The study, led by Amber Pearson of the Michigan State University College of Human Medicine and published in Lancet Regional Health–Americas, linked Centers for Disease Control and Prevention records for 40,307 adults with satellite-derived maps of tree canopy and analyzed results at the census-block level. The researchers examined whether higher residential tree cover was associated with lower allostatic load, the cumulative ‘‘wear and tear’’ the body suffers from chronic stress.
Findings showed that, overall, greater tree canopy tended to correspond with lower allostatic load. But the association was not uniform across social groups. People with higher income and education who were employed showed clear health benefits from nearby trees, while less-advantaged people did not. Results were similar for non-Hispanic white and Hispanic subpopulations; they differed for non-Hispanic Black participants. The paper notes that 24% of non-Hispanic Black participants lived in high-canopy neighborhoods yet did not show the same reduction in allostatic load.
The authors argue that other environmental and social stressors — such as discrimination, limited job opportunities, and poor neighborhood conditions — can override or limit the positive effects of nature. They conclude that urban greening can be a valuable public health tool, but it must be accompanied by policies that address the root causes of social and economic inequality, otherwise health gains from trees may not reach the most vulnerable people.
Difficult words
- tree canopy — layer of leaves and branches over the ground
- allostatic load — the body's accumulated stress-related damage
- cumulative — built up over a period of time
- satellite-derived — created using information from satellites
- census-block — small geographic unit used for population data
- override — to prevent or cancel the effect of something
- urban greening — planting and caring for plants in cities
- vulnerable — at greater risk of harm or disadvantage
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How could cities combine urban greening with social policies to help the most vulnerable residents?
- Why might non-Hispanic Black participants not show the same reduction in allostatic load even in high-canopy neighborhoods? Give possible social or environmental reasons from the article.
- What practical challenges do you think city planners face when trying to bring more tree cover to disadvantaged neighborhoods?
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