levels; therefore, warming improved the thermal conditions for crop growth. Human-induced changes in precipitation play a more important role in bad harvests than temperature, as growing-season precipitation is often below the crop water needs. The findings of this study suggest that the adverse effects of climate change on maize and wheat production outweigh the favorable effects, underscoring the need for climate change mitigation to sustain global food security.