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.
Policies must balance forest conservation’s local costs with its benefits—local to global—in terms of biodiversity, the mitigation of climate change, and other eco-services such as water quality. The trade-offs with development vary across forest locations. We argue that considering location in three ways helps to predict policy impact and improve policy choice: (i) policy impacts vary by location because baseline deforestation varies with characteristics (market distances, slopes, soils, etc.) of locations in a landscape; (ii) different mixes of political-economic pressures drive the location of different policies; and (iii) policies can trigger ‘second-order’ or ‘spillover’ effects likely to differ by location. We provide empirical evidence that suggests the importance of all three considerations, by reviewing highquality evaluations of the impact of conservation and development on forest. Impacts of well-enforced conservation rise with private clearing pressure, supporting (i). Protection types (e.g. federal/state) differ in locations and thus in impacts, supporting (ii). Differences in development process explain different signs for spillovers, supporting (iii).
Protected areas (PAs) dominate conservation efforts. They will probably play a role in future climate policies too, as global payments may reward local reductions of loss of natural land cover. We estimate the impact of PAs on natural land cover within each of 147 countries by comparing outcomes inside PAs with outcomes outside. We use ‘matching’ (or ‘apples to apples’) for land characteristics to control for the fact that PAs very often are non-randomly distributed across their national landscapes. Protection tends towards land that, if unprotected, is less likely than average to be cleared. For 75 per cent of countries, we find protection does reduce conversion of natural land cover. However, for approximately 80 per cent of countries, our global results also confirm (following smaller-scale studies) that controlling for land characteristics reduces estimated impact by half or more. This shows the importance of controlling for at least a few key land characteristics. Further, we show that impacts vary considerably within a country (i.e. across a landscape): protection achieves less on lands far from roads, far from cities and on steeper slopes. Thus, while planners are, of course, constrained by other conservation priorities and costs, they could target higher impacts to earn more global payments for reduced deforestation.