After more than a decade, Seattle passes new rules to protect more city trees

Seattle is known as the Emerald City, but over the past couple decades it’s been losing a lot of what makes it green. The city’s most recent tree canopy assessment, released in 2021, found that Seattle’s tree cover had dropped to 28.1% — short of a goal set nearly 15 years earlier of getting canopy coverage to at least 30%.

To protect more trees from development, many urban forest advocates have spent years asking for an update to rules for removing and replacing trees in Seattle. This week, those rules were finally updated.

In a 6-1 vote, the Seattle City Council approved a sweeping update Tuesday to the tree ordinance that will change the way the city balances growth with tree canopy cover. The city's current policy was an interim ordinance enacted in 2009.

"Broadly, the new ordinance expands a lot of definitions for trees and increases regulations for them," said Amanda Zhou, a reporter with the Seattle Times covering the issue.

Trees are regulated based on aspects such as width, species, and the zoning for the property where the tree is located.

In the past code, if a tree was less than 30 inches wide, it had few regulatory protections. Under the new code, trees that are 24 inches or wider face more hurdles for removal. If a tree that is more than one foot in diameter is removed, the city requires a replacement of one or more trees that will eventually grow to have comparable canopy coverage.

If a comparable tree cannot be replaced, developers will pay into a city fund supporting the growth of trees in areas of the city with less canopy cover.

"Seattle is facing more heat waves every summer, and trees do a really good job of absorbing that heat," Zhou said. "So there are key islands throughout the city where it can be up to more than 10 degrees hotter on a hot day — the city wants to use that money to plant trees in areas where they don't really have a canopy."

Estimates show that the new ordinance will affect between 80,000 and 175,000 trees, up from the 17,000 protected under the current city ordinance.

Read Amanda Zhou's reporting on the issue here, and listen to the full Soundside interview by clicking "play" on the audio above.