The climate gains of urban trees
From stormwater runoff prevention to reducing the impacts of extreme heat, tree canopies provide a host of health and climate resiliency benefits for those in urban landscapes.
Why it matters: Not all trees are distributed equally. A new Climate Central analysis reveals which localities nationwide benefit most from the boons of urban forests.
How it works: Urban tree coverage helps reduce the impacts of extreme heat, prevents stormwater runoff, mitigates air pollution exposure and can even sequester carbon, per the analysis.
- A tree's leaves can absorb pollutants like ozone and nitrogen dioxide, the report noted.
What they found: The U.S. cities with the most air pollution absorbed by trees are Presque Isle, Maine; Eugene, Ore.; Eureka, Calif.; Bangor, Maine; and Duluth, Minn., according to Climate Central data shared with Axios.
- By contrast, the cities with the most intense urban heat islands are Houston, New Orleans, Newark, New York City and San Francisco.
Zoom in: Only about 18% of Houston is currently covered by tree canopy, with a roughly 14% "tree cover discrepancy" between high and low-income neighborhoods, reports the Houston Chronicle.
What they're saying: Jaime González, Community and Equitable Conservation Programs Director for the Nature Conservancy's Texas Chapter, tells Axios the city of Houston is working to meet an "ambitious" goal of 4.6 million trees planted by the year 2030.
- González' team just partnered with the Texas A&M Forest Service to map available planting zones in Gulfton, Texas — a "nature-deprived" neighborhood in Houston that's home to a largely immigrant and lower-income community. They estimated 804 trees could be placed there to increase tree canopy cover.
- "You just walk around the neighborhood, there are long, long stretches where there are no trees and it's just hot pavement," says González. (In 2020, parts of Gulfton were 17 degrees hotter in the afternoon than the city's coolest neighborhood, per the Washington Post.)
- "If there's a very large pot of money coming down, there needs to be equitable and empowering ways to get the money to the communities that are going to be served."
State of play: The Inflation Reduction Act provided $1.5 billion in funding over 10 years to the U.S. Forest Service’s Urban and Community Forestry Program.
- Beattra Wilson, assistant director for cooperative forestry at the U.S. Forest Service, tells Axios in an email that the IRA funding will allow them to "reach more communities to help plant, replace, and maintain millions of trees."
- Wilson also notes the agency's focus on "equity considerations" and prioritizing "underserved communities" with the funding, which will be allotted through grants through 2031.
Zoom out: Historic redlining, a discriminatory housing practice, has led to higher proportions of racial minorities living in areas with less tree canopy cover, which can exacerbate health problems, per a 2021 study.
- Plus, reports by D.C.-based nonprofit Casey Trees find that communities in Wards 5, 7, and 8 — home to the largest percentage of Black and Latino residents — have seen the highest rates of tree canopy loss over the last five years.
- "These communities can experience flooding, extreme temperatures due to heat island effects, and higher rates of respiratory issues," Casey Trees' Vincent Drader tells Axios in an email.
The intrigue: Kelvin Fong, assistant professor at Dalhousie University and an environmental health and justice researcher, tells Axios that the racial and social determinants that drive inequities in tree cover are not just an “urban greening problem,” but a “health equity issue."
- "If you just take the health records of people over a large area, and you trace their health outcomes, you will find that those who live in areas of higher green space or tree canopy cover tend to have better health outcomes," says Fong.
Yes, but: "Tree for tree, [urban] trees are potentially doing a lot. But it's not going to offset the fossil fuels which are also concentrated in cities," says Lucy Hutyra, professor of earth and environment at Boston University.
- From planting costs to maintenance, she notes the costliness of urban trees, as well as the different growing environments city to city, which produces varying ecosystem services and benefits.
The bottom line: "Trees are part of the solution," Hutyra tells Axios. "But they are not the whole solution."
Axios' Simran Parwani contributed reporting to this story.