Valuing nature: From environmental impacts to natural capital

Economic valuation of natural and environmental assets is now a well established practice. Economic analysis provides several methods for discovering the impact on social welfare associated with changes in the ability of these assets to provide different goods and services. In general terms, these valuation exercises have been performed in the framework of Environmental Impact Assessment or, more generally, Cost Benefit Analysis. There is, however, an increasing demand nowadays to go beyond this framework and to value natural capital (natural resource stocks, land and ecosystems) as such. There are two main reasons for this new demand. On the one hand, sustainability requires that proper account should be taken of capital depreciation and, therefore, there is a need to value natural capital changes. This valuation process, nevertheless, only makes sense when some kind of substitution between natural and other forms of capital is allowed. On the other hand, there is also an increasing tendency to demand that the stock of natural capital present in a given territory be valued, either to discover one of the main components of social wealth or to help adequately plan changes in land use. Yet, whereas conventional valuation methods are probably adequate to fulfill the first task, this is less true in the case of the second, while even more difficulties arise in connection with the third one. Even if at first sight the process appears conceptually identical, these tasks are of a different order of magnitude, as the experience of both the World Bank and the Statistics Division of the United Nations in this respect clearly shows.