Economies of agglomeration

Archaeology

Kuznets curve

Economic growth

Sustainable development

Biology

Urban agglomeration

China

Economics

Geography

Ecology

Economic geography

Urbanization

Environmental quality

Ecological Indicators

Urbanization is one of the most consequential human activities on earth. The contradictions between urbanization and the eco-environment are particularly prominent in urban agglomerations with high industrial concentrations. Based on the Environmental Kuznets Curve (EKC) theory, we propose the hypothesis of the Urbanization-EKC (UEKC), which states that in the process of urbanization, eco-environmental quality first deteriorates and then improves, following a “U” trend. Taking 19 Chinese urban agglomerations as empirical cases, this paper analyzed the multi-dimensional coupling curves between urbanization and the eco-environment. The results show that the coupling curves between urbanization and the eco-environment are heterogeneous, as a result of differences among urban agglomerations and various eco-environmental indicators. In five mega-urban agglomerations, we found that the coupled curve of urbanization and eco-environmental quality index (EQI) is a compound function containing logarithm and quadratic terms, following the “U” curve shape of “quick down, slow up”; the turning point of EQI improvement was found at an urbanization rate of 47%. The empirical results validate that the UEKC hypothesis is tenable for developed urban agglomerations. This study provides a methodological reference for researching the evolutionary relationship between urbanization and the eco-environment and provides decision support for a more harmonious development of humans and nature in China's urban agglomerations.

The coupling curve between urbanization and the eco-environment: China’s urban agglomeration as a case study