Modeling regional sustainable development scenarios using the Urbanization and Eco-environment Coupler: Case study of Beijing-Tianjin-Hebei urban agglomeration, China.

China's rapid urbanization has produced problems of excessive resource use and environmental pollution, threatening the country's sustainable development. Previous studies mainly focused on empirical observation of the interactions between urbanization and the eco-environment, mainly using econometric models which lacked detailed explanations of the coupling mechanisms between various elements. No quantitative models have been developed to describe the complex nonlinear relationships between various elements, so our understanding of urbanization and eco-environment coupling is vague, and therefore not conducive to coordinating the relationship between them. Coupling urbanization with the eco-environment allows us to simulate interactions between them and enables us to explore the most suitable scenarios for sustainable development. We designed and developed the Urbanization and Eco-environment Coupler (UEC) using system dynamics to simulate regional urbanization and eco-environment coupling and to compare different sustainable development scenarios. UEC integrates human and natural elements. It includes four urbanization submodels (the economy, society, population and construction land) and five eco-environment submodels (water, arable land, ecology, pollution and energy). UEC can fully represent the nonlinear interactions between these submodels by identifying feedback linkages. This allows us to identify an optimal sustainable regional development pattern. We chose the Beijing-Tianjin-Hebei urban agglomeration as a case study research area and obtained the following results: (1) prioritizing urbanization will accelerate economic growth and increase pollution emissions whereas prioritizing the eco-environment will negatively affect both total population and arable land; (2) when sufficient policy and technical support is directed to a particular area, urbanization may not further degrade the eco-environment; and (3) simulation results for various scenarios show that the key to guaranteeing sustainable development is improving technical and political support rather than further restricting urbanization. The UEC model is a significant aid to improving sustainable regional planning.