Tree Canopy Health Is Not Shared Equally, Study Finds

A new national study complicates a long-standing assumption about tree canopy health: that more green space automatically translates into better health for everyone nearby. Led by Michigan State University public health researcher Amber Pearson and published in The Lancet Regional Health-Americas in May 2026, the research matched health records from 40,307 adults with satellite maps of tree cover for census blocks across the United States. Denser residential canopy was linked to lower allostatic load, the cumulative wear and tear chronic stress leaves on the body, but the link held only for higher-income, employed, and more highly educated adults. For less-advantaged groups, it vanished, according to Medical Xpress, which reported on the findings.

"Our study found that the benefits of trees are not equally experienced," said Pearson, a professor in MSU's College of Human Medicine. The pattern held for non-Hispanic white and Hispanic participants, but not for non-Hispanic Black participants. Strikingly, the gap was not explained by a lack of trees: 24% of non-Hispanic Black participants lived in high-canopy neighborhoods, yet showed none of the reduction in stress-wear seen in other groups. Pearson's team also found indications that part of the benefit flows through physical activity, suggesting leafy streets encourage movement, but not equally for everyone.

How researchers tied tree canopy health to stress biology

The team used CDC health data and satellite imagery covering every census block in the country, making it one of the broadest examinations of neighborhood greenery and stress physiology to date. Allostatic load captures the physiological cost of chronic stress, strained cardiovascular, metabolic, and immune systems, which over time raise the risk of chronic disease. The national scope is what makes the unequal pattern so hard to dismiss: the same canopy that tracked with healthier stress profiles in affluent blocks showed no such relationship in disadvantaged ones. "Trees are not a panacea," Pearson said.

Pearson cautions against reading the results as a reason to stop planting. Her explanation, in plain terms: for some groups, other stressors, unfair treatment, unstable work, poor neighborhood conditions, may simply drown out nature's calming effects. In other words, the trees may be working, but the rest of life is working harder. The study's core question, whether tree canopy health is truly a public good, now has a harder answer. That framing turns greening into a necessary but insufficient step, a counterpoint to campaigns that treat canopy coverage as a finish line rather than a starting point. Future research, she said, needs to untangle which stressors blunt the benefit.

What greener cities still deliver for everyone

A separate June 2026 study underscores why cities keep planting even as the health picture grows murkier. Researchers found that urban parks cut heat, air pollution, and noise not just inside their borders but hundreds of meters beyond them, according to Phys.org. Tree cover and grassland reduced felt temperature, physiologically equivalent temperature, a measure of how hot conditions feel to the human body, by as much as 8.5 degrees Celsius compared with nearby built-up streets. "Our work shows that parks can bring measurable cuts in heat, pollution and noise both inside parks and across surrounding neighborhoods," said Professor Prashant Kumar. The cooling, in other words, appears close to universal; the stress-biology payoff is not.

Getting trees into the ground, and keeping them alive, is its own challenge. In a large field experiment in Dayton, Ohio, researchers planted 640 native saplings across 20 parks and tested irrigation methods through a growing season. About 48% survived to season's end, with red maple, northern catalpa, and honey locust consistently outlasting white oak, black gum, and sassafras, according to Ohio State University. "People don't necessarily think of how their yard connects to the surrounding environment, but we all contribute to the urban forest by planting in our own space," said Erika Wright, the study's first author. The takeaway for planners: planting is the beginning, not the end.

What this means for your neighborhood's greening plans

If your city announces a tree-planting blitz, the research suggests asking what comes with the saplings: watering schedules, maintenance budgets, species matched to local conditions, and residents involved in the planning. Canopy alone, the MSU study implies, cannot compensate for the chronic stressors that fall hardest on disadvantaged blocks, unfair treatment at work, precarious jobs, under-resourced streets. Pairing greening with those deeper fixes is the equity argument: trees as one ingredient in healthier neighborhoods, not a substitute for one. Readers can follow more coverage of urban forests and planting efforts on GenZ NewZ's plants and trees topic page, including South Africa's drive to plant a billion trees.

None of this means trees are a bad bet. The same body of research keeps confirming that canopy cools streets, cleans air, and, for many people, eases the body's stress load. What the May 2026 study adds is a demand for honesty about who captures those gains. As Pearson put it, the benefits of trees are not equally experienced, and closing that gap will take more than planting. It will take tending the social soil, too.