Seattle's new zoning rules dial up tension around preserving tree canopy

Seattle is currently mapping how it will grow over the next 20 years. Mayor Bruce Harrell wants to double the city’s housing capacity, with the hope of bringing down costs. But as residential neighborhoods open up to new types of housing, the city’s environmental impact statement predicts “moderate tree canopy loss” as a result.

Tree advocates say the city can achieve its density goals while retaining existing trees for their climate and health benefits. But developers oppose those rules and city officials say rather than restrict new development, they hope to plant more trees on public land and rights of way.

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Next month, city officials will forward the first piece of legislation to the City Council to implement the zoning update. It will focus on allowing duplexes, fourplexes, and other new types of housing in neighborhood residential zones, in accordance with a new state law. Then in May, the city will forward the second piece of legislation focused on denser buildings in neighborhood centers.

Tree advocates say these changes are coming on top of the city's recent ordinance that gives developers greater ability to remove even so-called “exceptional” trees, those 24 inches across or greater.

Craig Bachmann is a master arborist based in Seattle who has consulted on development projects.

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“It’s my experience that most developers would prefer to have a blank slate rectangle to do what they want," he said. "I’m not trying to throw stones; I think it’s just the reality.”

Bachmann said Seattle's tree ordinance contains a formula that tends to favor tree removal in development projects, rather than building closer to trees as the city of Portland does. He hopes the city will prioritize existing trees even as it ramps up more housing.

“When possible, let’s keep the trees we have,” Bachmann said. “Because they’ll never be as big in our lifetime if we take them down and try to replace them.”

Late last year, Seattle resident Carlen Luke heard the hum of machinery outside her Lake City home.

“On December 20th I heard the saws and the chipper and that’s when I came out and saw tree service provider cutting those branches off,” Luke said.

The tree was a 35-inch diameter Douglas Fir on a property under development -- there was no permit posted for its removal. Luke complained, and the workers gave up for the time being. But Luke said once they obtained the required permit, city rules provided no grounds to save the tree.

Groups like Tree Action Seattle want the city’s big trees to remain, even as they’re surrounded by more density. They say the benefits of trees for cooling, stormwater retention, and public health will be even more important as more residents make their homes around them, especially in neighborhoods like Luke’s with lower tree canopy, which is linked to hotter temperatures and worse health outcomes.

City officials say they’ve sought a lot of community feedback to inform their approach, and they’re trying to balance a lot of competing goals.

Brennon Staley is a strategic advisor with Seattle’s Office of Planning and Community Development.

He said property owners in lower-canopy areas told the city they don’t want to be singled out for environmental restrictions like being required to retain trees.

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“They want to have the same rights and abilities to develop as people in other areas,” Staley said. He said the city can compensate by planting trees on public land and rights of way.

“That’s how we think we can make a difference in trying to bring up the canopy in those areas,” Staley said.

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Lauren Urgenson manages the city’s urban forestry programs at the Office of Sustainability and Environment. She said the city has numerous initiatives including Seattle Public Utilities’ tree giveaway program Trees for Neighborhoods to bring more shade and cooling to low-canopy neighborhoods, which are often associated with disadvantages related to poor health and poverty, based on the city’s census data.

“All of this work has a focus and a prioritization of those neighborhoods that have low canopy,” she said, “and those neighborhoods that are experiencing disproportionate impact from extreme heat.”

A 2021 study in King County found that areas with more pavement and fewer trees got much hotter during heat waves and experienced less cooling overnight. Tree advocates want the city to require unpaved space for trees on lots where developers build new “middle” housing like duplexes and fourplexes. But Staley said the mayor’s plan allows outdoor spaces to be paved, if that’s what residents want.

“This is really important to people – to have some green space that they can call their own, they can plant it or use it as patio, barbecue, etcetera,” Staley said.

Parker Dawson is the Seattle government affairs manager for the Master Builders Association of King and Snohomish counties. He said homebuilders are largely supportive of Harrell’s proposed update to guide new housing growth.

“It’s certainly a great first step in achieving a lot of the housing goals that Seattle as a whole is looking for,” he said.

These changes could take Seattle farther from its existing goal for 30% tree canopy citywide – the last assessment said the city is slowly losing ground on that goal.

Urban forestry manager Lauren Urgenson said that assessment indicated that development was associated with tree loss.

“Although that wasn’t the primary reason for canopy loss citywide, on sites where there is development there was a higher percentage of canopy lost,” she said.

But Dawson with the Master Builders Association said tree canopy will be replenished as newly planted trees get bigger.

“When it comes to construction, builders are planting and protecting more than four times the number of trees they’re removing,” he said.

That’s the crux of this debate. Builders prefer to plant new trees once a project is completed, while tree advocates want the city to preserve existing trees.

Joshua Morris, who chairs the city’s Urban Forestry Commission, said it’s not realistic to put all the city’s tree canopy on public land and rights of way where trees have to compete with utility lines and other infrastructure.

“It is so much harder to plant and grow and maintain and find space for these new trees,” he said. “Maintaining trees where they’re currently standing is so important.”

Morris said in low-canopy neighborhoods, preventing tree removal is even more vital.

In Lake City, Carlen Luke was not able to save the big Douglas Fir nearby. After more than a month of protests, the developer cut it down.

Luke said the tree was close to the lot line so it could have been spared while adding the same amount of housing.

The developer, Legacy Group Capital, declined to comment. Other developers said it is simply too expensive to alter an existing project once it’s underway.