Dire need for quantification of environmental impacts associated with breeding climate-resilient crops

As China's breadbasket, the Yangtze River Basin plays a critical role in global food security, yet its agricultural stability is increasingly threatened by the climate emergency. This study aimed to (1) identify the critical climatic variables that drive wheat yield variability across Yangtze River Basin; (2) reveal the key climatic variables that contribute to regional yield gaps, and (3) quantify yield increase and associated environmental costs under current nitrogen application rates and estimate the nitrogen fertiliser required to achieve full yield potential with improved genetic traits. We combined process-based crop model knowledge, fine-scale municipal wheat yield data (1980–2020) and statistical analytics to benchmark regional yield gaps under historical and future climates and we then analysed 8192 hypothetical genotypes with diverse yet realistic ranges of phenology, growth, radiation use efficiency and yield components to assess their impact on reducing yield gaps and associated environmental costs. We found that many arable areas exhibited statistically significant correlations (R 2 = 0.94) between climate and wheat yield variability. Changes in precipitation explained the largest proportion of yield variance (R 2 = 0.38), while temperature (R 2 = 0.31) and solar radiation (R 2 = 0.29) exerted nearly identical influences on wheat yield fluctuations. Yield gaps were well explained by photothermal quotients, which ranged from 0.55 to 1.14 across the Yangtze River Basin. Due to increased extreme climatic events, simulated rainfed wheat yields decreased by 12 % and 24 % in 2050s under emissions scenarios SSP245 and SSP585, respectively. Adoption of cultivars with optimised traits (higher RUE and larger grain size) could increase grain yield by 61–80 % under current and future climate. However, trait-optimisation for yield revealed clear trade-offs for nitrogen demand (16–36 % increase), N 2 O emissions (30–50 % increase), greenhouse gas emission intensity (24–35 % increase) and nitrogen-use efficiency (13–21 % decrease), heralding dire ramifications for breeding programs that optimize traits for productivity benefits alone. We advocate that crop breeding programs include sustainability indicators encompassing nitrogen demand, use, and use-efficiency to avoid environmental impacts associated with increasing yields to feed a burgeoning global population. • Changes in rainfall explained the largest proportion of wheat yield variance • Regional yield gaps linked to differences in photothermal quotient • Wheat yields may decline due to more extreme events under future climates • Climate-resilient wheat breeding can offset negative climate change effects • Significant tradeoffs exist between ideotypes and environmental sustainability