Peer Review Report For: The impacts of Payment for Ecosystem Services programmes on health and wellbeing: a systematic review protocol [version 1; peer review: 1 approved]

Background Payment for Ecosystem Services (PES) programmes are being implemented worldwide to encourage the maintenance of sustainable and healthy ecosystems, with some of them part of the carbon offsetting market and carbon capture strategies developed to reduce carbon emissions. However, their impacts on health, health inequalities and wellbeing remain unclear. This systematic review aims to assess the health and subjective wellbeing impacts on individuals/communities who are incentivised to protect their environments. Methods We will search the databases EconLit, Medline, CAB Abstracts® and Global Health® via Web of Science, GreenFILE, International Initiative for Impact Evaluation (3ie) and grey literature from World Health Organisation (WHO), Food and Agriculture Organisation (FAO), and World Bank. Studies will be eligible for inclusion if they are assessing PES, a health or subjective WB outcome, and have a comparator group (including different levels of the intervention). Abstracts and full text articles will be assessed independently by two researchers. Risk of bias will be assessed using ROBINS-I for quantitative studies and CASP for qualitative studies. For quantitative data we will do random-effects meta-analysis to estimate pooled effect sizes where possible. For the qualitative data we will report people's experiences of PES and potential mechanisms through which health impacts arise using content analysis. Effect heterogeneity across differing forms of implementation, sociodemographic characteristics and contexts will be explored. We will refine our provisional logic model to incorporate insights from the quantitative and qualitative data. Certainty of evidence will be assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. Conclusions This review will provide the first synthesis of the health and subjective wellbeing impacts of PES programmes, helping to understand the potential for market-based policies to achieve environmental and health co-benefits. We anticipate reporting findings in peer-reviewed publications, conference presentations and through briefings to policymakers and community leaders.