Enhancement of ecological barrier function based on the nonlinear relationship between environmental factors and ecosystem services, Qinghai-Tibetan Plateau

The Qinghai–Tibetan Plateau (QTP) is a critical ecological security barrier for China, playing an indispensable role in ecosystem services (ESs). However, comprehensive assessments of the ecological barrier functions of the QTP under different climate scenarios and their threshold-based optimization remain limited. To address this gap, we integrated multi-source datasets with CMIP6 and applied the InVEST model to simulate ESs across the QTP. Elasticity coefficients were used to identify impact thresholds of driving factors, based on which ecological barrier function zones were delineated and targeted optimization strategies were proposed. The results showed that overall ESs improved from 2000 to 2020. Water yield (WY), food supply (FS), grass production (GP), carbon storage (CS), soil retention (SR), climate regulation (CR), water purification (WP), habitat quality (HQ), and landscape aesthetic value (LA) exhibited increasing trends. Under the SSP1-1.9, SSP2-4.5, and SSP5-8.5 scenarios, ESs increased to varying degrees, with the largest changes occurring under SSP5-8.5. The spatial pattern of ESs remained relatively stable, characterized by higher values in the southeast and lower values in the northwest. Precipitation, temperature, evapotranspiration, and fractional vegetation cover (FVC) initially promoted ESs, but their marginal effects weakened beyond specific thresholds. These thresholds generally increased under higher radiative forcing, indicating enhanced ecosystem sensitivity to climate change. Four ecological zones (ecological restoration key area, ecological risk prevention area, ecological function enhancement area and ecological protection and conservation area) were divided and targeted optimization strategies were proposed. This study provides scientific support for sustainable development and ecological security in the QTP.