Questions about Seattle, Washington’s 30% Tree Canopy Goal

In 2007, Seattle, Washington in their Urban Forest Management Plan set a goal  to reach a 30% canopy cover by 2037. The most current canopy cover analysis done in 2016 stated that Seattle has a canopy cover of 28%. Several issues with this study. Canopy was measured at eight feet above the ground which includes many shrubs that grow over 8 feet tall like laurel and holly and other hedge shrubs. Many of these are also invasive plants in Seattle.
An additional issue is that the true measure of canopy value is canopy volume in terms of ecosystems services, not canopy area. Small trees planted to replace a 100 tall Douglas fir or western red cedar may cover the same surface area but will never replace the benefits that mature large trees provide.
The current canopy cover goal was a 30-year goal set in 2007 in the Urban Forest Management Plan that was added in Seattle’s Comprehensive Plan. They were estimating at  that time that the current canopy cover was at 18% and to reach a 30% canopy they needed to plant some 649,000 more trees. What does not appear to be considered is tree survivability and replacement tree species (size) or when the  trees needed to be planted to grow to the desired canopy cover. Trees planted 30 years ago would have had 14 years of growth to date and in 2037 be over 30 years old. Trees planted in 2030 would only have 7 years of growth toward the canopy goal.
“How Did We Derive Cover Goals? 
 
American Forests, a leading urban forest management, conservation and research group, measured tree cover in 440 communities. Their research recommends that a canopy cover goal of 40% would be appropriate for Seattle and other cities in the Pacific Northwest.
In developing canopy cover goals for Seattle, the Urban Forest Coalition started with the American Forests recommendation and went through the following process to define an ambitious but doable goal for the Urban Forest Management Plan 30-year planning horizon (Table 5):
 • Considered American Forests’ recommendations and benchmarked with other cities 
• Considered land-use mix in Seattle and other City land-use goals (e.g. encouraging density, facilitating freight mobility, etc.)
 • Considered current canopy cover and planting opportunities 
• Defined goals for each land-use type 52
 • Factored in the percentage of the total land base within each land-use type and individual land-use goals to calculate the recommended citywide goal of 30%
 • Consulted with external experts from other cities, consultants, the University of Washington, and the public.”
Table 5. Canopy Cover Goals by Management Unit (MU)* – see page 58 
Table 7. City Wide Management Unit Data – see page 68
 
also – Canopy Cover Goals for Seattle by Management Unit – see page 14
 
American Forests recommended a 40 % canopy goal for most cities at that time.
 Seattle was mistakenly stated by some to have a 40 % canopy around then. The canopy analysis done by American Forests at the time was on King County, not Seattle specifically. All of Seattle, except for Schmitz Park and Seward Park, has been clearcut, is second or third growth and was not at 40% in the 70’s.
In 2017 American Forests released the following – “Why We No Longer Recommend a 40% Urban Tree Canopy Goal” The article basically says one size does not fit all because of varying state environmental conditions.
The good news for Seattle is the following statement in that article – “Within those parameters, quantifiable data can be used so a tree canopy goal achieves specific objectives, such as reaching the canopy percentage necessary to reduce urban heat island temperatures to a specific range, or to reduce stormwater runoff by a projected amount. According to a national analysis by U.S. Forest Service researchers David Nowak (also on our Science Advisory Board) and Eric Greenfield, a 40-60 percent urban tree canopy is attainable under ideal conditions in forested states.”
 
The UFC supported and pushed for maintaining an aspirational goal of 40% canopy cover in Seattle in the latest Comprehensive Plan but be certain the city will probably again try to remove this goal. Seattle is currently working on updating their Comprehensive Plan with a release in 2024 state deadline. Minimally the UFC should push for 30% by 2030 which allows for 9 years of growth of trees planted in 2021 and retaining as many existing trees as possible. The 2030 timeline fits with the city’s other adopted ambitious climate goals being set for 2030. We do have a climate crisis and the city has no set plan as to how it can reach 30% besides planting maybe several thousand trees a year on private property. We do not need to wait for another LIDAR study. We have a significant lack of trees in south Seattle that needs to be addressed regardless of what our current canopy citywide is. It is an environmental justice and equity issue because higher temperatures due to the Heat island Effect can and does kill people..
 
Here are some tree canopy cover figures for other cities in Washington State and around the US on the Friends of Seattle’s Urban Forest website –   Canopy Cover 
The current 30% goal is actually a macro goal. In terms of tree canopy needs, where trees need to be planted is in low canopy areas, which are mostly low income and minority areas, which in large part correlates with previously redlined areas. Also industrial areas have low canopy. These areas are also the ones that have experienced the greatest heat island impacts – which can be deadly to people living and working there.   What is really needed is a targeted goal to add trees and canopy in to these low canopy areas that are low income and BIPOC communities in south Seattle that are identified by higher temperatures caused by the heat island impacts.
As part of Seattle’s climate crisis response it needs to target these low canopy areas. It needs to set a goal to plant and grow the needed trees there. The timeframe needs to be shortened to 2030 to match other city goals to address the climate crisis response by 2030.

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