Industrialization and modernization of the $20^{th}$ century have brought convenience to human life. However, such development produced unintentional global environmental issues such as destruction of natural ecosystem through excessive use of the natural environment beyond its capacity. The United National (UN) recognized such global environment issues and coordinated with worldwide experts to conduct a comprehensive assessment of the global ecosystem, "Millennium Ecosystem Assessment (MA)", to resolve the issues. The UN conducted the MA primarily to comprehend the correlation between the ecosystem and human welfare. The results demonstrated that the ecosystem provides various direct and indirect benefits to human. This new concept was introduced as the "ecosystem services". Introduction of the ecosystem services highlighted the significance of the ecosystem and led to increased research and active discussions among experts from various discipline over the recent 10 years. It has been considered that the ecosystem service concept could be incorporated in policymaking process, as primary criteria to assess and weigh the benefits of using natural resources against the effects on value of the ecosystem. The current policymaking process is affected by the contradicting logics of modernization and preservation of ecosystem. The ecosystem services concept could be the answer to forming a rational policymaking process, allowing for nature preservation while wisely using the available natural resources. The general consensus has been formed on the need of incorporating the ecosystem services concept in the policies and globally various researches on the ecosystem services have been actively conducted. However, introduction of the ecosystem services concept is still at a very early stage and research on real application of the ecosystem services is yet almost nonexistent. Also there are no clear and agreed definition, classification scheme and value appraisal methodology regarding the ecosystem services. Therefore, this research explains the basic concept of the ecosystem services and highlights specific issues for further researches, as further researches on real application of the ecosystem services would find ways for the ecosystem services approach to be valuable in the policymaking process.