Spatial heterogeneity and environmental drivers of drought vulnerability in the Yangtze River Basin

Drought-induced ecological vulnerability is intensifying under global climate change, threatening ecosystem stability and function. Using the Yangtze River Basin (YRB) as a case study, we constructed a Drought Vulnerability Index integrating exposure, sensitivity, and resilience—three core dimensions defined in the IPCC framework. Exposure was represented by drought severity and duration, while sensitivity and resilience were derived from autoregressive modeling of vegetation dynamics using vegetation and climate data from 2001 to 2023. We employed XGBoost with SHAP analysis to disentangle the drivers of spatial heterogeneity. Results reveal strong spatial contrasts: the central-northern YRB shows the highest vulnerability due to concurrent high exposure and sensitivity with low resilience, whereas the western highlands exhibit comparatively low vulnerability despite high exposure, supported by stronger resilience. Quantitative analysis confirms resilience as the dominant determinant of vulnerability, with over 65 % of vegetated pixels showing a significant negative correlation (R < –0.8, p < 0.05) between resilience and vulnerability. Among environmental drivers, altitude, precipitation, and species richness exerted the greatest influence, often with non-linear or threshold effects. Notably, altitude displayed a U-shaped relationship, with both lowlands and highlands being more vulnerable. These findings highlight the central role of resilience in modulating drought vulnerability and provide a robust indicator-based framework for assessing ecological risk and guiding resilience-oriented adaptation strategies under climate extremes.