Trees for Human Health & Wellness

Kathleen Wolf Kathleen Wolf
University of Washington

Research on the relationships of nature experiences in cities and human health has been underway for decades. In recent years the number of studies has surged, providing important insights. Nearby nature is not just nice to have, it is profoundly important for the wellness of people and their communities.

The studies address a wide range of health outcomes. They show a clear pattern. Access to nature, from views out the window to brief outdoor walks, benefit people at all phases of the human life cycle, from cradle to grave.

The studies vary in the type of nature experience that contributes to health response. Conditions or interventions include general vegetation distribution, parks, gardens, and campuses. Studies also explore responses to the urban forest, including canopy, street trees, immersive experiences in groves or natural areas, and forest bathing.

Our international team of scientists has prepared a review of the city trees and health outcomes1 . Here are some of our discoveries.

Across the thousands of articles about nature and health we settled on about 200 peer-reviewed publications that focus on city trees. Our review started with consideration of strength of evidence. In public health and medical research there is a recognized range of science quality, with randomized controlled trials being the gold bar (Figure 1).

Strength of Evidence is based on how research is designed

Then we sorted the tree-focused studies by health outcomes and science quality. We first found a range of studies that indicate how tree and forest experiences can be used as treatment or therapy for diagnosed health concerns (Figure 2). In other words, these are fairly direct health responses.

Current evidence about trees and treatments or therapies for human health.




The second set of studies describe the ‘protective’ health influences of trees and forests ( Figure 3). Our nation and communities are seeing a rise in chronic diseases, such as diabetes, high blood pressure, and stress responses. In the terms of public health, protective influences help people to avoid chronic disease or ease severity and treatment costs.

The ‘protective’ health influences of trees and forests




For both treatment and protective influences of trees, we sorted the study outcomes by strength of evidence. In some instances, strength of evidence decisions were based on study method, in others the interpretation was based on there only being a small number of studies.

Why is this information important? You may have opportunities to engage public health or medical professionals as non-traditional partners in tree planning and programs. Rather than making simple sweeping claims about trees and health, you can talk with more confidence about the range of studies and health outcomes. Current research is exploring dosage, and even planning principles for tree planting that can enhance health.2 We continue to learn ever more about why Trees Are Good!

Please visit the Green Cities: Good Health website for additional information about the health benefits of trees and nearby nature for people and communities.


1. Adapted from a presentation at the Partners in Community Forestry conference (November 2019) and a literature review: Wolf, K.L., S. Lam, J. McKean, G. Richardson, M. van den Bosch, A.C. Bardekjian. (in review). Urban trees and human health: A scoping review.

2. Barron, S., S. Nitoslawski, K.L. Wolf, A. Woo, E. Desautels, S.R.J. Sheppard. 2019. Greening blocks: A conceptual typology of practical design interventions to integrate health and climate resilience co-benefits. International Journal of Environmental Research and Public Health 16, 4241.