  Carbon offsets from voluntarily avoided deforestation projects are generated
based on performance vis-\`a-vis ex-ante deforestation baselines. We examined
the impacts of 27 forest conservation projects in six countries on three
continents using synthetic control methods for causal inference. We compare the
project baselines with ex-post counterfactuals based on observed deforestation
in control sites. Our findings show that most projects have not reduced
deforestation. For projects that did, reductions were substantially lower than
claimed. Methodologies for constructing deforestation baselines for
carbon-offset interventions thus need urgent revisions in order to correctly
attribute reduced deforestation to the conservation interventions, thus
maintaining both incentives for forest conservation and the integrity of global
carbon accounting.
