Evaluating Sustainable Development and Coupling Coordination in Western China Under the SDG Framework

Achieving the Sustainable Development Goals (SDGs) requires not only aggregate progress but also more balanced coordination across social, economic, and ecological systems. This issue is especially salient in western China, where development catch-up, ecological fragility, and pronounced intraregional heterogeneity coexist. This study constructs a localized SDG evaluation framework for 12 provincial units of western China from 2000 to 2018, reorganizing the 17 SDGs into social, economic, and ecological subsystems with 106 indicators. The analysis combines entropy-weighted TOPSIS, coupling coordination analysis, regional disparity analysis, spatial autocorrelation analysis, and integrated forecasting. Results show that the composite sustainable development index increased from 0.225 to 0.430, yet subsystem progress was uneven: social sustainability improved fastest, economic sustainability also increased substantially, while ecological sustainability lagged significantly. SDG5, SDG6, SDG10, SDG12, SDG13, and SDG15 emerged as the principal lagging goals. Coupling coordination among the three subsystems improved from near disorder to primary coordination, but economic–ecological and social–ecological links stayed weaker than the social–economic relationship. Provincial disparities were moderate overall but ecological sustainability exhibited greater interprovincial divergence. Spatially, the three subsystems followed distinct trajectories: ecological sustainability shifted from early clustering to a low-level dispersed state, economic sustainability developed an entrenched club-convergence pattern, and social sustainability remained spatially random. Forecasts to 2030 indicate continued social and economic gains alongside persistent ecological lag and subsystem imbalance. These findings indicate that the main sustainability challenge in western China has shifted from general development insufficiency to structural imbalance across goals, subsystems, and provinces, and that regional SDG assessments must move beyond aggregate metrics to identify subsystem coordination, territorial heterogeneity, and spatially differentiated governance pathways.