Coupling coordination relationship between human activities and water-related ecosystem services supply–demand in the Qinghai–Tibet Plateau

Amid intensified human activities and growing imbalances between ecosystem service supply and demand, clarifying the coordination mechanisms between human and ecological systems has become a key issue for regional sustainable development. Based on the coupling coordination degree (CCD) model, this study systematically evaluates the spatiotemporal dynamics, driving mechanisms, and nonlinear response patterns of the relationship between human activity intensity and the supply–demand ratio of water-related ecosystem services on the Qinghai–Tibet Plateau from 2000 to 2020 at the watershed scale. The results reveal that the overall CCD across the plateau is relatively low, with nearly half of the region in an uncoordinated state, particularly in northwestern inland basins. Over the past two decades, the CCD has declined by 2.8 %, with degradation observed across 61.2 % of the total area. Even in basins with relatively high coordination levels, local declines were detected, indicating widespread and latent ecological risks. A typical inverted “U”-shaped nonlinear relationship was found between CCD and HAI, implying an optimal coordination threshold: moderate human activities may promote coordination, while excessive disturbance leads to imbalance. Vegetation and climatic factors dominate the driving mechanism, with NDVI and precipitation showing the most significant impacts. The study recommends adopting watershed-based differentiated regulation, with priority given to northwestern regions where CCD declines rapidly, alongside systematic ecological management strategies to sustain long-term ecosystem–human coordination.