Characteristics of the urban environmental regulation network and its impact on carbon emission efficiency in China

On the basis of 2007–2019 data covering 254 cities in China, we analyze the overall and individual characteristics of the environmental regulation network (ERN) using a modified gravity model and social network analysis (SNA) method and investigate the effect of the degree centrality of the EGN on carbon emission efficiency (CEE). The results suggest that, first, China’s municipal environmental regulations exhibit a significant and complex spatial correlation structure. However, the cities are not connected well to each other, resulting in a loose network structure. Second, cities in the Yangtze River Delta, such as Wuxi, Suzhou, and Shanghai, occupy the center of the network, and the degree centrality of approximately 20% of the cities exceeds the average level. Third, the degree centrality of the ERN increases CEE significantly, but its direction and intensity differ significantly according to geographical location, resource endowment and urban size. Fourth, degree centrality improves CEE by reducing the energy intensity of cities. Green innovation and foreign direct investment can strengthen the positive effect of degree centrality on CEE. Degree centrality enhances the CEE of a region but reduces the CEE of neighboring cities through the spatial spillover effect. Therefore, we should focus on promoting low-carbon and green lifestyles, formulate carbon reduction regulations tailored to local conditions, encourage enterprises to apply green technologies, and strengthen cooperation between cities.