Spatiotemporal patterns and driving mechanisms of Urban Green Transition in the Yangtze River Delta Urban Agglomeration, China

Against the backdrop of China's "Dual Carbon" goals, evaluating the urban green transition (UGT) of the Yangtze River Delta Urban Agglomeration (YRDUA) is of vital demonstrative significance for high-quality regional development. To uncover its internal spatiotemporal characteristics and underlying mechanisms, this study systematically evaluates YRDUA panel data from 2012 to 2024 using spatial-econometric models and network analysis tools, including Social Network Analysis (SNA) and the Quadratic Assignment Procedure (QAP). The results indicate that the regional UGT has shifted from scale expansion to quality enhancement, with an "inverted U-shaped" hierarchy distribution, where Tier-3 cities serve as the primary battleground for the transition. Spatially, the region demonstrates strong "club convergence" and has evolved into a highly synergistic, polycentric collaborative ecosystem. Furthermore, the core drivers—green industrial agglomeration and structural upgrading—manifest distinct hierarchical differentiation: relying on environmental governance in Tier-1 cities, capital factors in Tier-2, and external regulations in Tier-3 and Tier-4, while technological conversion and human capital mismatches persist as major bottlenecks. Consequently, these findings provide a robust theoretical foundation for high-density urban agglomerations to implement hierarchical collaborative governance, break spatial lock-ins, and formulate differentiated integration policies.