This thesis examines the challenges and potential consequences of use of the economical method stated preference in valuation of ecosystems services. For the purpose of internalizing the externalities of the market that is causing degradation of biodiversity and ecosystems, the UN initiative The Economics of Ecosystems and Biodiversity is striving to create political initiative for nature conservation by highlighting the economic value of ecosystem services. There are though difficulties incorporating the ethical dimension of the question of nature conservation into this approach. In opposition to the preference-based valuation method ecological economists argues that we, instead of maximizing the fulfillment of individual preference, must set limitations for economic growth if we are to solve the challenges of degradation of biodiversity. Both approaches do seek to push political decisionmakers, and nature conservation is therefore for the most part a political question.