Coupling and coordination analysis of urbanization and ecosystem service value in Beijing-Tianjin-Hebei urban agglomeration

Urbanization has an important impact on the regional ecological security pattern, and clarifying the relationship between urbanization and ecosystem services can provide a reference for the regional high-quality sustainable development. Under the background of global economic integration, urban agglomerations have become the main driving force leading economy development in the world. As one of the three major urban agglomerations in China, the Beijing-Tianjin-Hebei urban agglomeration (BTHUA) plays an irreplaceable role in China's social and economic development. This study employed the coupling coordination degree (CCD) model to explore the change characteristics between the two integrated systems and subsystems of urbanization and ecosystem service value (ESV). Results showed that, from 2000 to 2018, the urbanization level of BTHUA has gradually increased, with change trend from the early state dominated by population and land urbanization to the state dominated by population and economic urbanization; the total ecosystem service value (TESV) and per ecosystem service value (PESV) of Chengde were higher than other cities such as Beijing obviously. CCD of urbanization and ESV in BTHUA showed the trend of 'high in the middle and low on both sides in the north-south direction, high in east and low in west in east-west direction', and the CCD at the subsystem scale presented a more coordinated trend. However, there is a gradual degradation of some functions of ecosystem services, and soil conservation and food production functions are urgent concerns in the future.