Supply and demand of ecosystem services and their interaction with urbanization: The case of Chengdu-Chongqing urban agglomeration

The rapid development of urbanization has profoundly affected the balance between ecosystem supply and demand in urban areas. An in-depth investigation of the relationship between the level of urbanization and the supply and demand of ecosystem services (ES) within urban agglomerations is fundamental to the effective promotion of sustainable regional development. This study, through a comprehensive evaluation of essential ES (water yield, carbon sequestration, food production) and urbanization metrics (population, economy, land use, social factors), investigates the coupling and coordination dynamics within the Chengdu-Chongqing urban agglomeration (CCUA) from 2000 to 2020, employing a zoning framework based on ecological function identification, protection strategies, and prioritization. The results show that the supply of carbon sequestration and food production is decreasing, while the demand for the three ESs is increasing significantly, and the ecological supply-demand balance in the CCUA is weakening, particularly in the Central urban and Chengdu. Despite an overall increase in urbanization, which ostensibly enhances the coordination between urban development and ES supply-demand, a detailed decoupling index analysis reveals a strong decoupling state across the CCUA, suggesting that urban expansion is compromising the balance of ES. This misalignment emphasizes the need for the CCUA to transition towards a green development model promptly. Based on the constructed zoning framework, focusing on each city's ecological service function, supply and demand matching mode, and coupling coordination degree, the CCUA can be divided into a total of 11 types, and the application of the zoning can help to guide the utilization of ecosystem services in the CCUA, the identification of key areas, and the enhancement of the sustainability of urban development.