Evaluation and simulation for ecological risk based on emergy analysis and Pressure-State-Response Model in a coastal city, China

The objective of this study is to evaluate and simulate the ecological risk level of a coastal city, Tianjin's urbanization through an emergy synthesis model. In this study, an ecological risk index system was developed corresponding to the factors of urban ecosystem risk including in Pressure-State-Response model (PSR). Thus, an emergy-based ecological risk evaluation model (EERM) was proposed to evaluate and simulate the risk levels for urban expansion, which offers an integrated evaluation tool in view of urban ecosystem pressure, state and response. Emergy analysis methods are explained, illustrated and used to diagram the urban ecosystem, to evaluate environmental and economic inputs and harvested yield, and to assess the sustainability of the Tianjin during 1995 to 2009. The results have shown that, from 1995 to 2009, the pressure rating of the urban ecology risk in this area had been rising continually. These results comply with relevant laws of correlativity between urbanization and ecological protection in this research area. It is hoped that the evaluation and simulation for ecological risk will provide scientific basis for appraisal of the security and sustainable development of urbanization.