Valuing ecosystem services using benefit transfer: Separating credible and incredible approaches
Ecosystem goods and services are now widely recognized as the benefits that humans derive from the natural environment around them including abiotic (e.g. atmosphere) and biotic components. The work by Costanza et al. (1997) to value the world’s ecosystem services brought the concept of ecosystem service valuation to the attention of the world press and environmental economists working in the area of non-market valuation. The article’s US \$33 trillion estimate of these services, despite world GDP being only US \$18 trillion, was definitely headline grabbing. This ambitious effort was undertaken with reliance on transferring existing values per unit from other (often site specific) valuation studies. Benefit transfer (see Boyle and Bergstrom, 1992; Rosenberger and Loomis, 2000, 2001) involves transfers of values per unit from an area that has been valued using primary valuation methods such as contingent valuation, travel cost or hedonic property methods (Champ et al., 2003) to areas for which values are needed. Benefit transfer often provides a reasonable approximation of the benefit of unstudied ecosystem services based on transfer of benefits estimates per unit (per visitor day, per acre) from existing studies. An appropriate benefit transfer should be performed on the same spatial scale of analysis (e.g. reservoir to reservoir, city to city) as the original study. However, the reasonableness of benefit transfer may be strained when applying locally derived per acre values from studies of several thousand acres of a resource such as wetlands to hundreds of millions of acres of wetlands.