Can We Afford to Conserve Biodiversity?

Recent studies have highlighted the potentially enormous economic losses due to the degradation of biological diversity (Heywood 1995, Daily 1997). Environmental goods and services provided by natural biological systems have been valued at between 2. 9 trillion and 33 trillion annually (Costanza et al. 1997, Pimentel et al. 1997), although some of these goods and services may depend more on biomass than on biological diversity per se (Myers 1996, Hector et al. 1999, Tilman 1999), it seems very likely that biodiversity itself is worth several trillion dollars a year. In contrast, the costs of maintaining biodiversity have received rather less comment, and few reliable figures are available (Pimentel et al. 1997). Estimates range from 680 million to 42 billion (UNEP 1992), clustering around 20 billion (IUCN/UNEP/WWF 1991, WCMC1992, WRI/IUCN/UNEP 1992). However, the data and assumptions underlying these estimates are generally unclear. To improve the empirical basis and precision of these estimates, we set out a sequence of steps for global biodiversity conservation and computed their costs based on new data and published figures. Our estimates of the costs of global conservation, while high, are considerably less than government expenditures on environmentally harmful subsidies.