Two Decades of Ecological Quality Evolution Along the Sichuan‐Tibet Highway: Improvement, Localized Degradation and Grazing Intensity Dominating Changes Post‐2010

Abstract

The environmental quality and soil erosion dynamics of the eastern margin of the Tibetan Plateau are vital to regional sustainability, since it is an ecologically sensitive area. In this study, we combined the Remote Sensing Ecological Index (RSEI) and Modified Universal Soil Loss Equation (RUSLE) model to develop a Composite Ecological Quality Index (CEQI). This approach was used to examine the spatio‐temporal distribution patterns and driving factors of ecological quality and soil erosion in the transition zone from the Tibetan Plateau–Hengduan Mountains to Chengdu Plain, over the past 20 years (2000–2020). The CEQI results showed a 24% improvement in the study area's ecological quality, and a major east–west gradient difference was observed, with the eastern plains experiencing significant improvements as a result of China's Grain‐for‐Green Project. Moreover, the central and western high‐altitude areas experienced environmental degradation due to the impact of human activities, such as grazing intensity and changes in natural factors that caused the RSEI to decrease by 10%. This study also found a 2.61% increase in soil erosion modulus, with severe erosion concentrated in the Qamdo–Nagqu area where the interaction between climate change and topography was a key driver in the spatial differentiation. The optimal parameters‐based geographical detector (OPGD) and random forest model (RFM) further showed that precipitation, temperature, and land use dominated changes in environmental quality before 2010. The combined effects of grazing intensity, temperature, and precipitation explained the changes in ecological quality after 2010 with the government's implementation of environmental policies.