This multi-country project aims to establish the health benefits of large-scale land restoration in Africa's Sahel region. We will leverage the Great Green Wall (GGW) of Africa initiative, the largest land restoration effort in the world, as a natural experimental system. Drylands host nearly 40% of the global population. The GGW and other similar land-restoration efforts currently underway around the world are set to reshape landscapes and the lived experiences of billions of people globally. Such restoration efforts are increasingly being regarded as potential 'Nature-based solutions' as the world seeks to confront and adapt to the triple challenges of climate change, biodiversity loss and food security. At present however, human health considerations play a very minor role in the design and implementation of restoration projects, including the GGW. This project aims to fill this critical gap, to ensure restoration projects can maximally serve human health alongside other objectives. We will use a novel combination of activities spanning 4 integrated work packages to do this. Briefly, WP1 will comprise a literature review and community consultations to develop an iteratively refined, gender-sensitive logic model describing the causal linkages between dryland restoration and human health. This will guide the project by helping to refine key hypotheses and identify a suitable subset of secondary health outcomes to be evaluated in subsequent WPs. In WP2 we will collate as much existing data as possible for GGW countries to conduct a Sahel-wide village-matched health impact evaluation. The primary outcome to be investigated will be weight-for-age z score (WAZ) of children (0-59 months) as a measure of acute nutritional status. A subset of secondary outcomes in children and women emerging from WP1 as of particular relevance will also be considered. We will compare health outcomes between communities with and without GGW activities to evaluate the health impacts of restoration. WP3 will be a follow-up of WPs1-2 in which we will conduct a more targeted, community-prioritised, village-matched health impact evaluation with primary data collection in three focal countries (The Gambia, Senegal, Burkina Faso). Based on our current understanding of the linkages between health and environmental restoration, these are likely to include other anthropometric measures (e.g., height-for-age z score, HAZ), and outcomes reflecting risk factors on the nutrition, infection and mental health / well-being pathways. We will again focus on children and non-pregnant women. Some secondary outcomes require collection of biological samples from children for laboratory analysis. Follow-up sampling will give information on seasonal effects and an opportunity to compare child growth over a 12-14 month period between groups with and without GGW interventions. WP4 comprises a set of integrating tasks aimed at marrying the results of the health impact evaluations with current activities guiding the design and implementation of the GGW and understanding the role of and benefits to health of completing the GGW. With an anticipated cost of around $50 billion to reach its 100 million hectare target of restored drylands by 2030, it is essential for health impacts (benefits and costs) to be brought into existing decision-support tools for applied purposes. We will do this via a combination of steps from health economic evaluation, cost-benefit and trade-off analysis, and systems and scenario modelling in the context of a changing climate. In all WPs, our Project Partners and Scientific Steering Committee will further ensure local relevance and streamline the research-to-practice pipeline, enhancing impact.