In 2015, the UN adopted 17 Sustainable Development Goals (SDGs), aiming to "protect the planet from degradation…so that it can support the needs of the present and future generations".1UNTransforming our world: the 2030 agenda for sustainable development. United Nations, New York2015Google Scholar Through the SDGs, the UN recognises that conservation directly supports human health and wellbeing by providing goods like water and fibre, and global public goods like habitat for species and mitigation of climate change.1UNTransforming our world: the 2030 agenda for sustainable development. United Nations, New York2015Google Scholar, 2Myers SS Gaffikin L Golden CD et al.Human health impacts of ecosystem alteration.Proc Natl Acad Sci USA. 2013; 110: 18753-18760Crossref PubMed Scopus (268) Google Scholar Although trade-offs can indeed arise between conservation and economic development, the Rockefeller Foundation–Lancet Commission on planetary health3Whitmee S Haines A Beyrer C et al.Safeguarding human health in the Anthropocene epoch: report of The Rockefeller Foundation-Lancet Commission on planetary health.Lancet. 2015; 386: 1973-2028Summary Full Text Full Text PDF PubMed Scopus (1122) Google Scholar states unequivocally that "the environment has been the foundation of human flourishing", suggesting that if environmental degradation persists then ongoing improvements in human health are likely to be reversed. The increasing availability of data and improved analytical techniques now enable better understanding of where environmental conditions and human health are tightly linked, and where investing in nature can deliver net benefits for people—especially with respect to the most vulnerable populations in developing countries. These advances bring more opportunities for interventions that can advance multiple SDGs at once. We have harmonised a suite of global datasets to explore the essential nexus of forests, poverty, and human health, an overlap of SDG numbers 1, 2, 3, 6, and 15. Our study combined demographic and health surveys for 297 112 children in 35 developing countries with data describing the local environmental conditions for each child (appendix).4Herrera D Ellis A Fisher B et al.Upstream watershed condition predicts rural children's health across 35 developing countries.Nat Commun. 2017; 8: 811Crossref PubMed Scopus (49) Google Scholar This allowed us to estimate the effect forests might have in supporting human health, while controlling for the influence of important socio-economic differences.4Herrera D Ellis A Fisher B et al.Upstream watershed condition predicts rural children's health across 35 developing countries.Nat Commun. 2017; 8: 811Crossref PubMed Scopus (49) Google Scholar We extended this work to look at how forests affect three childhood health concerns of global significance for the world's poorest people: stunting, anaemia, and diarrhoeal disease. We found that, for the poorest households in these 35 countries, forest cover is associated with reduced prevalence of all three childhood maladies, after controlling for potential confounding variables (eg, education, and rainfall; figure). Among children in the two lowest wealth quintiles, those who live in areas with more forest cover were significantly less likely to have these diseases than those living in areas with less forest cover. For children in the two highest wealth quintiles, in contrast, we found no relation between forest cover and any of these health outcomes. We also found that as the amount of upstream forest cover increases, the benefits for the poor increase, particularly for those poor households without access to improved water sources (appendix). These findings suggest that the poorest populations are least capable of replacing natural capital with technology or infrastructure, and are therefore disproportionately affected by the degradation of natural ecosystems. The particular mechanisms through which forest cover can positively affect health outcomes appear to vary among contexts and diseases,5Pattanayak S Wendland K Nature's Care: diarrhea, watershed protection, and biodiversity conservation in Flores, Indonesia.Biodivers Conservation. 2007; 16: 2801-2819Crossref Scopus (43) Google Scholar, 6Trask JR Kalita PK Kuhlenschmidt MS Smith RD Funk TL Overland and near-surface transport of Cryptosporidium parvum from vegetated and nonvegetated surfaces.J Environ Qual. 2004; 33: 984-993Crossref PubMed Google Scholar, 7Bauch SC Birkenbach AM Pattanayak SK Sills EO Public health impacts of ecosystem change in the Brazilian Amazon.Proc Natl Acad Sci USA. 2015; 112: 7414-7419Crossref PubMed Scopus (61) Google Scholar and gaining a deeper understanding of these causal mechanisms will be critical in making effective environmental or health interventions.2Myers SS Gaffikin L Golden CD et al.Human health impacts of ecosystem alteration.Proc Natl Acad Sci USA. 2013; 110: 18753-18760Crossref PubMed Scopus (268) Google Scholar, 3Whitmee S Haines A Beyrer C et al.Safeguarding human health in the Anthropocene epoch: report of The Rockefeller Foundation-Lancet Commission on planetary health.Lancet. 2015; 386: 1973-2028Summary Full Text Full Text PDF PubMed Scopus (1122) Google Scholar Nonetheless, the positive signal we get from forests in these analyses is notable, given that the combined global effects of diarrhoea, anaemia, and stunting on the world's children are devastating and the world's forests are steadily disappearing. Diarrhoeal disease is the second leading cause of childhood mortality globally, killing more children than malaria, AIDS, and measles combined.8WHOThe Countdown to 2015: maternal, newborn, and child survival. World Health Organization, Geneva2010Google Scholar Iron-deficiency anaemia, the most common form of anaemia, has a role in 20% of maternal deaths.7Bauch SC Birkenbach AM Pattanayak SK Sills EO Public health impacts of ecosystem change in the Brazilian Amazon.Proc Natl Acad Sci USA. 2015; 112: 7414-7419Crossref PubMed Scopus (61) Google Scholar Childhood stunting affects over 160 million children worldwide, often limiting physical and cognitive growth for life.8WHOThe Countdown to 2015: maternal, newborn, and child survival. World Health Organization, Geneva2010Google Scholar Investing in ecosystem conservation, restoration, or both, might not only improve childhood health outcomes across much of the developing world where forests are in decline, but also help to weaken the poverty-health trap in which many of the world's poorest people find themselves. The forest–human health connection described here is only one example of the relation among nature, poverty, and human health. Other empirical studies have quantified relations between fisheries decline and nutrient deficiencies,9Golden CD Allison EH Cheung WW et al.Fall in fish catch threatens human health.Nature. 2016; 534: 317-320Crossref PubMed Scopus (344) Google Scholar between deforestation and malaria,9Golden CD Allison EH Cheung WW et al.Fall in fish catch threatens human health.Nature. 2016; 534: 317-320Crossref PubMed Scopus (344) Google Scholar and between bushmeat availability and anaemia.10Golden CD Fernald LCH Brashares JS Rasolofoniaina BJR Kremen C Benefits of wildlife consumption to child nutrition in a biodiversity hotspot.Proc Natl Acad Sci USA. 2011; 108: 19653-19656Crossref PubMed Scopus (217) Google Scholar Given the strong associations among well-functioning ecological systems, poverty, and human health, a critical area of research is understanding how natural resource management and conservation can advance multiple SDGs. Clearly understanding these relations is not an easy task. The database we built took over 3 years to build, clean, and operationalise. The complexity of the nature–human health relationship necessitated deep thinking around our theoretical models to control for factors that confound these relations and reflect the differentiated effects of local versus regional environmental processes. Nonetheless, it must become a routine for governments, aid agencies, and other organisations investing in economic development to use the data now available to minimise trade-offs, and to seek co-benefits among environmental health, human health, and equity outcomes. This work was supported by the National Socio-Environmental Synthesis Center (SESYNC) under funding from the National Science Foundation DBI-1052875; The Gordon and Betty Moore Foundation and The Rockefeller Foundation as part of the Health and Ecosystems: Analysis of Linkages (HEAL) programme. CDG was supported by the Wellcome Trust's Our Planet, Our Health program [106964MA] and the National Science Foundation Coupled Natural Human Systems grant 1826668. In memory of Diane Adams. We declare no competing interests. Download .pdf (.48 MB) Help with pdf files Supplementary appendix