Making a difference takes time: assessing the impact of Colombian public land acquisitions on forest cover in the Andes

Emily French, Ana Reboredo Segovia, Paulo Arévalo , Christoph Nolte 

Public land acquisitions (PLAs) are a promising conservation instrument, combining the permanence of protected areas with the voluntary, compensatory structure of payments for ecosystem services, yet causal evidence on their effectiveness remains limited. Colombia’s Article 111 mandate, which requires departments to allocate 1% of revenue to land acquisition for watershed protection, has produced one of the world’s largest and longest-running PLA programs, enabling rigorous evaluation. We estimate the impact of 2,512 PLAs in the Colombian Andes on parcel-level forest cover from 2001 to 2021 using covariate matching and staggered difference-in-differences. PLAs have a statistically significant, time-accumulating effect on forest cover, increasing from 0.16 percentage points after one year of protection to 2.53 percentage points after 15 years. Effects are driven primarily by forest regrowth rather than avoided deforestation, consistent with program targeting and active reforestation on acquired parcels. Benchmarking against the literature, estimated effect sizes fall within the range reported for protected areas and payments for ecosystem services. These results indicate that PLAs can generate measurable conservation gains even when implemented in relatively low-threat landscapes. Crucially, impacts emerge slowly and accumulate over time, implying that evaluations based on short post-treatment windows will systematically underestimate their effectiveness.