More damaged trees mean fewer ecosystem benefits for low-income residents

Maya Mangala-Munuma '25 first noticed it in her hometown of Grand Rapids, Michigan. When she walked from an affluent neighborhood to a more impoverished one, not only the houses and demographics changed. The trees did, too.

"You go from a really nice neighborhood with big, gorgeous, established trees, and then there's essentially a line where all of a sudden the trees don't look the same," Mangala-Munuma said. "I wanted to know why and if it's actually a phenomenon."

She pursued the question for her undergraduate honors thesis at Cornell and is now first author of the resulting study, published in Urban Forestry & Urban Greening on Sept. 17, that finds a wide discrepancy in tree health along socioeconomic lines across 29 U.S. cities.

Using public data on representative city plots, Mangala-Munuma and her team found that, on average, 17% of trees were damaged in the whitest, most affluent neighborhoods, compared to nearly 60% in impoverished, racially diverse neighborhoods. The trees in minority neighborhoods also had 7% fewer leaves and were more likely to be dead.

"This is a pretty striking finding, and it's not just one city - it's across all of them," said senior author and Mangala-Munuma's adviser Daniel Katz, assistant professor in the School of Integrative Plant Science in the College of Agriculture and Life Sciences (CALS). "We know that trees do a great job of things like cooling, keeping people out of emergency rooms during heat waves. What this work implies is that people who are most vulnerable and most need these services are the least likely to receive them."

Previous research using aerial images had documented that lower income, minority neighborhoods have fewer trees than more affluent, whiter areas, but this is the first study to account for the health of those trees, which greatly impacts the benefits they provide.

"If you're just looking top-down at how many trees there are, you're going to miss the fact that these trees are also going to perform differently based on how damaged they are," said Mangala-Munuma, who majored in plant science in CALS. "Not all trees are created equal."

A healthy, mature tree provides cooling and shade, reduces air pollutants and catches stormwater; previously researchers have found that a lack of trees and the associated ecosystem services has resulted in tens of thousands of doctor's visits and hundreds of deaths. Damaged trees provide those benefits to a lesser extent or not at all, and can be hazardous, with branches or even entire trees at risk of falling.

The research team used data from the Urban Forest Inventory & Analysis program, which provided on-the-ground assessments of 23,659 trees in 3,166 representative plots in the 29 cities. They paired that with demographic, economic and housing data from the U.S. Census Bureau's American Community Survey.

With Mangala-Munuma's study documenting the pattern broadly, Katz and his lab are now using satellite data to zero in on the health of individual trees, so that rather than extrapolating from representative plots, researchers and stakeholders can see exactly which trees are damaged.

"The study shows us this pervasive pattern in tree condition and mortality. Now we want to be able to say, here are all the individual trees that are at risk," Katz said.

While the study doesn't address the causes for the discrepancy, Katz said one big factor is likely the lower rates of homeownership in poorer and more racially diverse neighborhoods, as homeowners have more incentive to plant and care for trees.

"This work is somewhat related to the literature on the effects of redlining and the fact that the Home Owners' Loan Corporation was more likely to provide loans to whiter, more affluent individuals," Katz said. "Even though the practices of redlining haven't been in operation for many decades, those legacies persist."

Mangala-Munuma, now a research administrator at Van Andel Institute, a biomedical research institute in Grand Rapids, hopes the study can alert residents and even city parks and recreation departments to a new site of inequality - one that could be remediated.

"It's absolutely a problem that in the future can be addressed," she said. "But it starts with knowing the problem exists."

The study was a first opportunity for Mangala-Munuma to feel ownership of a project from start to finish and was an education in persistence and adaptability. The research team had to change course several times based on the availability of data and the ongoing analyses.

"Dan really encouraged me to not see those changes as failures or mistakes," Mangala-Munuma said. "This is just how the research process works: As you're doing the project, you learn something new about it, and that's going to change your initial direction."

Katz said the project started with Mangala-Munuma's interests and her ambition to study something with a real-world impact. "And she had the motivation to see it through," Katz said. "I count myself as fortunate to have worked with her on this project."

Raising awareness of the issue, and seeing people's interest and concern has been the biggest reward, Mangala-Munuma said.

"If you're just walking on the street, it might be something you feel without thinking about it," she said. "Now it's something you can go out and see."

Co-authors include Eli Robinson, MPS '23; Sarah R. Young, associate professor of social work research in medicine, and Dr. Arnab Ghosh both at Weill Cornell Medicine; postdoctoral researcher David L. Miller; as well as Alexander Young from the University of New Hampshire, Wenna Xi from Northwestern University and Chenghao Wang from the University of Oklahoma.