Health benefits of trees
Recent studies have shown that sometimes, going to a park, or even looking a single tree can significantly improve a person’s health and stress levels. Some doctors have started prescribing parks as a remedy to patients’ health issues, and our tree values have been expanded to include mental and physical health benefits. While this is intuitive to tree lovers, seeing these studies can help us communicate the value of trees more.
Air quality and climate mitigation
Our trees are critical in filtering our air, removing harmful pollutants, such as Carbon Monoxide (toxic at high levels), particulate matter (causes asthma), and Ground-level Ozone (various respiratory impacts). See the image on the right.
As previously discussed in our stormwater post, trees filter drinking water for us and the creatures with which we share the world.
A less-reported value of trees are their mental health benefits, but these can outweigh many of the others, shown through many studies (links below):
- Improved memory
- Reduced hospital time and improved recovery, from a view of green or treed space
- Increased attention level in children
- Increase social cohesion of communities
Heat is one of the greatest impact on urban health, and trees, through shade and transpiration, can greatly reduce heat-related illness and comfort. Trees can reduce ambient heat by up to 9 degrees Fahrenheit, compared to exposed areas.
The folklore of trees providing hiding spots for crime is largely negated by modern research, which shows trees can greatly improve crime statistics in neighborhoods. Controlled for social background, areas with vegetation and healthy trees performed much better than unvegetated areas. In one study, vegetated areas had 7 to 8 percent less gun-related incidents than the control area. This most likely links with the mental health benefits of trees, but is good to take into account when planning a city.
Our community’s trees overall health benefits
Our i-Tree study provides us with actual number values of some of these benefits, and in Arlington, our trees provide us with the following health benefits:
- Number of trees: 755,400 (45 trees/acre, a healthy natural forest has 40-60 trees/acre)
- Pollution removal: 235 tons/year ($3.59 million/year)
- Carbon storage: 204,000 tons ($27.1 million)
- Carbon sequestration: 9,630 tons/year ($1.28 million/year)
- Avoided stormwater runoff: 10,730,168 cubic feet/year ($717 thousand/year)
- Building energy savings: $1,020,000/year
- Avoided carbon emissions: 2,210 tons/year ( $294,000/year)
These numbers take into account avoided hospital visits, illness, and death, and show how trees can really improve ourselves and our community!
- Prescribing a trip to the park instead of the pharmacy (Washington Post Article: https://www.washingtonpost.com/national/health-science/why-one-dc-doctor-is-prescribing-walks-in-the-park-instead-of-pills/2015/05/28/03a54004-fb45-11e4-9ef4-1bb7ce3b3fb7_story.html
- Trees are good for your health (Washington Post Article): https://www.washingtonpost.com/news/energy-environment/wp/2015/07/09/scientists-have-discovered-that-living-near-trees-is-good-for-your-health/
- Scientific American report on trees and mental health: https://www.scientificamerican.com/article/does-being-around-trees-help-people-feel-good/
- EPA guidance on reducing heat island effect in urban areas with trees: https://www.epa.gov/heat-islands/using-trees-and-vegetation-reduce-heat-islands
- Forest Service research on trees and air quality: https://www.nrs.fs.fed.us/units/urban/local-resources/downloads/Tree_Air_Qual.pdf
- Yale study on crime reduction and trees: http://environment.yale.edu/envy/stories/trees-shed-bad-wrap-as-accessories-to-crime