Spatiotemporal Changes and Driving Factors of Ecosystem Services in the Yangtze River Delta, China: Insights from XGBoost and Structural Equation Modeling

Ecosystem services (ESs) are the benefits that humans derive from ecosystems. Clarifying their spatiotemporal changes and driving factors is fundamental to regional ecological security. The Yangtze River Delta (YRD) is one of the most urbanized and human-disturbed regions in China. This study quantified six ecosystem service indicators—net primary productivity (NPP), water yield (WY), sediment retention (SR), habitat quality (HQ, a biodiversity-maintenance index), crop production (CP), and carbon storage (TC)—during 2000–2020, and identified their driving factors, non-linear responses, and apparent thresholds by integrating the Theil–Sen/Mann–Kendall test, XGBoost with SHAP, and structural equation modeling (SEM). NPP, SR, and CP increased significantly, TC decreased (p < 0.001), and WY and HQ showed no significant trend. Slope dominated NPP, SR, CP, and TC, whereas precipitation dominated WY and HQ; spatial block cross-validation R2 ranged from 0.68–0.97. Topography (slope, elevation) and climate (precipitation) were the core driving factors, providing a quantitative basis for ecological conservation.