Spatiotemporal pattern and system coupling coordination evaluation of green low-carbon circular development: A case study of nine cities in Guizhou province, China

Green low-carbon circular development (GLCD) provides an integrated perspective for reconciling environmental protection, carbon mitigation, resource efficiency, and economic development, yet its spatiotemporal heterogeneity and internal coordination remain insufficiently understood at the intra-provincial scale. This study develops an Integrated Spatiotemporal CRITIC-G1-Grey Relational TOPSIS (IS-CG-GRTOPSIS) framework, incorporating region-specific indicators to reflect the ecological and resource characteristics of Guizhou's karst environment, to evaluate GLCD across nine prefecture-level administrative units in Guizhou Province from 2013 to 2022. Kernel density estimation is further employed to examine the evolution of the spatial distribution, while an Improved Coupling Coordination Degree Model (ICCDM) is used to characterize interactions and coordination among the green, low-carbon, circular, and economic development subsystems. The results show that GLCD exhibited an overall fluctuating upward trajectory, reaching a peak of 0.7763 in 2019 before declining and subsequently recovering. Among the four subsystems, low-carbon development achieved the highest level, followed by green, economic, and circular development, with circular development remaining the most persistent weakness. Substantial spatial disparities were observed: Guiyang consistently exhibited the highest GLCD level, whereas Bijie remained at the lowest level, with a center–periphery gradient associated with the concentration of economic, technological, and policy resources. Although the four subsystems displayed relatively high coupling intensity, their coordination remained comparatively limited, with a mean coordination degree of 0.6055. Weak economic and circular development, together with insufficient low-carbon–circular coordination, constrained systemic coordination. These findings highlight the need to strengthen circular resource use, reduce intra-provincial disparities, and enhance cross-subsystem coordination in regional green transformation.