by William Hengst
Trees have historically been revered for their ability to provide beauty and shade, which results in cooler temperatures and reduces air pollution. Trees today also are considered nature’s best weapon in the fight against climate change because of their ability to extract carbon dioxide (CO2) from the atmosphere and store much of it in the woody tissues of their trunks, branches and roots. Trees then convert the CO2 into sugars, cellulose and other carbon-containing carbohydrates for food and growth.
All trees store carbon at different rates and amounts, depending on their size, life span and growth rate. The longer the life span, the greater the carbon benefit. In other words, older trees play a vital role in nature’s fight against climate change. Planting more trees also will contribute to this battle as these trees mature.
The best way to identify the degree to which urban forests play a role in reducing greenhouse gas emissions is through mapping the tree-canopy cover – the layer of leaves, branches and stems that cover the ground when viewed from above by aerial satellite imagery. This is something that scientists at the U.S. Forest Service study.
One study found that the nation’s overall tree coverage averaged around 40%, while Philadelphia’s overall tree cover was only 20%. (Tree cover in Baltimore, New York City and Washington, D.C. was higher than Philadelphia.) Older neighborhoods in Philadelphia, such as Frankford, Fishtown and others close to the Delaware River, tend to have very low tree cover.
The study estimated that the Philadelphia urban forest contains 2.9 million trees. It also found that the nation’s coverage of impervious surfaces (asphalt or concrete hard surfaces, but excluding roads) are increasing, as are Philadelphia’s impervious surfaces, mostly due to development. These surfaces create a health problem on hot summer days when temperatures become extreme; this called the “heat island effect.”
Tree planting in Philadelphia has a long history dating back to the 17th century when, to paraphrase from an article about Philadelphia’s trees by historian Laura Turner Igoe, William Penn and his surveyor laid out Philadelphia’s streets and envisioned trees and green space as important components for this early Greene Country Towne. They even named the east-west streets after local tree varieties.
In the mid-19th century, the Fairmount Park Commission was established with responsibility for maintaining over two million public trees in all city parks, as well as overseeing the upkeep of over 300,000 existing street trees. A Street Tree Division was created in 1912, and part of its job was to plant street trees in front of private homes. Many of those trees were planted in Center City. The Tree Division also was responsible for removing dead or diseased street trees.
Today, the Pennsylvania Horticultural Society and Philadelphia Parks & Recreation, which replaced the Park Commission in 2010, continue with tree-care and tree-planting programs throughout the city with the help of neighborhood volunteer groups.
PHS started planting street trees in 1993 through its Tree Tenders program, which trains volunteers who must complete a nine-hour, hands-on class in order to be certified. The course covers tree biology and identification, tree-planting techniques, tree pruning and maintenance, as well as organizing community groups.
Today, 32 Tree Tenders groups are active in Philadelphia’s neighborhoods, planting mostly street trees along city sidewalks and occasionally yard trees on school and church properties. To date, they have planted 15,000 trees throughout the city.
Tree Tenders also plant trees in Bucks, Chester, Delaware and Montgomery Counties.
“We plant as many as 60 different tree species in the spring and fall each year, and look for the right tree for the right spot that is hardy enough to survive,” said Tree Tenders manager Mindy Maslin. “Their survival rate is over 90%.”
Currently, trees and concrete cuts on sidewalks are free and available in neighborhoods with an active Tree Tenders group. Online applications for Spring 2020 planting can be found on PHS’ website, or at the PHS Urban Forest Cloud.
Another study by the Forest Service found that residential neighborhoods in Philadelphia account for the majority of the city’s tree canopy, and also have the most land still available for planting more trees. The urban tree canopy is a vital city asset that reduces stormwater runoff, improves air quality and lowers the city’s carbon footprint. The study also found that tree cover in Philadelphia’s poorer neighborhoods is far less than tree cover in wealthier neighborhoods.
Parks & Recreation’s Tree Philly program plants around 900 street trees each year. Recently, it switched priorities toward planting more street trees and yard trees in poorer neighborhoods with too few trees. Tree Philly has also set an ambitious goal of reaching a 30% tree canopy in all city neighborhoods.
According to Tree Philly program manager Erica Smith Fichman, “We run a yard tree giveaway program, which hosts events with community groups to educate people on how to plant and care for trees, and distributes free trees for them to take home and plant in their yards. We have distributed over 23,000 yard trees to Philadelphia residents since 2012. This fall, we are partnering with over 23 community organizations all over the city by giving away more yard trees in neighborhoods like Kensington, University City and South and Northeast Philadelphia, which are most in need of trees.”
An upcoming tree giveaway event in Northwest Philadelphia will be held on Saturday, Nov. 2 at the East Falls Farmer’s Market, 4100 Ridge Ave. from 10 a.m. to 2 p.m. Registration is already full, but walk-ins may be able to receive a tree. Call 267-307-4239 for further information.
“If we are going to reach our goal of 30% tree cover, we need to engage with more residents and support them in planting and caring for trees in their own yards,” Fichman said. “Trees cool our city and are crucial to air and water quality. These things are intricately related to climate change, and trees are one of the main tools we have to creating a more resilient city. The urban forest is a complex system, and it includes all of our trees on public and private land in the city. Giving away yard trees is a crucial way to meet Philadelphia’s tree canopy goals, but street trees are also an important piece of the puzzle.”
Maslin added, “PHS has developed a map to use as a tool for Tree Tenders groups to identify the highest priority planting areas in their neighborhoods based on low tree cover. We are also working with neighborhoods that are identified as environmental justice priorities, because they not only have low tree cover but also high population density, high crime and low incomes.
“We have targeted these neighborhoods for more extensive tree planting. In the next year, we will be working with partners in Hunting Park and North Philadelphia to offer bilingual Tree Tenders classes and provide materials in Spanish to increase interest in tree planting.”
You can contact William Hengst at firstname.lastname@example.org with any comments, suggestions or questions.