- Date: 10 March 2022
- Author: Craig Beatty, Manager, Forests Research & Strategy, WWF
For millions of us, a walk in the woods changed from a pastime to a necessity during this pandemic. It’s about as safe and socially distanced as can be, and access to forests has often helped ease my mind. After being indoors for days on end, forests became a place where I could escape and unwind. Spending time in forests makes me feel better. But what’s the science behind that, and could forests be doing more for our health?
Before the pandemic, WWF started asking how forests benefit human health. During the fall of 2019, we hosted a Fuller Symposium on human health and conservation that heavily featured forests’ contributions to our well-being. We heard a lot of statements about how forests and human health might influence each other but not much that provided a more holistic view of the type of forest and health research that exists or how to start classifying it.
With this in mind, we redoubled our efforts to understand the science behind forests and human health. Our investigation explored five categories of potential interactions between forests and human health: noncommunicable diseases like cancer and diabetes, environmental exposure, food and nutrition, physical hazards, and infectious diseases. The results of our investigation are detailed in our new report published today, The Vitality of Forests: Illustrating the Evidence Connecting Forests and Human Health.
We uncovered ample evidence that forests provide, prevent and heal. While there are some hazards forests pose to human health, we found that the conservation, protection and restoration of the world’s forests are undeniably critical to safeguarding and promoting human health while also making indispensable contributions to managing climate change and biodiversity loss.
Importantly, the role climate change plays in human health is woven throughout this report. We know that our exposure to physical hazards like heat and more severe storms and floods will increase and the habitat of common vectors of infectious diseases like mosquitoes and ticks will expand. We also know the nutritional content of staple foods will decrease as CO2 in our atmosphere increases. And we know that people are more vulnerable to climate change if their health is already compromised. For each of these impacts, forests represent an indispensable solution to mitigating and adapting to climate change while also supporting the health and well-being of people.
One interesting example that emerged in the report was the role of forests in heat and humidity. Anyone who has experienced a hot day knows the value of a shady tree, but urban forest cover that exceeds 40% per city block has the largest cooling potential, and forest cover in rural areas has similar cooling potential.[2,3] This is especially relevant for people who work outside or in places without air conditioning. However, in the face of crushing heat waves like those in the Pacific Northwest and Argentina, forests do more than provide shade and cooling potential. As humidity approaches 100% with an air temperature of 95 degrees Fahrenheit (35 degrees Celsius), the human body reaches its physiological limit for expelling heat — sweat no longer works — and people are unable to survive without cooling technology. Research demonstrates that the circulation of air from forest transpiration, or the evaporation of water from plants during photosynthesis, keeps humidity from reaching 100% and can provide our bodies with the ability to expel more heat than we create.
While forests have the capacity to support human health and well-being, their existence doesn’t guarantee positive human health outcomes; there are lots of unhealthy people in areas with great forests. What we learned was that forests’ contributions to human health are strongly impacted by environmental, institutional and behavioral factors as well as mediating factors that allow or prohibit people from realizing the health benefits of forests.
Influencing forests’ ability to benefit human health will require actions that transcend the conservation and public health domains. The conservation sector must value and champion how forest protection, management and restoration improve human health and partner with the public health sector to better integrate the role healthy forests play in our lives. This includes protecting forests and avoiding their conversion; improving forest management in working lands; taking a diversified approach to forest restoration; and creating urban forests.
It also means conservation must recognize and promote the role public health can play in supporting forest conservation, protection and restoration and seek public health input and solutions that cooperatively address conservation goals. Concurrently, we need to understand the cause-and-effect relationships between forests and human health. Sometimes poor human health drives forest loss — where deforestation can provide people with money to pay for medical procedures or funeral expenses. In other situations, the loss of forests leads or compounds serious human health impacts that can ripple through families and communities.
In The Vitality of Forests, we present a holistic framework that connects forests and human health. If applied, this framework will ultimately lead to better conservation and public health outcomes. But this isn’t just a framework meant for the pages of a report. It is intended to better justify why the public, policymakers and private sector should be interested in forests’ role beyond their recreational, carbon sequestration, or biodiversity conservation potential.
The evidence demonstrates that public health and forests are entwined — at the local, regional and global scale — and that across each of nature’s contributions to human health, forest conservation, protection and management can improve human lives. And when we consider the public health challenges we face in our communities, counties and countries, we should examine the very real health implications of how we’re treating our forests — and how they’re treating us.
 Brauman, K. A., Garibaldi, L. A., Polasky, S., Zayas, C., Aumeeruddy-Thomas, Y., Brancalion, P., DeClerck, F., Mastrangelo, M., Nkongolo, N., Palang, H., Shannon, L., Shrestha, U. B., and Verma, M. (2019). Chapter 2.3. Status and Trends – Nature’s Contributions to People (NCP).
In: Global assessment report of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Brondízio, E. S., Settele, J., Díaz, S., Ngo, H. T. (eds). IPBES secretariat, Bonn, Germany. 76 pages DOI: 10.5281/zenodo.3832035
 Ziter, C.D., Pedersen, E.J., Kucharik, C.J. & Turner, M.G. (2019). Scale-dependent interactions between tree canopy cover and impervious surfaces reduce daytime urban heat during summer. Proceedings of the National Academy of Sciences, 116, 7575–7580. DOI: 10.1073/pnas.1817561116
 Wolff, N. H., Masuda, Y. J., Meijaard, E., Wells, J. A., & Game, E. T. (2018). Impacts of tropical deforestation on local temperature and human well-being perceptions. Global Environmental Change, 52, 181–189. DOI: 10.1016/j.gloenvcha.2018.07.004
 Tuholske, C., Caylor, K., Funk, C., Verdin, A., Sweeney, S., Grace, K., et al. (2021). Global urban population exposure to extreme heat. Proceedings of the National Academy of Sciences, 118. DOI: 10.1073/pnas.2024792118