Accessing on the sustainability of urban ecological-economic systems by means of a coupled emergy and system dynamics model: A case study of Beijing

Due to high population densities and rapid economic development, great number of cities worldwide rely heavily on external resources, and many are experiencing serious environmental pollution. Municipal governments are facing the issue of balancing the relationship between economic growth and environmental preservation. An urban system is an open, complex, dynamic ecological-economic system with different types of materials and resources. This paper combines emergy theory and System Dynamics (SD) and establishes an emergy-flow SD model of an urban eco-economic system that includes economic, population, waste and emergy sub-models. Three scenarios with different economic growth rates and investments in environmental preservation are designed to analyze the sustainable development capacity of Beijing under different scenarios. The results of the analysis show that current economic development in Beijing highly depends on resources consumption, especially the consumption of imported resources. Based on the current growth rate, development in Beijing will heavily depend on external resources that may make the system being more fragile in the future. A lower economic growth rate and a small increase in environmental preservation investment are more suitable for in Beijing than area higher economic growth rate and a large increase in environmental preservation investment.