Description

Excerpt: PES has many attractive characteristics relative to other conservation approaches provided that transaction costs are low and other favorable conditions apply (see sections 2 and 3 of this Sourcebook). However, ascertaining PES s advantages requires measuring the effect of actual programs in the field. Such impact evaluation can also help in identifying opportunities for further improvements in efficiency of these programs and looking out for other environmental services that can find ready markets.

The technical and social complexities of payment for environmental services make impact analysis challenging. Spatial interlinkages, difficulty of perceiving environmental services, the long gestation of benefits, and the multiple objectives of some PES efforts all complicate matters. Many impact studies are therefore either anecdotal or based on a small sample size. Studies that only include PES participants in their sample tend to suffer from selection bias. Further, only some studies have access to baseline information, while many others depend on recall method. This can lead to incorrect inferences about the impact of a PES initiative. The objectives of this brief is to suggest some ways of doing impact evaluation studies that can adequately reflect what is going on in the field. This section begins with a quick review of what impact studies should measure.