Three approaches to estimating REDD costs can be identified in the literature (Boucher 2008):
1. Local-empirical models.
2. Global-empirical approaches.
3. Global simulation models.
Sometimes these approaches are simply grouped into local and global models.²
Estimates from local-empirical models are based on detailed studies (surveys) in a particular area. Both the per-area cost estimates ($/ha) and the carbon density estimates (ton/ha) are specific to the particular region studied, and the division of per-area opportunity costs by carbon density gives the opportunity costs on a perton basis (Boucher 2008). Since results are specific to a particular region, their extrapolation or generalisation can be problematic...