The Impact and Mechanisms of Yangtze River Delta Regional Integration on the Green and Low-Carbon Development of Cities

Regional integration is a foundation for coordinated regional development and an important pathway for promoting the green and low-carbon development (GLD) (In this paper, GLD refers to green and low-carbon development, while YRD refers to the Yangtze River Delta) of cities. Based on a systematic analysis of the theoretical mechanisms through which regional integration affects the GLD of cities, this study uses changes in the spatial scope of Yangtze River Delta (YRD) regional integration as a quasi-natural experiment and constructs a multi-period DID model to examine its impact. The results show that YRD regional integration significantly improves the GLD efficiency of cities. This conclusion remains valid after a series of robustness tests, including the parallel-trends test, year-by-year PSM-DID, and modern staggered DID estimators. The heterogeneity analysis shows that the promoting effect of regional integration is more significant for megacities, core cities, and especially Shanghai, while its effects on medium-sized cities and cities in Anhui Province have not yet emerged in the short term. The mechanism tests further show that YRD regional integration improves the GLD efficiency of cities mainly by optimizing the energy consumption structure, promoting industrial restructuring, enhancing government attention to GLD, and improving green innovation. The findings provide useful empirical insights for fully leveraging the green and low-carbon effects of YRD regional integration and for promoting GLD in the Yangtze River Economic Belt and even across China.