Member Highlight: Tree Action Seattle Asks Why Seattle's Tree Promises Don't Add Up

Seattle's 2021 Tree Canopy Assessment may be telling residents the wrong story about why the city is losing trees, according to public-records research from GNC member Tree Action Seattle.

The assessment, done by a University of Vermont geospatial team, is the city's central account of the health of its urban forest and has guided city tree policy since its release. Tree Action Seattle recently laid out its findings after filing multiple public records requests about how that report was produced.

At the Green Neighborhoods Coalition, we believe Seattle can welcome new neighbors while protecting the trees and green space that keep our communities healthy and livable. Getting there starts with transparent policymaking built on accurate information.

What Tree Action Seattle found

Tree Action Seattle’s review of the assessment identified five major problems.

1. Development's role in tree loss was downplayed

The report draft named zoning and redevelopment as a primary driver of tree loss and recommended factoring canopy into land use decisions. That draft never reached the public. The final report instead emphasized climate and pests, stating that most of the 870 acres of trees lost in Neighborhood Residential zones were likely lost for reasons other than development.

Other data points the opposite way. KUOW reported that development accounted for 94% of tree removals between 2016 and 2021, and an independent analysis by Oregon State graduate researcher Theodore Hoss found that more than 93% of canopy decline on city parcels occurred on parcels with active permits.

2. Invasive blackberry was counted as canopy

The city measured canopy at a height of 8 feet rather than the widely accepted 10 to 12 feet. As a result, invasive blackberry bushes counted as tree cover: growth on private lots registered as canopy gain and clearing it from parks registered as canopy loss.

3. Parks were blamed for losses that are actually restoration

Tree Action Seattle argues that the low threshold misrepresents restoration work, including blackberry removal and ecological thinning, as canopy decline. Council members have repeatedly cited parks as Seattle’s biggest source of tree loss, while advancing legislation allowing large losses on residential lots and in the right-of-way.

4. Trees' cooling power was understated

The report puts canopy’s cooling effect on hot days at about 1 degree. Tree Action Seattle contrasts that number with findings from NOAA, the USGS, and King County heat mapping showing cooling benefits ranging from 7 to 20 degrees.

5. Canopy volume data was paid for but never released

The study included tree canopy volume measurements, but those findings were not included in the final report. This data is critical to informed policymaking, so leaders understand whether Seattle is losing the density of its tree canopy even where the area it covers appears stable.

Why it matters for our neighborhoods

When Seattle’s leading canopy report points away from development, policy follows. At GNC, we believe every Seattle resident deserves both housing and environmental health. As Seattle grows, new homes must go hand in hand with trees, parks, and green spaces that keep neighborhoods healthy and livable. Achieving that balance requires an honest account of where trees are being lost and why.

Read the full report and evidence

Tree Action Seattle has published the documents behind its findings, including the consulting contract, the unreleased University of Vermont draft, the heat-figure emails, and the 2017 SDCI report. We encourage you to read their full post and look through the evidence.