Effectiveness of the Costa Rican Payments for Ecosystem Services program in mitigation of greenhouse gas emissions: Trends in carbon stocks 2012-2020

Payments for ecosystem services (PES), a mechanism of incentives or compensation to landowners for provision of ecosystem services, have grown as a tool for meeting conservation goals. The Costa Rican payments for ecosystem services (PSA) program is one of the best-known examples because of being one of the most established. Despite this, the PSA program and many other PES programs do not monitor the provision of ecosystem services directly, as they are not simple to measure and quantify and resources to systematically monitor them may not be available. This study uses maps of carbon stocks in Costa Rica, created based on REDD+ land cover maps and carbon densities, in conjunction with a database of almost 8,000 PSA program contracts for years 2012-2020, to explore trends in carbon stocks in the program. Each PSA program goal, priority area, and contract type explored in this study was associated with either higher carbon stocks or change in carbon stocks than the goals or baselines that they were being compared to. In spatial targeting, all priority areas were more carbon dense than non-priority areas, but protected areas, indigenous territories, and conservation importance were most effective at targeting areas of higher carbon density. In contract types, forest protection and forest management contracts had higher carbon densities at the beginning of the contracts than baselines, while agroforestry systems, reforestation, mixed systems, natural regeneration, and forest management contracts had higher rates of increase in carbon stocks than baselines. Scenarios that resulted in low carbon densities or growth rates may reflect tradeoffs with other ecosystem services or with other goals of the program. Assessment of other ecosystem services and program goals could help improve program design.