Thresholds and spatial effects of urbanization on ecosystem service supply-demand relationships: a multiscale study of the Wuhan Metropolitan Area

Rapid urbanization continues to reshape the supply–demand relationships of ecosystem services (ESs), posing increasing risks to regional sustainable development. Previous work has looked at the scale dependence and spatial heterogeneity of urbanization and how they independently impact supply–demand relationships of ESs but they have not been considered jointly. This study investigated the nonlinear effects of urbanization drivers on ES supply–demand relationships in the Wuhan Metropolitan Area (WMA). The supply–demand relationships of grain production (GP), carbon sequestration (CS), and water yield (WY) were analyzed from 2000 to 2020 at 3 km grid, 5 km grid, and town scales using random forest (RF), SHapley Additive exPlanations (SHAP), and multiscale geographically weighted regression (MGWR). The results showed that (1) GP and WY exhibited slight deficits with increasing supply–demand imbalances, whereas CS remained in surplus but with a continuous decline. (2)RF and SHAP showed significant nonlinear responses to built-up land proportion (BUILT), population density (POP), and GDP density (GDP). The importance and response patterns of drivers also exhibited scale dependence. (3) The MGWR indicated that urbanization drivers generally exerted negative effects on the ecosystem service supply–demand ratio (ESDR), while their direction and magnitude exhibited pronounced spatial heterogeneity. Overall, the nonlinear, scale-dependent, and spatially heterogeneous effects of urbanization highlight the importance of incorporating critical thresholds and spatial variation into multiscale ecological management and sustainable urbanization.