Stage-specific climate risks to winter wheat in China: actionable pathways to reconcile yield loss and protein gains

As the global population continues to rise, ensuring nutrition security has become an increasingly critical concern. Climate change poses significant risks to crop yields and quality, complicating efforts to meet nutritional requirements. Notably, the effects of climate change on wheat grain yield (GY) and grain protein content (GPC) vary across growth stages. This study aims to identify the dominant climate variables and their temporal relevance across key wheat growth stages. By analyzing 15 climate variables across different growth stages, we found that stage-specific assessments substantially improved prediction accuracy, with GY and GPC predictions improving by 33‰ and 77‰, respectively, compared with assessments based on the entire growth period. Projections under Shared Socioeconomic Pathways (SSP) scenarios show national GY declines by 4-18‰ (2030s-2050s), contrasting with GPC increases by 6-15‰, underscoring a yield-quality trade-off. The study also revealed different geographic distributions of climate impacts on GY, GPC and GPY, as well as varying interrelationships between climate change Indicators and the three response variables. We identify key climate change factors at critical growth stages, and find that extreme events at the right crop stage (e.g. frost days during sowing, highest daily maximum temperature at maturity) and local meteorological baseline can positively impact GY and GPC. These findings support a shift from traditional food security to nutrition security, ensuring a stable supply of nutrients for a growing population.