Thinking 50 years ahead: Phil Bennett on Climate Change and Urban Forestry

Photo Credit: Arnaud Mesureur

$158-195 million. That’s the price tag the City of Snoqualmie recently put on the value its public forests will provide to the city over the next 50 years. That just counts their benefits for stormwater retention, carbon sequestration and water quality. When it comes to the value of trees in an urban setting, those are only the tip of the iceberg. Studies have shown that urban trees can also reduce the use of air conditioning by as much as 30% and lower the temperature by as much as 14 degrees Fahrenheit on hot days. Trees are even good for our mental health; we’re less prone to anxiety, depression and even violence when we’re around more green spaces.

“There’s a lot with people’s sense of well-being that’s tied to being able to be amongst, and see trees.”

  That’s Phil Bennett, the Urban Forester for the City of Snoqualmie. Bennett started working with trees in 2007 and became an arborist. After getting laid off in the recession, an opportunity came up for a job in Snoqualmie. He started out working in parks maintenance, but “from there,” he recounted, “I basically built a[n urban forestry] program. I wrote my [own] job description.” That job is to manage and tend to the green spaces around the city, be it forest land, trees on private property, street trees or trees in parks. That goes beyond just being an arborist, he explained. “I think most urban foresters are arborists first … You start at the biological understanding of trees at an individual level, and then move to a system-level understanding. So urban forestry is really about a system-level understanding of natural resources in cities.”

The trouble is, those natural resources, Snoqualmie’s valuable forests, are threatened.

“What we know is that the native ranges of western red cedar, western hemlock and Douglas firs are moving north,” says Bennett. These trees, accustomed to Western Washington’s historically wet climate, make up the majority of our forests, but whether they will continue to do so is a different story. “What we suspect at least, is the genetics of the trees that are currently in Snoqualmie are not going to be viable in the climate scenarios over even the next 50 years.”

 According to Bennett, that’s for two main reasons. First, increased temperatures are increasing the length of time for which fungi can be active in the soils. Fungal decays, he says, are having a “field day” in our forests. Second, the “hydroperiod,” the length of time between rainfalls, particularly in summer, is increasing, now commonly lasting three or four months on end and causing trees to die of drought. “We’re already seeing in Snoqualmie, a large amount of mortality in western hemlock and western red cedar in all age groups.” In other words, our trees are dying.

That’s not to say they’re doomed, however; we’re far from it. Bennett, and others like him, are working hard to preserve the evergreen of the evergreen state. While the genetics of the trees here may not be adapted to a drier, hotter climate, western red cedars can still be found in Northern California. The genetics of the trees there are different from those that grow here, making them better adapted to the effects that climate change will have on our region. “One thing we’re starting to do is to try and find seed sources in the southern end of the range of our native trees, so that we can bring seed starts from there and grow those trees here, in anticipation that they’ll be better adapted to the upcoming [climate] conditions,” explains Bennett. He’s also helping to shift the makeup of the forests by planting species like grand fir and shore pine, which are much more tolerant of long droughts. As they plant, they’re mulching heavily with wood chips and bringing in logs to decompose, which not only fertilizes the forest but also holds and retains moisture during dry spells.

While climate change may be making his job more difficult, it also makes it all the more important. “Urban forestry,” Bennett says, “has not yet had its day … In the next couple of decades, it is going to become more and more important.” After all, trees help protect cities from flooding, prevent or mitigate heat islands, reduce energy consumption from air conditioning, clean up air pollution and sequester greenhouse gasses into the ground. They can be a one-stop-shop for combating the negative effects of climate change.

Bennett isn’t alone in his endeavors; he helped found the Green Snoqualmie Partnership, a group of citizen volunteers who help to maintain the city’s parks and natural areas by removing aggressive weeds, mulching, watering and planting trees. “It also serves as an advocacy piece for urban forestry,” Bennett says. “It’s an education and advocacy program in a sense because it lets people know what we’re doing, why it’s important and how they can help.”

The partnership, founded in 2016, is part of a larger group of 15 Green City Partnerships across Western Washington, all partnered with the nonprofit organization Forterra. They’re always looking for volunteers, so you can find more information about them and the work they’re doing to keep our cities green here. 

For Bennett’s part, he’ll keep doing what he does best: tending trees with an eye to the future. After all, when you plant something that can last a lifetime, it serves well to be thinking a few decades ahead.