Accelerated urbanization in drylands under regional development strategies intensifies ecological pressures; however, the non-linear coupling thresholds within fragile oasis–desert ecotones remain poorly understood. This study quantifies the spatiotemporal synergy between Ecological Environmental Quality (EEQ) and Urbanization Level (UL) in Kashgar Prefecture, China, from 2005 to 2021. Utilizing the Google Earth Engine (GEE) platform, we developed a tailored Desert Remote Sensing Ecological Index (DRSEI) to filter severe soil background and salinization noise, pairing it with a multidimensional Comprehensive Urbanization Index (CUI). A Coupling Coordination Degree (CCD) model, dual-constraint boundary analysis, Generalized Additive Models (GAM), and GM(1,1) grey forecasting were integrated to analyze non-linear dynamics, identify critical threshold effects, and project future trends. The results reveal that: (1) the DRSEI followed an inverted “N”-shaped trajectory, wherein riparian ecological gains effectively counterbalanced urban-induced marginal degradation; (2) the regional CCD steadily upgraded from “mild imbalance” to “intermediate coordination,” driving a widening “core-periphery” rift between the monocentric growth pole (Kashgar City) and lagging peripheral counties; and (3) dual-constraint boundary analysis and GAM verification confirm significant non-linear interactive effects of EEQ and CUI on the CCD, identifying a stringent “dual-optimum” threshold window required to achieve highest-level coordination. Furthermore, grey forecasting projects a steady, overall upgrading of the regional CCD from 2023 to 2029, with peripheral counties undergoing sequential echelon transitions toward systemic, high-level synergy.
Yuan et al. (2026) studied this question.