To my knowledge, the literature so far does not formally define PES, which contributes to some conceptual confusion. For our field work in Bolivia and Vietnam, we used five relatively simple criteria to describe the PES principle. A PES is:
1. a voluntary transaction where
2. a well-defined ES (or a land-use likely to secure that service)
3. is being ‘bought’ by a (minimum one) ES buyer
4. from a (minimum one) ES provider
5. if and only if the ES provider secures ES provision (conditionality).
First, PES is a voluntary, negotiated framework, which distinguishes it from command-and-control measures. This presupposes that potential ES providers...