Experimental evaluation of the impact of a payment for environmental services program on deforestation

Abstract

Despite calls for greater use of randomized control trials (RCTs) to evaluate the impact of conservation interventions; such experimental evaluations remain extremely rare. Payments for environmental services (PES) are widely used to slow tropical deforestation but there is widespread recognition of the need for better evidence of effectiveness. A Bolivian nongovernmental organization took the unusual step of randomizing the communities where its conservation incentive program (Watershared) was offered. We explore the impact of the program on deforestation over 5 years by applying generalized additive models to Global Forest Change (GFC) data. The “intention‐to‐treat” model (where units are analyzed as randomized regardless of whether the intervention was delivered as planned) shows no effect; deforestation did not differ between the control and treatment communities. However, uptake of the intervention varied across communities so we also explored whether higher uptake might reduce deforestation. We found evidence of a small effect at high uptake but the result should be treated with caution. RCTs will not always be appropriate for evaluating conservation interventions due to ethical and practical considerations. Despite these challenges, randomization can improve causal inference and deserves more attention from those interested in improving the evidence base for conservation.

Statistical matching for conservation science

“…; Wiik et al. ). More commonly, where this is not possible or desirable, good practice should be to explore and consider potential controls using matching from as early as possible.…”

“…; Wiik et al. ). However, methodological advances to improve causal inference from nonexperimental data have helped to better attribute conservation impacts (Ferraro & Hanauer ).…”

In-kind conservation payments crowd in environmental values and increase support for government intervention: A randomized trial in Bolivia

“…Between the 1960s and early 2000s, deforestation in the Bolivian lowlands increased from about 4.7x10 4 hectares/year to more than 2.9x10 5 hectares/year (Killeen et al 2008). During the ten years prior to our baseline survey, deforestation in our specific study area was approximately 4,147hectares, with a mean deforestation rate of 1.2% per community (Wiik et al 2019). The goal of the Watershared program was to limit forest degradation, as well as deforestation.…”

“…Pynegar et al (2018) examined the impact of the intervention on water quality (in terms of E. coli contamination of water used for human consumption) and found no impact. Wiik et al (2019) showed that the intervention had limited impact on slowing deforestation (using the Global Forest Change data).…”

Exploratory and confirmatory research in the open science era

“…Strict experiments in applied ecology (Box 1) are generally conducted at small spatial scales (although there are some notable exceptions, e.g. Krebs, Boutin & Boonstra 1995;Wiik et al 2019). This contrasts the fact that many ecological and policy processes operate at far larger scales (Estes et al 2018).…”