Ecological Risk Analysis Models Based on the Emergy Value of Ecosystem Services: A Case Study of Gansu Province in China

Ecological risk analysis is a new marginal subject that studies issues on risk theory, modern ecology and environmental science, etc. Currently, quantitative assessing and integrative study of ecological risk is a significant issue in the world. At the macrocosm scale we have a practice study on risk analysis based on the value of ecosystem services by integrating the quantification of the value of ecosystem services with the model of risk analysis. We establish an ecological risk analysis models: the model of ecological value at risk (EVR) and the information diffusion model. They provide a quantitative method for the ecological risk analysis. Based on the models and the method for evaluating the value of ecosystem services: emergy value of ecosystem services, We select Gansu province in western China, as an example for application of our study. According to the historical data (1980-2001), we calculate the emergy value of ecosystem services in Gansu province and use the EVR model to estimate value of ecosystem services at risk under certain confidence level. First, we calculate the value of EVR. Such as the confidence level is 95%, the value of EVR of the emergy value is 6.30E+21. Secondly, we evaluate the risk index of Gansu's ecosystems. Finally, we evaluate the estimated value of ecosystem services at risk, when the given emergy value is 4.00E+21 sej, the estimated value is 0.6685. It means that the probability of the emergy value at risk in next year bigger than 4.00E+21 sej is 0.6685.