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Abstract

Compound water and heat stresses cause great crop yield losses, threatening food security. However, the current extent and future trajectory of these stresses remain uncertain. Here, we developed a compound water-heat stress index (WHSI) to quantify the spatiotemporal variations in co-occurring water and heat stresses around maize flowering in China. We demonstrated that WHSI can effectively capture historical yield variations in major maize-growing regions. Future projections show a substantial increase in compound water-heat stress events, particularly in northeast and northwest of China, driven primarily by rising temperature. By optimizing planting dates and selecting suitable cultivars, compound water-heat stress can be alleviated by more than 70% through dynamic adaptation (site- and year-specific adjustments), representing a potential upper bound of adaptation under the strategies considered. These results highlight the critical role of targeted adaptation measures implemented to mitigate the worsening impact of amplified compound water-heat stress on crop yield.