What influences the effectiveness of forest conservation interventions in tropical regions? A systematic review

Recent decades have witnessed a proliferation of forest conservation interventions in tropical developing countries. Impact evaluations most frequently report that these interventions have statistically significant but modest effects on deforestation. As forest loss has persisted, understanding how to improve intervention effectiveness has become an important empirical question. We systematically reviewed counterfactual-based studies examining heterogeneous impacts of forest conservation interventions. We focus on two dimensions of heterogeneity: (1) design and implementation features that generate variation in treatment, and (2) contextual factors that moderate treatment effects. From an initial pool of 1,739 studies, we identified 58 relevant papers, highlighting an emerging but still limited body of evidence. The literature on heterogenous impacts is heavily skewed toward protected areas (63% of studies) and, to a lesser extent, payments for ecosystem services (15%), leaving many intervention types underexamined. On the design and implementation side, most studies compared “multiple-use” versus “strict” protected areas but found no consistent ranking, reinforcing the view that the most effective design of protected areas is context-dependent. A smaller set of studies points to the importance of management capacity and collaborative governance arrangements. On the context side, the largest number of studies examined variation by deforestation pressure and development potential, indicating a pervasive pattern: interventions tend to be more effective where threats – and thus potential additionality – are higher. We conclude by drawing methodological lessons from existing heterogeneity analyses and calling for further impact evaluations that move beyond average effects and focus on policy-relevant sources of variation.