The importance of biodiversity valuation is widely understood in academia and is increasingly used in policy making and other fora. For example, the Convention on Biological Diversity (CBD), through the Conference of the Parties (COP), recognises that "economic valuation of biodiversity and biological resources is an important tool for well-targeted and calibrated economic incentive measures". Further, it encourages the Parties to "take into account economic, social, cultural and ethical valuation in the development of relevant incentive measures" (CBD COP Decision IV/10). Biodiversity valuation should be an integral part of environmental economic policy, providing information to policy makers in their quest to identify priorities and equate trade-offs. As part of its effort to support governments in using valuation methods to assess the value of biological diversity, the OECD commissioned this series of case studies. They cover the state of the art on economic valuation and on the interface between economic and ecological valuation.