Before Caitlin Lenahan worked for Tree Pittsburgh — before she knew about tree biology, or advocated for tree care on a daily basis — she found it hard not to be affected by trees. She was a student in Pittsburgh at the time. She always walked the same way to get to her job at a local coffee shop. Along the way, there was one particular tree that caught her attention.
"It was huge," Lenahan said. "It was kind of the type of tree where, if you stood underneath it, in the summer all the leaves would be there, and it would be like a leafy cave that you could be inside of."
But then a huge windstorm struck, and trees were destroyed throughout the city.
Lenahan said, "I kept thinking, 'Well, the tree I like the best is still going to be there.' And it totally wasn't. It was blown apart into splinters. It was incredible. I couldn't believe it. Oh man, it was devastating. I couldn't believe it wasn't there."
Trees can have an enormous impact on life in a city, but they were never really meant to live in one. Trees aren't designed to stand alone in a park and feel the full force of the wind, to be nicked by lawnmowers, or to have the soil over their roots compacted by sidewalks and roads.
But in a city, trees are exposed to these things every day, and sometimes they need a bit of human intervention to survive. And this is where the Tree Tenders come in.
It's a chilly evening, one of the first to really feel like fall, when the Troy Hill Tree Tenders hit the streets in Pittsburgh's North Side.
"What we just did was, pull all the weeds in the pit, fluff up the mulch a little bit, kind of fluff up the feathers, and then we put a thin layer of new mulch down," said Kathy Croft, one of about 10 volunteers to pitch in. They each wear a bright yellow vest with the words "TREE TENDER" in capital letters on the back.
"We feel it's our job to make this neighborhood look better, and the fastest way is to populate the neighborhood with trees," she said.
Tree Tenders was developed by Tree Pittsburgh. It teaches volunteers, like Croft, to care for newly planted trees in their own communities. First, they learn about urban forestry and tree identification. Then they put these lessons to work.
Jake Milofsky coordinates the Troy Hill workshop.
"Up here at the top of Rialto Street, there are eleven new trees that have been planted — red buds and serviceberries," Milofsky said. "Having that new layer of mulch down will be beneficial as it gets cold and salt trucks come by."
Since they started keeping track, the survival rate for new trees planted by volunteers in Pittsburgh is 97 percent. This is an unprecedented number among cities with similar programs. It's even higher than the survival rate of trees planted by contractors. Lenahan says that this is most likely because the volunteers are more invested. They're around day to day.
"In the past 15 years, we could look at data about when new trees were planted in the city and they were dying within 5 to 7 years, and presumably, that was because nobody was looking after them," Lenahan said. "They were put in the ground and not maintained: no water, the stakes weren't pulled, and they were forgotten about. Tree Tenders are really eyes on the street."
And this is important, because while Pittsburgh does have a forestry budget, most of it goes toward maintaining trees, and none of it goes toward planting new ones.
This doesn't mean that new trees aren't planted. It just means that it's up to nonprofits, like Tree Pittsburgh, to help do the work that the city can't afford to do on its own. So, when new trees are planted, it's that much more important to make sure that they survive.
And when they do, trees can lead to some profound benefits.
Trees are known to cool houses and save homeowners on electric bills in the summer. In the winter, they serve as windbreaks and reduce heat loss. Research conducted in 2008 by Tree Pittsburgh and the Davey Resource Group estimates these savings alone at $1.2 million annually.
In Troy Hill, Kathy Croft says she can feel the difference.
"I have a thermometer in my back yard," Croft said, "and this summer several times I knew what the temperature was in the sun — it was in the 90s — and I would go to the backyard and check the thermometer there, and it would be 10 to 12 degrees cooler in my backyard because of the cover of the foliage. And that's pretty nice."
More than that, trees result in cleaner air and less erosion and storm runoff. They can significantly increase property values. Some studies have shown that trees can even reduce crime rates and yield greater sales in business districts.
All things considered, Tree Pittsburgh calculates that every dollar invested in street trees yields almost $3 in benefits. In Pittsburgh, that translates to $2.4 million every year.
And if the trees keep growing, that number will get bigger, too.