Rice production in South China is increasingly threatened by more frequent and intense heatwaves, posing substantial risks to national food security. While ratooning rice (RR) has emerged as a promising alternative to middle rice (MR) due to its high resource-use efficiency and economic benefits, the comprehensive and quantitative comparison of climatic risks between these two systems remains elusive. Here, we quantified the spatiotemporal heat stress risks for RR (main season) and MR across South China. RR exhibited significantly lower magnitude and slower increase of heat stress risk during the critical heading stage compared to MR. Specifically, RR experienced an average of 4.6 heatwave days during the critical period, a 23.9% reduction relative to MR (6.0 days). This advantage was consistent across most provinces, with heatwave day reductions ranging from 4.2% to 58.1%. Temporally, the increase in heatwave days for MR (1.0 days/decade) was more than double that of RR (0.46 days/decade). Under future warming (SSP1-2.6/SSP5-8.5), the probability of historical 50-year extreme heat events increases by 20.2–23.5 fold for MR, whereas RR demonstrates superior resilience with a markedly lower increase of 12.6–17.3 fold. We further estimate that scaling up RR cultivation in South China could reduce heat-induced yield losses by approximately 2.0 million tons per year, relative to maintaining MR cultivation. Collectively, our findings demonstrate that the transition from MR to RR represents a pivotal agro-ecological adaptation strategy for mitigating climate risks in rice production under ongoing global warming.

Ratoon rice,Heat stress,climate change adaptation,food security