In this pioneering study, Krutilla and Fisher put the amenity resources of natural environments into an analytical framework comparable to that for the extractive resources. The models and theoretical background of their techniques are illustrated by case studies which include the controversial Hells Canyon dam, the Mineral King ski resort, and the Trans-Alaska pipeline.The authors point out that resource development activities undertaken on public lands often receive financial advantages---preferential tax treatment, subsidized capital, and access to public resources---that are not taken into account in the costs of the project. True evaluation of the costs and benefits of a development project often tips the balance in favor of preserving an area in a natural state.