A team led by a public health professor used CDC data on 40,307 adults and satellite maps of tree cover to study every census block in the United States. They tested whether higher residential tree canopy relates to lower allostatic load, which measures the body's cumulative wear and tear from chronic stress.
Overall results showed that greater tree cover was generally associated with lower allostatic load. However, the association did not hold for the most vulnerable groups. The expected health benefits were clear for people with higher income and education who were employed, but absent for less-advantaged people.
The pattern was similar for non-Hispanic white and Hispanic groups, but different for non-Hispanic Black participants. The researchers point to other environmental and social stressors — discrimination, lack of good job opportunities, and poor neighborhood conditions — that may limit the calming effects of trees. They conclude that urban greening is valuable but must be paired with policies to address social and economic root causes.
Difficult words
- allostatic load — body's long-term physical effects of chronic stress
- tree cover — trees and leaves that cover land near homes
- canopy — upper layer of leaves and branches of treesresidential tree canopy
- vulnerable — at higher risk because of difficult conditions
- discrimination — unfair treatment of people for personal traits
- urban greening — adding green spaces and trees in cities
- root cause — main social or economic reasons for a problemroot causes
- advantaged — having more resources or better social positionless-advantaged
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Discussion questions
- Would planting more trees in your neighborhood help people's health? Why or why not?
- What social or economic policies could be paired with urban greening to help vulnerable groups?
- Have you noticed differences in green space in different parts of your city? How might that affect residents' stress?
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