Trees are good for us. They clean the air of sulfur dioxide, carbon monoxide, and particulates, and release oxygen for us to breathe. Researchers have shown how trees cut down on the rate of breathing-related illnesses and therefore save thousands of lives a year.
Now a new study from the USDA Forest Service, Drexel University, and the University of North Carolina provides further evidence of the value of trees. It shows that when trees go away, people suffer higher rates of cardiovascular disease.
The new paper, published in the journal Health & Place, looks at the impact of the emerald ash borer (EAB) in Detroit using data from the Women’s Health Initiative, a large women’s health survey. It shows that women in EAB-ravaged areas had 25% higher rates of “acute myocardial infarction,” ischemic and hemorrhagic stroke, or death from coronaries.
For researchers, it’s normally hard to know if a person is unhealthy because there are fewer trees or because of a host of other related factors, such as income, education, race, and the neighborhoods where they live. From an experimental point of view, the outbreak of EAB is useful because trees are affected equally across districts, irrespective of the people living there.
“Taking into account all research, not just my own, I’d say that there is strong, but not definitive, evidence linking trees and improved public health,” says lead researcher Geoffrey Donovan in an email.
The research should add to the case for maintaining and improving urban tree canopies (something that’s actually been happening quite a bit anyway).
Asked how many trees we should plant, Donovan says: “I imagine that there is an upper limit [to the number of trees we need], but I think we’re a long way from that point.”