Increasing impact of compound agricultural drought and hot events on maize yield in China

Drought episodes with hot events usually trigger dramatic impacts on crop yields. However, most previous studies on climate stress have only focused on individual droughts or hot conditions, leading to a neglect of compound information. Based on various combinations of soil moisture and temperature, we investigated the impact of 6 modes of events, namely, compound drought and cold events, compound wet and hot events, compound agricultural drought and hot events (CADHEs), compound wet and cold events, droughts, and hot events, on maize yield in China. We present evidence from country-level, province-level, and grid-cell yield data that CADHEs have emerged as a major threat to maize yield, with higher yield reduction (as well as a higher probability of yield reduction) than the other 5 soil-moisture- and temperature-related events, including agricultural droughts defined only by soil moisture. The negative maize-yield anomalies due to CADHEs have increased during the past decades at both national and regional scales. The increase in the frequency, spatial extent, and severity of compound events can partly account for this enhanced negative impact on maize yield. The concurrent intensification in the positive soil-moisture-yield relationship and the negative temperature-yield relationship is likely responsible for this change. The negative response of maize yield suggests that if the increase in CADHEs persists, more adaptation and mitigation strategies are needed to ensure sustainable food security.