In cities across Pennsylvania, street trees can help cool ever-hotter temperatures. But they present their own problems

One in three days this summer has reached 90 degrees in central Pennsylvania, a sign of more intense heat linked to climate change.

In cities, sidewalks and roads trap heat and can make afternoons even hotter – the so-called urban heat island effect. Cities like Harrisburg, Lancaster and York are planting trees to try to control rising temperatures.

But there may be obstacles to this solution.

On a recent Tuesday along Market Street in downtown Harrisburg, a few blocks east of the Susquehanna River, everyone had to be somewhere.

Sunbeams chased walkers down sidewalks, down brush-filled alleyways, and the world became a jumble of white concrete and roadside bodegas.

“A lot of these houses, they don’t have, like, roof fronts, so they don’t have a lot of shade,” Gary Lewis said. “Trees help that a bit. In the summer, anyway.

Gary Lewis walks down Market Street in Harrisburg on August 2, 2022. He is looking for shady places to walk on his way to work.

Lewis has lived in Harrisburg for nearly five years and walks to work every day.

As much as he can, he stays in the shade, like others in Market on a day when the temperature was heading towards 91.

The Harrisburg Forest Department recently planted 86 street trees in three neighborhoods as part of a grant-funded project. According to the Arbor Day Foundation, in one year a mature tree will absorb about 48 pounds of carbon dioxide from the atmosphere.

Thus, the new Harrisburg trees will consume more than 4,000 pounds of CO2 when they reach maturity. That sounds like a lot at first, but to put it into context, that consumption would wipe out less than seven-ten-millionths of a percent of Pennsylvania’s total emissions.

But trees do more than absorb carbon dioxide. The Pennsylvania Department of Conservation and Natural Resources says community trees filter stormwater, cool on hot days in the shade, and prevent flooding. And, a large tree can provide a day’s supply of oxygen for up to four people.

The US Forest Service has even found that as forest cover increases, crime can decrease.

Tisha Barber and her students pick up trash along Market Street as part of the Harrisburg Housing Authority’s Environmental Teen Corporation. They would like to have more trees added to the area.

“You can’t go wrong planting trees! Barber said.

Economically, trees increase property value by up to 15% and can save people 3% on their energy bills, according to the Arbor Day Foundation.

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Tisha Barber, center, and her students from the Environmental Teen Corporation of the Harrisburg Housing Authority pick up trash along Market Street in Harrisburg on August 2, 2022.

But there are still downsides to planting trees along city streets.

On the one hand, there is the cost.

The City of Lancaster says planting a street tree can cost between $165 and $230 (including labor costs).

Homeowners can apply for grants from the city, but funds are limited. People over 65 and low-income families can also apply for financial assistance.

And if a tree’s roots bend a sidewalk or interfere with sewer lines, the homeowner will have to pay to have it removed and repair any damage.

It can cost thousands of dollars.

And many cities, including Harrisburg and Lancaster, require homeowners to have a permit to remove or plant street trees. They also limit the size and type of tree planted. City officials say the potential expense may make people reluctant to plant trees.

Some people have started to shave concrete or install concrete shims as short-term solutions available at lower cost.

When tree roots are weak, according to the Bartlett Tree Research Laboratory, contractors can try to bridge sidewalks. Sonotubes – boxes of peelable Pillsbury cinnamon rolls used to shape concrete – create columns along the sidewalk to support the walkway and allow roots to grow.

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A sidewalk damaged by tree roots and repaired along North 16th Street in Harrisburg on August 2, 2022.

Some people even forgo planting trees because it’s too expensive and disruptive.

Kathy Ford lives about a mile from where Lewis commutes to work, near Primrose and North 17th streets. The city funded the planting of street trees in her neighborhood, just two blocks from where she had to cut down her own trees because of the damage they had done to her sidewalk.

It cost $3,000, she said.

“Then I had to redo my concrete from start to finish, because it cracked everything. You see that of the lady [sidewalk] just there? I can’t afford to have it repaired. »

Ford gestures toward the asphalt his neighbor has poured between two uneven concrete slabs, creating a makeshift ramp.

“They shouldn’t have planted trees there. You know why? Because we had to take ours. See what it does to the sidewalk after years? »

“If someone trips on your sidewalk, what insurance? You are responsible,” Ford said with a laugh.

But for some people, these trees are their life.

Cody Kiefer stands in the middle of a neighborhood of houses with wide windows, red brick, white moldings and Doric columns.

Lancaster City appointed Kiefer its Urban Forester in September 2021, and since then he has worked closely with engineers to put together individualized sidewalk projects to meet the needs of the city and homeowners.

He points to the pink, white and orange paint sprays that tattoo the concrete slabs, some pushed back by tree roots and others simply poorly maintained. The city cited these areas for sidewalk diversion and replacement, gas line repair, and water line repair.

He says they have to consider much more than the landlord when uprooting and planting new trees along the street.

“In reality, we have varying rights of way on the streets,” Kiefer said.

“And so, if we really want to put street trees, we have to stop planting them in a two-foot or three-foot wide strip like this. We need to push the sidewalks as far into the right-of-way as possible to provide maximum space here.

“The best solution to this problem is to give the tree more room.”

Diverting sidewalks is usually the best choice for homes that have a bit more space to spare between the street and the home’s “right-of-way,” he said.

It also allows a ton of extra water to seep into the ground instead of flowing down the streets, escaping through sewer tunnels and ending up in drinking water.

“We’re talking about maybe 30-40% of a rainfall event – a typical, average rainfall event – can be absorbed in the area directly under a tree canopy…It’s gallons and gallons – at the level of the trees – from precipitation that doesn’t reach the terrain. It just evaporates into the atmosphere. So aggregating this at the city scale is not trivial.

But townhouses in many neighborhoods can’t afford to lose the extra space. Most don’t even have that extra space to begin with. For these homes, Kiefer recommends smaller planters with flowers and ferns to refresh the city’s cityscape.

Part of the reason why real forests reduce heat island effects, Kiefer said, is the combination of large trees and small plants and brush.

“That’s what Philadelphia has done in some of their low-income neighborhoods… By growing certain plants through planters in those neighborhoods, what they’ve seen is that people have really started to s ‘own it and saw the potential in their community and their streets,’ he said. said.

Kiefer said studies have linked urban forests to factors such as reduced hospitalization rates, increased recovery times, reduced cases of childhood asthma and equity in school performance.

Drea Mitchell understands where Kiefer is coming from.

Back on Market Street, Mitchell sits and admires her slice of Harrisburg. The hardwood in front of his house is so big that it also shades his neighbor’s house.

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Drea Mitch, Michael Hill and King Hill, 4, sit on their porch under the shade of trees in the 1500 block of Market Street in Harrisburg on August 2, 2022.

“Oh yeah, my shadow, I love it,” she said.

“You get a plus one and a minus, too. So you get the shadow, but you get the little critters that come with it. But I can’t complain; I’ll take the creatures.

Across the road there is land converted to a prayer garden with grass, flowers and bushes, a few feet behind the new street trees.

“I saw people going down there,” she said, smiling.

“They sit and, you know, it’s like a garden of paradise.”

So the midday sun was beating down. Except, on this strip of Market Street, not on cement, but on plants and dirt.

This story is produced in partnership with StateImpact Pennsylvania, a collaboration between WESA, The Allegheny Front, WITF and WHYY.



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