Regional heatwave variations in China pose a threat to summer grain yields

Abstract

Global warming has led to an increase in both heatwave frequency and temperature, posing a significant threat to agricultural productivity and food security worldwide. This study aims to investigate the relationship between heatwave patterns and grain yields in China, a critical region for global food security. We utilized the Mann-Kendall (MK) test, bivariate correlation analysis, and network structure similarity (NSS) analysis to examine data spanning from 1961 to 2020 across Chinese provinces. The study results show that over the past six decades, 93.5% of China’s 31 provinces have seen a significant increase in heatwave frequency, which has primarily negatively correlated with grain yields, particularly with summer grain yields. In 22 major summer grain-growing provinces, over 70% of cases show a significant correlation between heatwaves and summer grain yields. Specifically, 9 provinces exhibit linear correlations, while 7 show nonlinear correlations. This correlation has further intensified over the past 40 years. Yunnan and Guangxi have the highest heatwave-related summer grain yields, averaging 1200 kg/ha annually (21.9% of the national average in 2020). Guizhou and Ningxia average 1000 kg/ha, while other provinces average less than 310 kg/ha. Heatwaves across most regions of China demonstrate an increasing trend, exhibiting predominantly negative correlations with grain yields - particularly summer grain. This study pioneers a novel quantification framework for assessing heatwave-induced yield impacts, providing a robust basis for analyzing the climate-food security nexus and developing targeted mitigation strategies.