基于系统动力学的城市生态系统建设路径研究——以天津市为例

城市生态系统是一个复杂的巨系统，随着经济社会的发展，城市生态系统面临着诸多环境问题，研究城市生态系统建设路径对城市生态环境的改善具有重要意义.本文将影响城市生态系统建设的宏观因素分为5个主要子系统：经济子系统、人口子系统、环境子系统、资源子系统和能源子系统.利用系统动力学模型（System Dynamics， SD）构建城市生态系统的因果回路图和存量流量图，定量描述人口、资源、环境、能源与经济子系统中各相关变量之间的动态反馈关系，以模拟其建设状况及未来变化趋势.考虑到不同的政策驱动因素对城市生态系统建设的影响不同，设置了自然增长型、人口控制型、环境导向型、科技导向型、资源节约型和平衡发展型6种建设路径，通过改变主要模型参数的值来模拟关键变量的变化.研究发现，城市生态环境问题是人口增速过快、产业发展不均衡、水资源匮乏等综合原因造成的.最适合天津市的发展路径是在控制人口增量的同时加强人才引进政策，以此来提高全市科技发展水平，在增加供水方面不仅要依靠科技进步来促进再生水利用量，还要增加外来调水.

Research on construction path of urban ecosystem based on system dynamics: The case of Tianjin

The urban ecosystem is a complex giant system. With the development of economy and society, the urban ecosystem is facing numerous environmental problems. Therefore, it is of great significance to study the path of urban ecosystem construction for the improvement of urban ecological environment. This paper divides the macro factors which affect the urban ecosystem construction into five main subsystems: economic, population, environmental, resource, and energy subsystem. By means of System Dynamics (SD), we constructed the causal circuit diagram and stock flow diagram of the urban ecosystem to quantitatively describe the dynamic feedback relationship among the relevant variables in the subsystems, so as to simulate the status and future trends of urban ecosystem construction. In the view of the fact that different impacts of different policy drivers on urban ecosystem construction, six construction paths are set, namely, natural growth, population control, environment-oriented, technology-oriented, resource-conserving and balanced development, and the changes of key variables are simulated by changing the parameter values of the model. It is found that the urban ecological environment problem is the result of excessive population growth, uneven industrial development and water shortage. For Tianjin, in order to improve its scientific and technological level, the most suitable development path is to strengthen the talent introduction policy while controlling the population growth. Additionally, in terms of increasing water supply, we should not only rely on increasing consumption of renewable water promoted by scientific and technological progress, but also increasing external water diversion.