Ecosystem health and its constraint transitions in Plateau cities: insights from Lhasa, China

Abstract

High-altitude urban ecosystems are exposed to pronounced ecological vulnerability and increasing human pressures. Existing assessments have primarily characterized overall health status and its spatiotemporal variation, whereas temporal changes in the configuration of underlying constraints have received less attention. As the capital of the Xizang Autonomous Region of China, Lhasa’s unique geographic and climatic setting on the Qinghai-Xizang Plateau poses distinctive challenges for ecosystem health assessment. This study examined ecosystem health constraint transitions in Lhasa from 2011 to 2020 using a plateau-adapted “Pressure-State-Response” (PSR) indicator system, obstacle degree analysis, and grey relational analysis. The ecosystem health index fluctuated but exhibited an overall upward trend. Municipal solid waste collection volume (SV) ranked first in obstacle degree in most years, with a mean obstacle contribution of 29.41%, identifying it as a recurrent core constraint within the response subsystem. Energy conservation and environmental protection expenditure intensity (EPI), evapotranspiration (ET), drainage pipeline density (DP), and barren land area (BA) constituted secondary constraints whose relative contributions changed over time. SV had the highest grey relational grade with the ecosystem health index (0.7918), indicating the closest temporal correspondence among indicators. Alternative weights, aggregation methods, and classification thresholds confirmed the robustness of the temporal pattern. By revealing constraint transition patterns in high-altitude urban ecosystem health, this study provides a methodological reference for diagnosing changing constraints and prioritizing management in data-limited plateau cities.