A theoretical model for assessing the sustainability of ecosystem services

The Value of the World’s Ecosystem Services and Natural Capital by Costanza in 1997 is generally re-garded as a monument for the research of valuing ecosystem services. However, the classif ication of ecosystem ser-vices, the method of various services summation and the purpose for static global value had be confronted by many criticisms. Based on the summary of these criticisms, suggestions, related function assessment and further study direction, the sustainability of ecosystem services is presented. The two basic indicators in ecology, productivity and biodiversity, respectively charactering the ability of producing and self-organizing, not only represent the internal function of ecosystem, but also are proportioned to its external function of supporting and providing for human life. On presenting the general form of ecosystem services assessment, this paper improves the mathematical formula by giving a function adjusting coeff icient composed of productivity and biodiversity. Theoretically, the integration of the two indicators reflects the changes of ecosystem services at spatial and temporal scales, can physically assess the sustainability of ecosystem services, and build a f irm scientif ic fundament of value assessment for ecosystem services. Objectively, its application should be strictly tested in next step.