| As the life support system, ecosystem is providing a range of services for human well-beings. Since the term "ecosystem services" was put forward in 1983, a wide range of studies associated with ecosystem services theory and valuation has been carried out, which has been enhancing public understanding of the importance of the ecosystem. The valuation of ecosystem services has become an essential tool to tell the importance of ecosystem for humans, and also a scientific basis for cost-benefits analysis and trade-off in resource management aim to meet more effective policy-making.Based on the reviews on the progress towards ecosystem services studies and the valuation practices, this paper firstly analysis and define what ecosystem services are. According to the various scales the ecosystem services are generated, and based on the classification method of ecosystem services giving by other scholar, this thesis firstly discuss the classifications and valuation indexes of regional ecosystem services, then a GIS-based approach for valuation and mapping of ecosystem services at mesoscale is developed, which is applied to a case study in Tiantai County, Zhejiang Province.The main content and results are as follows:The relationships among "nature components-ecosystem processes-ecosystem functions-ecosystem services-benefits" are discussed. Ecosystem services refers to the products, processes and functions that can be enjoyed, consumed and utilized to satisfy human needs, directly or indirectly. Ecosystem services are an ecological phenomenon, which are generated from ecosystem processes and functions for satisfying human needs and increasing well-beings.Based on the understanding on the ways ecosystem provides benefits, the ecosystem services are subdivided into provisioning services, regulating services, cultural services and supporting services including 31 kinds of services. To avoid double-counting, ecosystem services are divided into intermediary services and final services, and a kind of valuation-oriented indexes are discussed. A GIS-based approach and/or framework for ecosystem services valuation is discussed to overcome some of obstacles in revealing the spatial difference of ecosystem, enabling the progress towards distributing the values toward each grid. The framework contains four key steps: study area definition, data collection and data-base establishment, calculation and value assignment, ecosystem services value mapping.The GIS-based approach is applied to value the ecosystem services of Tiantai County in 2005, the results indicate that the total ecosystem services value(TEV) is 0.87 times of the GDP, direct use value(DV) is a little higher than indirect use value(IDV). The forest ecosystem occupies the highest percentage of TEV in Tiantai County, and the river ecosystem occupies the lowest. The mapping results show a high degree of spatial heterogeneity, however, the TEV and the value per unit area of each administrative unit doesn't show one to one relationship. The townships in central basin occupy the higher percentage of TEV, whereas the forest areas in northeast Tiantai County occupy higher value per unit area. It shows that the using the value per unit area as an indicator is more practical to reveal the protection of ecosystem and the environmental pressure.The related verification results show the significant competitive relationship between forest and farmland. The increase of forest area can significantly enhance the indirect use value; the increase of farmland area can significantly enhance the products provisioning services value, while at the same time weaken the benefits obtain from indirect use value. It is a positive correlation among each kind of indirect use value of ecosystem services, but a negative one between each direct use value. Further studies are required to get deep insights to generate new regional perspectives on key ecosystem services protection.
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