Philadelphia could be a lot greener. Only 20 percent of the city’s ground is covered by trees, which is below the national average (27 percent) — a little lower than New York (21 percent), Detroit (23 percent) and Baltimore (27 percent), and a lot lower than Washington D.C. (36 percent) or Pittsburgh (42 percent). But according to a 2011 study, the city has the potential for a total tree canopy of nearly 70 percent.
To increase the percentage of trees in each neighborhood to 30 percent by 2025 — a goal set by Mayor Michael Nutter in 2008 — the city has implemented multiple initiatives to plant more trees. Philadelphia Parks and Recreation’s TreePhilly program gives residents free trees to plant in their yards or sidewalks, the Pennsylvania Horticultural Society’s TreeVitalize organizes tree planting events, and the Philadelphia Water Department plant trees through its green stormwater infrastructure program, Green City, Clean Waters.
But according to TreePhilly’s program manager Erica Smith, that’s not enough.
“Lack of funding absolutely limits the number of trees that we can plant city wide,” Smith said.
That’s going to get a little better with $250,000 watershed protection grant that Philadelphia got from Pennsylvania’s Department of Environmental Protection. The Growing Greener program, which receives funding from landfill tipping fees, gave over $20 million to 106 projects to clean up local waters statewide.
“It’s a significant amount for us,” said Frances Piller, operations manager with Philadelphia Parks and Recreation.
Piller said the city’s fund for planting trees has fluctuated over the last few years. Fiscal year 2017 was a good one, she said, with a $400,000 allocation that allowed the city to place 548 trees this fall. The average has been $300,000 per year.
“So, this does help with our backlog of requests that we have,” Piller said. “It will allow us to plant at least 400 trees extra in the next three years, in specific areas that have requested trees.”
Still, Piller said the demand for trees is bigger than the city’s capacity to pay for them. The price for trees depends on where they’re planted, since each district — Northeast, Northwest, Center City, South Philly and Cobbs Creek — has a different vendor with its own price structure.
Many people love trees. They improve air and water quality, they provided shade in the summer and a break from cold winter winds, they make a neighborhood more appealing, which could increase property value and decrease crime, and they even reduce stress. But not everyone wants them on their property.
In fact, a street tree survey done in South Philadelphia by the Delaware Valley Regional Planning Commission in 2013 found that neighbors were about equally divided between people wanting to have more trees and those wanting to get rid of the trees on their streets.
“Sometimes it’s a simple as they don’t want to clean after the tree,” TreePhilly’s Smith said. “Trees are living things and they drop leaves in the fall, maybe there are birds sitting on the tree pooping on their cars — I hear that one a lot — and you can’t always control how big it will grow.”
Although today the city takes a lot of things into consideration when picking what tree to plant in a specific location — reliability, disease resistance, amount of fruit, over head wires, the size of the sidewalk, accessibility issues and underground utilities — Smith said that was not always the case.
The project funded with PA’s Growing Greener grant — managed through the Department of Parks and Recreation with grant administration help from the Philadelphia City Planning Commission — also intends to narrow trees bad reputation among some residents by reinforcing their positive impact and environmental importance. This has been especially the case in tree desert areas like Chinatown, North Philadelphia, the Riverwards and South Philadelphia. PhillyTreeMap, a web-based map database of trees in the greater Philadelphia region, shows where there’s more of a need.
Philadelphia’s proposal was based on the need of improving water quality and remediating erosion in the Delaware Estuary Watershed. According to a report of Philadelphia’s tree canopy, the Delaware River subwatershed — the portion of the city that drains directly to the Delaware, also known as Delaware Direct — has the lowest percentage of its land area covered by tree canopy, at 7 percent.
“Trees can benefit water quality in urban settings mainly by reducing stormwater runoff,” said Matthew Fritch, Philadelphia Water Department’s expert on watershed sciences. “Tree canopy intercepts rainfall, and the roots and soil underneath help capture and infiltrate water to keep it out of our sewer system.”
Stormwater is all the water that is not absorbed by the ground after it rains or snows, and it flows over rooftops, sidewalks and streets into rivers and creeks, carrying everything it finds on its way — dirt, dog poop, oil from cars and other pollutants. This is called nonpoint source pollution.
“A lot of what the tree does is it captures the water and then funnels it down the trunk, so it can run down the trunk of the tree and then absorb more slowly in the soil at the base of the tree,” Smith said. “The rain will then drip off of the leaves at a much slower pace than if the rain was hitting the ground directly.”
The slower the water hits the ground, the bigger the capacity of the ground to soak it up. When the rain hits the ground with more force, the soil absorption capacity diminishes and more water — and sediments — run off the top, causing erosion.
“The erosion is due to the volume and intensity of the stormwater entering the stream during a storm — this can be from any stormwater outfall, not just a combined sewer outfall,” said Fritch on an email. “The stream can rise very quickly, and the force of the water destabilizes the streambanks. Erosion is also coupled with sedimentation, where fine sediment is washed into the stream and creates a poor environment for fish and aquatic life.”
Runoffs also carry nutrients from animal excrements or excess fertilizer in resident’s gardens, which increases the river algae population and diminished the dissolved oxygen in the water.
The new trees will be planted in the Wissahickon creek watershed and in areas where the city discharge excess wastewater into the river to prevent flooding when the combined sewer system reaches its full capacity. There are 165 combined sewer outfalls in Philadelphia with 40 to 80 discharges a year. By planting trees in these areas, the project supports Philadelphia Water Department’s efforts to comply with EPA’s Combined Sewer Overflow regulation.
“Those areas are directly impacting the river, which is the point of the grant — to increase water quality — and there’s a lot of need in a lot of areas; these gives us the flexibility to plant them where they’re most needed,” Smith said.
The exact location of the new trees will be determined in the next months. The trees should be planted by 2020.
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