Sustainable Urbanization: Unpacking the Link Between Urban Clusters and Environmental Protection

Urban clusters are the main trend of current and future urbanization worldwide, but their impact on environmental pollution has been controversial. This paper explores this issue in the context of urban development in China, and analyzes the underlying mechanisms, using panel data from 285 Chinese cities spanning 2006 to 2021. The findings show that a one unit increase in the degree of urban cluster is associated with a reduction in the comprehensive pollution index by approximately 7.5%, and the main mechanisms by which urban clusters facilitate environmental protection are congestion alleviation, industry structural optimization, and technological innovation. Firstly, urban clusters reduce environmental pollution by mitigating the crowding effects associated with urban expansion, although this alleviation is predominantly observed in larger cities. Secondly, urban clusters foster the upgrading of urban industrial structures, thereby decreasing environmental pollution. However, in less developed cities where industrialization is a major development goal, the impact of structural optimization is less pronounced. Finally, technological innovations, including advances in technologies of energy conservation and emission reduction, have assisted in the transformation of the economic growth model, which has reduced environmental pollution. Looking ahead, the urban cluster remains a pivotal strategic direction for social development, and planning and construction of urban clusters should actively incorporate environmental benefit considerations.