Valuing the invaluable: how much is the planet worth?

This article explores the valuation of natural capital by critically analysing alternative approaches to it. It considers the problems associated with applying economic values to natural capital and the limitations of such exercises. It examines different methods that are more familiar to accountants than economists of using what is sometimes termed an engineering approach' to estimating the costs of maintaining and restoring existing assets. It considers the arguments that are used to justify the two. In particular, it addresses the question of what we are seeking to do by determining the value of natural capitalwhat is the question to which valuation is supposed to be the answer?