PolyU research reveals snow droughts continue to threaten global food security and calls for climate-resilient agriculture practices to promote sustainable development
Global climate change is reshaping agricultural ecosystems. As warmer winters become more prevalent, snow droughts caused by insufficient snowfall are becoming more frequent. This leaves winter wheat, which relies on snow cover for insulation and water supply, vulnerable to low-temperature frost damage and water stress, posing a major threat to global food security. A research team from The Hong Kong Polytechnic University (PolyU) has utilised innovative explainable machine learning to uncover the persistent and significant negative impact of snow droughts on winter wheat yields, highlighting that global food security is facing unprecedented challenges. This breakthrough study provides key scientific evidence for building climate-resilient agriculture, ensuring food security and promoting sustainable development.
Led by Prof. Shuo WANG, Associate Professor of the PolyU Department of Land Surveying and Geo-Informatics, a core member of the Research Institute for Land and Space, and a member of the State Key Laboratory of Climate Resilience for Coastal Cities, the study was conducted in collaboration with scholars from the University of Hong Kong and the University of California, Irvine. The findings have been published in the international journal Nature Food.
Over the past 60 years, the frequency of snow droughts across the Northern Hemisphere’s winter wheat croplands has increased significantly. The proportion of croplands affected by snow drought surged from 46–54% in 1960–1970 to 70–99% in 2010–2020, reflecting the fact that snow droughts have evolved from a localised risk into a widespread phenomenon.
The research team developed the XGB-SHAP model framework to accurately identify the direct impact of snow drought on crop yields. The framework combines Extreme Gradient Boosting (XGBoost) with Shapley Additive exPlanations (SHAP) to effectively exclude interference from other climate factors such as high temperature and rainfall, enabling a quantitative analysis of the direct impact of snow drought on winter wheat yields. This study also systematically analysed snow–crop–water interactions, providing a robust empirical basis for developing climate-resilient agricultural systems.
Using the XGB-SHAP framework, the study found that approximately 45% of croplands in the Northern Hemisphere experienced significant adverse impacts from snow droughts, with Europe, Central Asia and the United States being the regions most severely affected. Meanwhile, in East Asia, the yield benefits of longer growing seasons due to warmer winters are gradually diminishing and the regional hydrothermal balance is becoming increasingly unstable. The study also identifies increased fertiliser use, intensified freezing stress and reduced precipitation as the three primary factors contributing to winter wheat’s increased sensitivity to snow drought. While enhanced soil nutrient levels can promote crop growth, they also make crops more dependent on the water supply and thermal insulation provided by snow cover. When snow drought occurs, these factors can amplify the risk of yield loss.
Prof. Shuo Wang noted, “As global warming continues, climate risks are no longer limited to ‘acute stressors’ such as heatwaves, but also include gradually accumulating and far-reaching ‘chronic stressors’ such as snow droughts. As winter wheat is a major commodity in global agricultural trade, the effect of its yield variability can ripple through global trade networks, driving up food prices and potentially leading to regional food security crises.”
Looking ahead, the research team recommends strengthening the climate resilience of agricultural systems by enhancing crop varieties, improving agricultural management and monitoring risks. Alongside intensifying efforts to develop crop varieties with both cold and drought tolerance, agricultural management models have to shift from traditional, input-intensive production to more precise and sustainable nutrient management systems. Furthermore, snow cover monitoring should be incorporated into agricultural risk assessment and early warning systems. Identifying snow drought risks at an early stage and enhancing the resilience of agricultural systems will ensure that stable food production is maintained in the face of climate change, steering global agriculture towards a more sustainable future.
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