Reaping the benefits of city trees

Life is hard for a tree that grows in Brooklyn. It struggles with bad soil, pollution, heat, drought, flooding, snowstorms, and road salt, plus sidewalks and pedestrians compacting the ground around its roots all day long.

But trees in Brooklyn and other cities have an advocate in Nina Bassuk, professor in the Horticulture Section of Cornell University’s School of Integrative Plant Science. Raised in that same New York City borough, Bassuk has dedicated her career to helping trees survive and thrive in harsh urban settings as the founder and director of the Urban Horticulture Institute (UHI).

"Trees are a way to make a big environmental impact in cities," said Bassuk. "My work finds ways to grow them and keep them healthy so they can provide services to people and the environment."

Top left: Bassuk’s students planted a run-off filtering bioswale along Tower Road on the Cornell campus. Top right: For Arbor Day, they hang tree tags on the Ag Quad enumerating the ecosystem benefits. Above: Bassuk tests soil compaction on the National Mall, where she studied how to improve the health of trees there.

Today, urban trees are getting the long-overdue respect they deserve. 

“Beauty is a value,” Bassuk said. But she also knows that dollars talk. For 25 years she’s worked with students on Cornell’s Ithaca campus and others in urban areas to calculate the economic benefits of the ecosystem services trees provide.

One calculation indicates that every dollar spent on a tree in New York City returns three to five dollars in ecosystem services, particularly when it comes to mitigating climate change. Tree-lined streets and parks help reduce stormwater runoff, control erosion, improve air quality, and provide habitat for birds and pollinating insects. Leaf canopies reduce hotter temperatures experienced in cities by as much as much as 20 degrees. Lower temperatures mean less energy use from air conditioners. And trees sequester carbon from the atmosphere.

“The importance of trees is much greater than people realize,” Bassuk said. “I hate the idea that people think trees are just nice. There’s so much more that they offer.”

‘Tree equity’ needed

But trees and their benefits have not been distributed equally across urban neighborhoods, she added. Redlining – the discriminatory practice of withholding services from mortgages to healthcare in underserved communities – has limited tree planting in those communities, impacting them in ways far beyond aesthetics.

“Street and park trees could be the most democratic effectors of climate change mitigation, but they are not equitably distributed. Lower income neighborhoods have poor green infrastructure compared to wealthier areas,” Bassuk said. “This creates serious neighborhood cooling problems and affects the health of thousands of people, especially as summers get hotter due to climate change. Trees affect people’s lives.”

Tree equity – efforts to bring green canopies into low-income neighborhoods – is having a watershed moment, and Bassuk is hopeful that more people will understand the importance of such equity for both human and environmental preservation. The subject has President Biden’s attention. His proposed infrastructure bill allocates $3 billion for tree planting in underserved communities.

Above: Bassuk (center) and her ‘Urban Eden’ class plant trees and shrubs in the shadow of Bailey Hall on the Cornell campus. Every spring, students in the class complete a woody plant landscape makeover on campus from design through installation.

Integrated strategies

No matter the political climate, a tree, like the one tree growing in Brooklyn, often has a difficult and short life. To address this, Bassuk has a multifaceted approach to be sure we reap the benefits of urban trees:

• She developed of a line of hybrid oaks tough enough to withstand urban conditions, as well as techniques for propagating them.
• As poor soil limits a tree’s viability, she created a specialized growing medium – CU-Structural Soil® – that allows tree roots to expand and find water without heaving sidewalks.
• Her Woody Plants Database advances the art and science of selecting the right tree and shrub for the location, delivering site specific recommendations.
• UHI outreach activities connect her research initiatives with urban planners, landscape architects and property owners.

Bassuk will be retiring soon, and while the impact of her work will surely continue, the UHI’s future is unclear. She’s hopeful that her findings will continue to be applied as urban populations grow and climate change issues become more critical. 

“We felt climate change in urban areas before the term became a household word,” Bassuk said. “Urban areas are much more influenced by climate change than rural areas. People must recognize this is an important issue.”