Abstract: Ecosystem services and the natural capital stocks that produce them are critical to the functioning of the Earth′s life supporting system. They contribute to human welfare, both directly and indirectly, and therefore represent part of the total economic value of the planet. Four scientific quastions about the functions of ecosystem services are discussed in this paper. They are: 1) study of the integration, amount and spatial location of functions of ecosystem services; 2) the spatial transfer of functions of ecosystem services; 3) the relationship between ecosystem service and ecological security; and 4) the sustainable use of ecosystem services. The heterogeneity in the structure of ecosystem's results in heterogeneity of their functions. Consequentially, there is spatial heterogeneity in the functions of ecosystem services. Thus, it is necessary to analyze the functions of ecosystem services by qualitative, quantitative and spatial means. Some functions of ecosystem services can be transferred spatially by various methods, and produce benefits at areas far removed from their habitats and range of suitable conditions. This phenomenon is called spatial transfer of ecosystem services. Thus, characteristic ecosystem services can bring economic values to a region of larger area than that covered by the ecosystem′s habitats. Ecosystem services provide supporting system for humans, and their strengths depend on ecological capital stock. Ecological capital stock illustrates the capability of sustainable development of a country. Ecological capital stock of an ecosystem relies in turn on the function and the structure of the ecosystem. Endangerment of ecosystem service raises a question for ecological security. In many regions ecological resources are rare. To use ecological resources sustainably, local communities should be urged to develop their economies by means of managing ecosystem services, i.e., to industrialize the management of ecosystem services. These four scientific questions for ecosystem services are related to each other. The aim of discussing them is to focus study on ecosystem services in the future.

Key words: Rhinopithecus bieti, geographical distribution, population size, ecology, conservation