The impact and transmission mechanism of environmental regulation on green total factor productivity in the Yangtze River Economic Belt

Against the strategic backdrop of prioritizing ecological conservation and pursuing green development in the Yangtze River Economic Belt (YREB), balancing economic growth with environmental protection is critical for sustainable development. This study focuses on the impact of environmental regulation (ER) on green total factor productivity (GTFP) and its underlying mechanisms, using panel data from 110 YREB cities spanning 2006–2023. We adopt the EBM-GML model to accurately estimate GTFP, construct a comprehensive ER index via the entropy-weighted TOPSIS method (integrating command-and-control, market-incentive, and public-participation tools), and employ two-way fixed effects, mediation effects, and threshold effects models for empirical analysis. Results reveal a U-shaped relationship between ER and GTFP, which is more pronounced in cities along the Yangtze River mainstem, non-resource-based cities, and large-sized cities, with a threshold value of 0.264. Technological innovation, industrial structure optimization, and foreign direct investment (FDI) serve as significant mediation channels. Further analysis confirms that the synergistic effect of ER and GTFP promotes long-term regional economic growth. Three key innovations of this study are as follows: (1) developing a multidimensional ER index to reflect tool heterogeneity; (2) establishing a multi-mechanism analytical framework integrating technological innovation, industrial structure, and FDI; (3) exploring the long-term economic effects of ER-GTFP synergy. This study provides theoretical support for local governments to establish threshold warning mechanisms and three-dimensional coordination mechanisms, thereby balancing short-term and long-term economic-environmental goals.