City-level environmental performance and the spatial structure of China's three coastal city clusters

Cities' environmental efficiency (measured in terms of green total factor productivity, GTFP) have been found in the existing literature to correlate spatially. However, the spatial structure of the interrelations between cities' GTFP have not yet been determined. In this study, we attempted to characterize city-level spatial networks of GTFP by investigating China's major three coastal city clusters: Jing-Jin-Ji (JJJ), Yangtze River Delta (YRD), and Pearl River Delta (PRD). We estimated the GTFP of 38 cities within these three coastal city clusters by applying a super-efficiency slack-based measure (SBM) within a data envelopment analysis (DEA) approach, constructed a spatial network of GTFP for each city cluster based on gravity model, traced out the centralities and subgroups of each GTFP network by conducting social network analysis, and then investigated the socioeconomic factors correlating to GTFP interrelation between cities. The results are as follows: First, the average GTFP in the three clusters increased from 2010 to 2021, as did the industrial value added in these regions. In addition, average GTFP increased the most in PRD region relative to the other two clusters. Second, centers of the spatial network of GTFP exist in these three regions. These are as follows: Beijing, Tianjin, and Langfang in JJJ region; Wuxi, Suzhou, and Yangzhou in YRD region; and Guangzhou and Foshan in PRD region. In the JJJ and YRD regions, the composition of the subgroups containing cities with greater closeness of GTFP underwent significant changes between 2010 and 2021, whereas the composition of the subgroup in the PRD region did not change as much. Third, differences in terms of industrial structure and distance between two cities are key underlying factors that influence the interrelation of GTFP between these cities. The characteristics of the spatial networks of GTFP in the three city clusters imply that improving the balance between the central cities and other noncentral cities to alleviate the misallocations between cities and economic resources could result in an increase in the overall efficiency of economic growth and environmental improvement.