Health experts and urban planners have long believed that planting more trees in residential areas is good for everyone in those neighborhoods.
A new study shows that’s not necessarily so.
Researchers at Michigan State University found that while trees do reduce stress and extend longevity, the benefits vary based on other factors.
Professor Amber Pearson led the study. She and her team examined the relationship between residential tree canopies and allostatic load. That’s the cumulative wear-and-tear that stress has on the human body. Pearson says they confirmed that trees improve human health.
“What we found was that having higher percentage of residential trees was associated with lower allostatic load scores,” she says. “In other words, it’s good for your health.”
But Pearson found something surprising: It wasn’t good for everyone.
Researchers used federal health data on 40,000 people across the country. They also looked at satellite data from tree canopies in about 10 million U.S. census tracts.
Pearson says health benefits varied based on things like education, income, and employment.
“We found a relationship in those that were more socioeconomically advantaged, but not the more vulnerable or disadvantaged participants,” she says.
The study found that Hispanic and non-Hispanic white participants saw significant improvement, while non-Hispanic Black participants did not.
Pearson says social and economic stress may override nature’s health benefits.
“Trees alone may not be enough to overcome those stressors in those populations,” she says. “We really need to do more to understand those stressors and that’s an area of future research.”
Pearson says the findings could challenge people’s assumptions about trees.
“Trees are not a panacea,” she says.
The study appears in the Lancet Regional Health – Americas.
This story is a part of WDET’s on-going series, The Detroit Tree Canopy Project.
