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We develop a theory of change for payments for environmental services (PES) to review their imminent strengths and weaknesses in light of a growing body of impact evaluation studies. We show that PES are probably at least as environmentally additional as other conservation tools, based on the limited evidence. The original vision of PES as being direct, flexible, and potentially effective remains valid, but PES design and implementation have to be upgraded in their economic functioning to better realize this potential. Adverse self-selection, inadequate administrative targeting, and ill-enforced conditionality constitute three key obstacles that may considerably hamper PES success. Policies such as spatial targeting to service density, threat and cost levels, and payment differentiation can alleviate the design challenges. PES site selection needs to further move into high-threat areas. Making adequate PES design choices also requires the political will to boost environmental effects.

An important part of conservation practice is the empirical evaluation of program and policy impacts. Understanding why conservation programs succeed or fail is essential for designing cost‐effective initiatives and for improving the livelihoods of natural resource users. The evidence we seek can be generated with modern impact evaluation designs. Such designs measure causal effects of specific interventions by comparing outcomes with the interventions to outcomes in credible counterfactual scenarios. Good designs also identify the conditions under which the causal effect arises. Despite a critical need for empirical evidence, conservation science has been slow to adopt these impact evaluation designs. We identify reasons for the slow rate of adoption and provide suggestions for mainstreaming impact evaluation in nature conservation.

We estimate the early effects of the pilot project to Reduce Emissions from Deforestation and forest Degradation (REDD+) in the Brazilian Amazon. This project offers a mix of interventions, including conditional payments, to reduce deforestation by smallholders who depend on swidden agriculture and extensive cattle ranching. We collected original data from 181 individual farmers. We use difference-in-difference (DID) and DID-matching approaches and find evidence that supports our identification strategy. We estimate that an average of 4 ha of forest were saved on each participating farm in 2014, and that this conservation came at the expense of pastures rather than croplands. This amounts to a decrease in the deforestation rate of about 50%. We find no evidence of within-community spillovers.

Tropical forests continue to be plagued by the dual sustainability challenges of deforestation and rural poverty. We seek to understand why many of the farmers living in the Brazilian Amazon, home to the world’s largest tropical agricultural-forest frontier, persist in agricultural activities associated with low incomes and high environmental damage. To answer this question, we assess the factors that shape the development and distribution of agricultural activities and farmer well-being in these frontiers. Our study utilizes a uniquely comprehensive social-ecological dataset from two regions in the eastern Brazilian Amazon and employs a novel conceptual framework that highlights the interdependencies between household attributes, agricultural activities, and well-being. We find that livestock production, which yields the lowest per hectare incomes, remains the most prevalent land use in remote areas, but many examples of high income fruit, horticulture, and staple crop production exist on small properties, particularly in peri-urban areas. The transition to more profitable land uses is limited by lagging supply chain infrastructure, social preferences, and the fact that income associated with land use activities is not a primary source of perceived life quality. Instead subjective well-being is more heavily influenced by the nonmonetary attributes of a rural lifestyle (safety, tranquility, community relations, etc.). We conclude that transitions away from low-income land uses in agricultural-forest frontiers of the Brazilian Amazon need not abandon a land-focused vision of development, but will require policies and programs that identify and discriminate households based on a broader set of household assets, cultural attributes, and aspirations than are traditionally applied. At a broader scale, access to distant markets for high value crops must be improved via investments in processing, storage, and marketing infrastructure.

Assessing global tendencies and impacts of conditional payments for environmental services (PES) programs is challenging because of their heterogeneity, and scarcity of comparative studies. This meta-study systematizes 55 PES schemes worldwide in a quantitative database. Using categorical principal component analysis to highlight clustering patterns, we reconfirm frequently hypothesized differences between public and private PES schemes, but also identify diverging patterns between commercial and non-commercial private PES vis-à-vis their service focus, area size, and market orientation. When do these PES schemes likely achieve significant environmental additionality? Using binary logistical regression, we find additionality to be positively influenced by three theoretically recommended PES 'best design' features: spatial targeting, payment differentiation, and strong conditionality, alongside some contextual controls (activity paid for and implementation time elapsed). Our results thus stress the preeminence of customized design over operational characteristics when assessing what determines the outcomes of PES implementation.

We assess the additional forest cover protected by 13 rural communities located in the southern state of Chiapas, Mexico, as a result of the economic incentives received through the country's national program of payments for biodiversity conservation. We use spatially explicit data at the intra-community level to define a credible counterfactual of conservation outcomes. We use covariate-matching specifications associated with spatially explicit variables and difference-in-difference estimators to determine the treatment effect. We estimate that the additional conservation represents between 12 and 14.7 percent of forest area enrolled in the program in comparison to control areas. Despite this high degree of additionality, we also observe lack of compliance in some plots participating in the PES program. This lack of compliance casts doubt on the ability of payments alone to guarantee long-term additionality in context of high deforestation rates, even with an augmented program budget or extension of participation to communities not yet enrolled.

Cameroonian community forests were designed and implemented to meet the general objectives of forest management decentralization for democratic and community management. The spread of management conflicts all over the country has shown that these broad expectations have not been met. We describe conflicts occurring in 20 community forests by types of actors and processes involved. We argue that a number of external (community vs. external actors) and internal (intra-community) conflicts are part of the causes blocking the expected outcome of Cameroonian community forests, fostering bad governance and loss of confidence. Rent appropriation and control of forest resources appear as systemic or generalized conflicts. While community forest support projects have tended to focus on capacity building activities, less direct attention has been given to these systemic problems. We conclude that some factors like appropriate leadership, and spending of logging receipts on collective benefits (direct and indirect) are needed to minimize conflicts. Government and development agencies should concentrate efforts on designing concrete tools for improving financial transparency while privileging communities with credible leaders.

The PLOS ONE Collection \"Measuring forest conservation effectiveness\" brings together a series of studies that evaluate the effectiveness of tropical forest conservation policies and programs with the goal of measuring conservation success and associated co-benefits. This overview piece describes the geographic and methodological scope of these studies, as well as the policy instruments covered in the Collection as of June 2016. Focusing on forest cover change, we systematically compare the conservation effects estimated by the studies and discuss them in the light of previous findings in the literature. Nine studies estimated that annual conservation impacts on forest cover were below one percent, with two exceptions in Mexico and Indonesia. Differences in effect sizes are not only driven by the choice of conservation measures. One key lesson from the studies is the need to move beyond the current scientific focus of estimating average effects of undifferentiated conservation programs. The specific elements of the program design and the implementation context are equally important factors for understanding the effectiveness of conservation programs. Particularly critical will be a better understanding of the causal mechanisms through which conservation programs have impacts. To achieve this understanding we need advances in both theory and methods.

Agri-food social-ecological systems (AFSES) embrace complex interactions and processes of food production, processing, and commercialization that are subject to constant changes. This study develops a heuristic approach using the adaptive cycle (AC) and a transformation potential measure to identify the historical trajectory of a coffee AFSES at a watershed scale in Copalita, Mexico, over 40 years from 1980 to 2020. Primary information was collected through semistructured interviews. The results show that the system interactions depend on economic, social, and environmental stressors and shocks affecting different temporal and spatial scales. The cumulative effects of driving forces and adaptive strategies have influenced the system to not complete the AC phases. Additionally, the results show that some adaptive strategies can become new stressors with time. Driving forces, adaptive strategies, tipping points, trade-offs and interactions within the AFSES could be identified as the main aspects defining system resilience.

In complex Social-Ecological Systems (SES), the interplay between ecological and social components shapes trajectories that impact human well-being and ecosystem services. While SES dynamics have been studied in static conditions, there has been less attention to how said systems respond to shocks and stressors over time and space. This special issue presents a collection of articles that use diverse methodologies—ranging from system dynamics modeling to participatory approaches—to analyze past SES changes and discuss future scenarios. Case studies from regions including Brazil, Colombia, Mexico, Honduras, Chile, Ethiopia and Mongolia illustrate key variables influencing social–ecological transitions and provide insights into potential policy strategies to support sustainable SES. The studies underscore the need for multi-scalar approaches to SES research that explicitly theorize and empirically assess trajectories across space and time.