Coupling coordination and interaction between urbanization and eco-environment in Cheng-Yu urban agglomeration, China

We built a comprehensive evaluation index system of urbanization in Chengdu-Chongqing (Cheng-Yu) urban agglomeration from four subsystems, including the economic, social, ecological, and urban and rural coordination. The comprehensive evaluation index system of eco-environment was constructed by combining ecological environment carrying capacity and ecological flexibi-lity. The coupling coordination degree model was applied to quantify the coupling coordination degree between urbanization and eco-environment in the prefecture-level cities of Cheng-Yu urban agglo-meration from 2005 to 2018. With GIS spatial analysis, phenomenon analysis and Tapio model, we analyzed the interaction type, evolution path and path of decoupling between urbanization and eco-environment in the prefecture-level cities of Cheng-Yu urban agglomeration. The results showed that the urbanization quality of Cheng-Yu urban agglomeration showed a trend of fluctuation and rise during the study period. Both Chengdu and Chongqing as high value areas showed "double-core" radia-ting to the surrounding areas. The eco-environment quality showed a slowly rising trend. The spatial pattern was a " U " shape with a north opening, high perimeter and low center. The degree of coupling coordination between the urbanization system and the eco-environment system was rising, with a spatial pattern of low in the middle and high in the east and west. The overall level of coupling coordination was relatively high. The type of coupling coordination degree was gradually evolving from near-disorder and reluctant coordination to moderate coordination. The evolution paths of urbanization and eco-environmental interaction were divided into two categories: stable and changing. The stable type included 20 cities in 5 subcategories, with Chengdu, Deyang, Mianyang, etc. being always well-coordination. The change type included 16 cities in 9 subcategories. The coordination degree of Chongqing main urban area, Tongliang and most other cities was improved, showing "rising" development. Hechuan, Zigong and a few other cities showed "sinking" development. The growth rates of both ecological environment and urbanization were positive. The decoupling state of urbanization and ecological environment was mainly characterized by weak decoupling and expansion connection.