Beyond mean supply: Indicator-based mapping of ecosystem-service variability and associated factors across the third pole

Most ecosystem-service assessments emphasize mean supply, yet management also depends on how consistently services are delivered. We assessed four regulating services and habitat quality (HQ) across the Qinghai–Tibet Plateau using nine observation years between 2000 and 2023, summarized them in a composite index (CESI), and quantified temporal variability with a relative-variability metric (CVr). An east–west socio-ecological zonation and an Infrastructure-Associated Disturbance Index (IADI) were used to examine regional contrasts. Mean water conservation, soil retention, carbon sequestration and habitat quality decreased from southeast to northwest, whereas wind-erosion prevention was concentrated in the western interior. High CESI variability covered 30.79% of the western Plateau but only 4.41% of the east, and this contrast remained stable in leave-one-year-out and boundary-perturbation tests. Human-pressure relationships were indicator specific: IADI was positively associated with HQ variability, especially in the east, but weakly negatively associated with CESI variability in both subregions. Random-forest and structural-equation analyses consistently showed stronger associations with environmental gradients than with anthropogenic pressure, although anthropogenic predictors provided clearer secondary signals in the east. Together, these results show that mean supply alone can conceal distinct spatial patterns of service inconsistency; pairing supply with variability provides a practical basis for locating less consistent service provision and interpreting its regional environmental and human context.