Urban Forests

UNLIKE THEIR RURAL SIBLINGS, urban trees and the forests they fill live much more complex lives. While trees in uninhabited settings do fall prey to pests and diseases, they escape the vagaries of city life, such as soil compaction, smog, encroaching hardscape, power lines, chainsaws and perhaps the worst enemy of all: oversight.

When people forget about the benefit of urban trees and see them as inanimate objects, they are more likely to be removed. According to a 2012 published study by the U.S. Forest Service in Urban Forestry & Urban Greening, tree coverage in urban areas of the U.S. is declining at a rate of 4 million trees per year, and that is unfortunate and disturbing, says arborist and urban forester R.J. Laverne, manager of education and training for the Davey Tree Expert Company.

“Why would you put up a concrete wall to buffer highway noise when you can create a magnificent urban forest?” asks Laverne. Beyond aesthetics, urban forests offer benefits in three broad areas – environmental, economic and social, and many of the benefits are interconnected.

Urban forests benefit the environment by producing oxygen; cleaning air pollution; providing beneficial, energy-saving shade; stabilizing soil; decreasing erosion; and offering habitat and food for wildlife.

Economic benefits of trees include improved real estate value, cost savings from energy conservation and preventing the need for expensive engineered solutions to manage situations like stormwater runoff. Tools have been developed in recent years to help determine the economic value of trees, such as i-Tree, a software suite designed by the U.S. Forest Service and Davey Tree. According to the Forest Service, the average urban tree can provide as much as $2,500 in environmental services during its lifetime.

Not always straightforward are the social benefits – including physical and mental – of urban forests, which are far-reaching and often surprising.

A body of evidence has shown that exposure to urban forests including parks and green spaces has a positive effect on physical health, says Laverne, who notes that trees encourage physical activity and improve air quality, reducing respiratory and heat-related illness.

A 2010 study done by Japanese researchers regarding a popular practice known as “Shinrin-yoku,” or “forest bathing,” which involves walking through a forest for a few hours, found that those who spent time in the forest experienced lower stress, pulse and blood pressure levels. Another Japanese study done in 2007 determined that study participants who spent time in the forest experienced an increase in anti-cancer proteins.

One of the most profound studies on the subject of green spaces and trees and their effects on emotional health compared violence levels between individuals living in a Chicago public housing development. Some of the residents had access to green spaces while others did not. The study published in 2001 found that women who lived next to trees and greenery committed fewer violent and aggressive acts against their partners than those who lived surrounded by concrete. Researchers determined that people without access to green surroundings are more fatigued and aggressive and that their ability to concentrate and think through problems increased when they could see or experience greenery.

“These seminal studies were absolutely astounding,” says Laverne. “To think that a simple access view out of a window to a tree and green space could impact your emotions, ability to concentrate and social networks is incredible.”

Laverne is conducting research on the social benefits of urban forests from a different perspective. “Most of the research done up to this point has looked at the visual impact of trees and natural areas on people, but I’m instead focusing on the auditory aspects to see if the soundscape that surrounds us has an effect on how we function mentally and how it impacts our quality of life.”

Known as soundscape ecology, this area of study focuses on sound dynamics in landscapes and how sounds can serve as indicators of biodiversity and health of environments. “The classic book ‘Silent Spring’ by Rachel Carson was one of the first to suggest that the sounds in our environment may be an indicator of ecological health,” says Laverne.

In his study, Laverne takes advantage of the opportunity to study the before and after changes in sound occurring in communities like Arlington Heights, Illinois, and Minneapolis where the widespread emerald ash borer-induced death of ash trees is creating a significant change in the soundscape. Using technology developed at Cornell University, Laverne is analyzing the change in the mixture of sounds before and after tree removal, and then volunteers are listening to the recordings and taking simple concentration tests.

“The study results may provide a small piece of the puzzle regarding how we could design greener communities that are more supportive of how we function as human beings,” says Laverne.

Given the profound effects of urban forests, preserving existing forests and adding more trees is a goal of many conservationists. To offset the alarming rate of deforestation, some communities have rallied to reforest with carbon sequestration campaigns such as “Plant a Million Trees.” Adopted by cities across the country, the movement includes Chicago, Philadelphia, Los Angeles and New York, the latter of which has planted more than 900,000 trees. Other cities are working to maintain healthy urban tree populations, such as Minneapolis, which has 26 percent of its land dedicated to urban forests.

New York City urban ecologist Marielle Anzelone is currently orchestrating a large-scale art installation, “PopUp Forest,” in Times Square scheduled for the whole month of June 2016 to increase awareness of the value of green spaces. She is also working on more permanent solutions to creating greener views for New York City residents with the creation of biomes on city blocks that feature a variety of plants, including trees and wildflowers. “If installed on every block throughout the city, these biomes would provide connective habitats for birds, bees and butterflies, as well as engage people,” says Anzelone.

The biggest benefit an urban forestry program can offer people is green spaces in neighborhoods, agrees Laverne. “Whether it’s a forested playground, community garden or a pocket park with a couple of benches, the more that a community can do to provide these green spaces, the stronger the community networks will become.”

Julie Bawden-Davis is a garden writer and certified master gardener.