It's only 78 degrees in Portland on this summer afternoon, but on the sidewalk, it's hot enough to melt a box of crayons. But under the cover of a massive maple tree on the city's Eastern Prom, in the shade, with the sudden breeze, it instantly feels a few degrees cooler.
And it might be. That's because of something called the urban heat island effect.
"Lots of heat washes off all that pavement," says Portland City Arborist Mark Reiland.
The pavement and buildings in a city absorb the sun's heat and then re-emit it. Urban neighborhoods without trees to shade the sun can be up to 10 degrees hotter than neighborhoods with lots of trees.
And that's not all they do for us.
"Trees are passively filtering the air around us, taking in all the pollutants," Reiland says. "Like from that wonderfully tuned engine that just went by."
The benefits go on: filtering rainwater, lowering air conditioning costs and even boosting sales for shops near trees.
But despite the best efforts of Reiland and the Parks department, Portland is slowly losing its tree canopy.
Portland Parks Department Director Ethan Hipple says the city plants about 200 new trees every year.
"But if we had a significant drought or significant presence of a new pest like emerald ash borer or hemlock wooly adelgid or other pests, we might lose, you know, 250 or even 300 trees in a year," he says.
That's been putting the city at a yearly deficit of 80-100 trees on average.
Portland's urban forest is facing myriad challenges, Hipple says: changing temperatures due to climate change, drought, pests, storm damage, nutrient-deficient soil, development, invasive species and more.
"So we asked for help from the Portland Parks Conservancy, and they agreed immediately to help fund a urban forest master plan," Hipple says.
And one major goal of the plan is to bolster public awareness and participation. Portland has some 20,000 street trees that Reiland and his team manage. But as much as 70% of the urban forest is on private property. That means, for the plan to work, the city needs buy-in from property owners, universities and businesses.
"This isn't about forcing anyone to do anything. It's about making people aware of why this is important and the role that they can play," says
Rachel Comte, a master arborist and co-founder of Urban Canopy Works.
Her organization has helped cities across the country come up with master forestry plans. She says she's trying to get urban planners to understand how important trees really are for day-to-day life and for climate resilience.
Many cities "are still thinking about trees as an aesthetic thing," she says. "But it really needs to be considered infrastructure."
Comte has been working with city officials on the Portland plan, which will be finalized by next spring.
In the meantime, Reiland will be working the urban forest. And there's a lot to do.
"For fall planting, this whole esplanade. See a couple stumps? We had a bunch of ash trees here, which — ash tree right under the power lines? — But Emerald Ash Borer took care of that for us," he jokes. "Just want to replant with something a little more appropriate [for the area]."
There are many projects the small team of six is constantly juggling. And Reiland is hoping the Portland community will soon play a more active role in stewarding the forest.
"It would be fantastic to kind get everybody on the same page about why we do what we do, why it's important," he says.
The city will hold a public workshop on its urban forest plan on Sept. 17 at Merrill Auditorium Rehearsal Hall.
