Fewer Credits, More Credibility: jurisdictional baselines in REDD+ provide more conservative, and appropriate, estimates of avoided deforestation.

Abstract

Reducing emissions from deforestation and forest degradation (REDD+) projects can mobilise crucial finance for tropical forest conservation through the sale of carbon credits. The first generation of REDD+ methodologies used historical deforestation rates from reference areas to predict deforestation in the absence of the REDD+ intervention, establishing the project’s baseline scenario ex-ante. Carbon credits were issued based on the difference between the baseline scenario and the deforestation observed in the project area. However, independent academic studies using ex-post quasi-experimental methods reported that many REDD+ projects had used baseline scenarios that overestimated business-as-usual deforestation, leading to substantial over-issuance of carbon credits. The research contributed to a scandal which wiped $1bn off the value of Voluntary Carbon Markets. Verra, the world’s largest accreditor of carbon credits, has since launched VM0048, a REDD+ methodology which uses jurisdictional rather than project-level data to calculate ex-ante baselines. However, to date, there are no studies that have assessed whether VM0048 produces more appropriate baselines (judged by agreement with ex-post quasiexperimental methods) compared to the now inactive first-generation methodologies. Here, we retrospectively apply the VM0048 methodology to a set of REDD+ projects in Colombia which have been assessed using ex-post quasi-experimental methods. Results show VM0048 baselines are on average 80% (ranging from 59% to 94%) more conservative than those from the now inactive first-generation REDD+ methodologies, and forecasts of avoided deforestation closely align with independent ex-post quasi-experimental assessments of project effectiveness. Nonetheless, important caveats remain. Most importantly, VM0048 ex-ante baselines fundamentally cannot account for unexpected deforestation rates not reflected in historical trends. Whilst divergence between methods is inevitable, VM0048 ultimately remains constrained by the limitations of any ex-ante framework. Our results, although specific to the Colombian context, therefore represent cautious optimism for the next generation of REDD+ projects: we find that the methodological refinements in VM0048 produce more conservative baselines, yet the exante design could continue to facilitate systematic over- and under- estimated baselines in REDD+ globally.

Date of Award	15 Sept 2025
Original language	English
Supervisor	Julia Patricia Gordon Jones (Supervisor), Eleanor Warren-Thomas (Supervisor) & Katie Devenish (Supervisor)