The world’s forests provide valuable contributions to people but continue to be threatened by agricultural expansion and other land uses.Counterfactual-based methods are increasingly used to evaluate forest conservation initiatives. This review synthesizes recent studies quantifying the impacts of such policies and programs.Extending past reviews focused on instrument choice, design, and implementation, our theory of change explicitly acknowledges context. Screening over 60,000 abstracts yielded 136 comparable normalized effect sizes (Cohen’s d). Comparing across instrument categories, evaluation methods, and contexts suggests not only a lack of “silver bullets” in the conservation toolbox, but that effectiveness is also low on average. Yet context is critical. Many interventions in our sample were implemented in “bulletproof” contexts of low pressure on natural resources. This greatly limits their potential impacts and suggests the need to invest further not only in understanding but also in better aligning conservation with local and global development goals.
We estimate neighbor interactions in deforestation in Costa Rica. To address simultaneity and the presence of spatially correlated unobservables, we measure for neighbors’ deforestation using the slopes of neighbors’ and neighbors’ neighbors’ parcels. We find that neighboring deforestation significantly raises the probability of deforestation. Policies for agricultural development or forest conservation in one area will affect deforestation rates in non-targeted neighboring areas. Correct estimation of the interaction reverses the naive estimate’s prediction of multiple equilibria.
Even a perfect measure of the ecosystem services provided by each parcel enrolled in a PES program would be insufficient to measure the overall effectiveness of the program. The simple reason is that if a PES program does not lead to an increase in the provision of ecosystem services compared to what would have happened in the absence of the program—that is, the baseline or “counterfactual”—then it has not accomplished anything. Imagine a PES program focused on forest conservation that makes payments to managers of ecologically rich forest land, who have no incentive to clear the land because it is illsuited for logging, agriculture, or urbanization. Payments to these managers would have little impact on deforestation because the risk of clearing was minimal to begin with. In contrast, payments to managers who have incentives to clear their land would be much more likely to have an impact.