Deforestation is a major cause of biodiversity loss, and the largest factor driving deforestation is expansion of agriculture. Payments for Ecosystem Services (PES) are a voluntary market based strategy envisioned to protect threatened ecosystems. However, implementing PES is challenging mainly because of adverse self-selection –which ultimately results in investing payments to protect land that was at low risk of being lost without PES. This project will be the first to assess potential mechanisms driving adverse self-selection of a national-level PES, in the world’s most endangered eco-region, and work with policy-makers to incorporate results into national-level policies in Argentina.