Spatiotemporal Evolution, Spatial Network Correlation, and Configurational Pathways of the Synergetic Development of Pollution Reduction, Carbon Reduction, Green Expansion, and Economic Growth in the YREB

As the main battleground for ecological civilisation construction in China, the pollution reduction, carbon reduction, green expansion and economic growth (SD-PCGG) collaborative development quality of the Yangtze River Economic Belt (YREB) is crucial to the overall national strategy. Based on panel data from 2011 to 2024, this study empirically tests using methods such as coupling coordination, spatial kernel density estimation, Gini coefficient, Social Network Analysis (SNA), and Qualitative Comparative Analysis (QCA). The findings are as follows: (1) The SD-PCGG level exhibits a fluctuating upward trend, with the Coupling Coordination Degree (CCD) successfully transitioning from "severe imbalance" to "moderate imbalance." The developmental paradigm has shifted from "downstream-first breakthroughs" toward a "basin-wide inclusive upgrade," thereby transcending traditional economic gradients; however, spatial evolution reveals intensifying internal contradictions, characterised by an increasingly pronounced centre-periphery polarisation. (2) The spatial association network has undergone a structural transformation from a polarised "dense-East, sparse-West" pattern to a polycentric, grid-based collaborative ecosystem. The rise of inland hubs, such as Chongqing and Wuhan, confirms that trends of decentralisation and westward expansion are fostering high-efficiency spatial functional complementarity across the entire basin. (3) Configurational analysis indicates that high-efficiency SD-PCGG is a product of structural synergy within the GMS (Government-Market-Society) framework. The strategic crux lies in pathway substitution and functional compensation: under stable market endowments, capital investment (PCI) and human capital exhibit equivalence relations, enabling cities to substitute rigid administrative mandates with modernised, socialised governance models to mitigate systemic resource scarcities flexibly. (4) Regional analysis identifies a spatial evolutionary logic of driving mechanisms transitioning from "government-led intervention" in the upper reaches to "endogenous synergetic drive" in the lower reaches. In the upper reaches, PCI serves as a critical compensatory lifeline for resource-depleted nodes. In contrast, the middle reaches focus on leveraging institutional dividends to drive transition, and the lower reaches effectively substitute administrative constraints with human capital and social participation.