Urban forests have massive benefits—they help combat heat-island effect and aid stormwater capture and runoff, to name just a couple. In New York City, trees remove 1,100 tons of air pollution each year. But despite the social, ecological, and financial merits of urban forests, tree coverage in the U.S. is shrinking. The city of Cambridge, Massachusetts, lost on average 16 acres of urban tree canopy coverage per year between 2009 and 2018, according to a 2019 report. This was largely because of new building construction, increased paving, landscape renewal projects, and lack of adequate tree protection.
But Cambridge is not alone. Nationwide, about 175,000 acres were lost annually from 2009 to 2014, or about 1 percent of the country’s urban canopy over five years, according to the U.S. Forest Service. Now, architecture firms and government offices are working to reverse this trend. “For public health in the 21st century, we have to have cooling, and we have to have air quality, and that’s what trees do,” said Eric Kramer, principal at the Cambridge-based landscape architecture firm Reed Hilderbrand. Kramer is part of a team that leads the Cambridge Urban Forest Master Plan, a project that aims to cultivate a healthy urban forest across the city.
Reed Hilderbrand’s urban forest master plan is part of a larger effort in Cambridge to restore ecological balance in the city of 121,000 residents. Similar projects there include Stoss Landscape Urbanism’s Triangle Park, a recently completed green space in Kendall Square. Shade is Social Justice, a program funded by an Accelerating Climate Resilience grant from the Metropolitan Area Planning Council, supports the construction of shading devices all throughout Cambridge, some designed by architects Gabriel Cira and Matthew Okazaki. SHADE, a local Cambridge nonprofit led by Jeff Goldenson, enables local high schoolers to design and build shading devices in their communities.
Expanding Canopy Coverage
Similar urban forest plans have in recent years come out of cities across the U.S: In 2023, Philadelphia released the Philly Tree Plan, a road map by Hinge Collective to grow its urban canopy over the next decade. Urban forest plans are also underway in Boston, New York City, Austin, and San Francisco. Like those other programs, Reed Hilderbrand’s Cambridge Urban Forest Master Plan is not just about planting more trees—it also prioritizes retaining those that already exist. Seeds planted today won’t grow large canopies for many years, so limiting tree removal and providing solutions for the “in-between” period necessary for newly planted trees to grow tall is essential for a sustainable and healthy urban forest to take hold.
“You have to act at all scales,” said Kramer, who also teaches in the landscape programs at Harvard GSD and ETH Zurich, where he explores the future of urban forestry with students. “You have to think about the individual condition. The tree itself is living, and you have to care for that tree. It takes human intervention in most urban environments to care for a tree. But that tree is not isolated. It’s growing in a community, and that community is both ecological, cultural, and social.” Kramer and his team rely heavily on data to track progress and establish target interventions. Largely due to 20th century redlining, low-income, minority communities like in the nearby Boston neighborhood of Roxbury have less canopy coverage compared with wealthier areas. Thus, Reed Hilderbrand’s plan prioritizes areas of Cambridge with populations at greater risk of extreme heat.
Paradigm Shift
In 2023, the Biden administration allocated $1.5 billion to Urban and Community Forestry Grants as part of the Inflation Reduction Act. That same year, California received over $100 million in such grant funding, the most of any state. Today, among local officials, there is “emphasis on thinking about equitable distribution, mitigating heat, and we’re really working on ways that we can target communities in need,” said Dr. Max Robert Louis Piana, researcher, ecologist, and lecturer at Harvard GSD.
A crucial element to this work is developing deeper civic interest and engagement. Trees don’t just impact one person—even a fruit tree in someone’s front yard can provide shade for passersby. So it’s in everyone’s best interest to care for urban forests, Kramer said. That’s why community engagement is a core component of the Cambridge Urban Forest Master Plan.
“We need to have this connection to natural areas if we’re to nurture a greater global stewardship to address climate change,” Dr. Piana said. “Otherwise, it becomes distant and removed. It’s hard to wrap your head around the challenges that we face in terms of the climate crisis without experiencing biodiversity in natural areas.”
Kramer said he envisions future cities that, from ten thousand feet, will look primarily green with buildings dotting the landscape, rather than what cities are today: seas of gray with speckles of green. “I don’t think that’s impossible,” Kramer added. “Certainly, in cities we have bigger buildings and there’s going to be breaks in the forest for those buildings, but we have the capacity, both through techniques of planting and, if the investment is right, through the capacity of our city agencies and private actors to create continuous canopy in the rest of the open space. That’s what the city should look like.”
Eric Newstrom is a journalist in New York City. He writes primarily about climate change and sustainability.
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