Urban forest benefits quantified in new report

What are Seattle’s trees doing for you? That’s the focus of a new report on the multi-year effort by the Green Cities Research Alliance to examine the environmental value and benefits of Seattle’s urban forest. Seattle’s Forest Ecosystem Values: Analysis of the Structure, Function, and Economic Values was published in August. The report is the first of its kind for Seattle and found, among other things, that trees save the city about $23 million annually in carbon storage, pollution removal and residential energy savings and that it would cost the city $4.9 billion to replace its trees.

The Alliance is comprised of partners from Forterra, University of Washington, King County, EarthCorps, City of Seattle and the USDA Forest Service. Funding for the research was provided by the U.S. Forest Service Pacific Northwest Research Station and the American Reinvestment and Recovery Act (ARRA). The report was co-authored by Lisa Ciecko, Forterra Green Cities Project Manager; Karis Tenneson, USDA Forest Service, Pacific Northwest Research Station; Jana Dilley, City of Seattle, Seattle reLeaf, Seattle Public Utilities; and Dr. Kathleen Wolf, University of Washington, College of the Environment.

Research was initiated in 2009 with ARRA funding and received additional support from the City of Seattle and Forterra.

“As the findings of this report demonstrate, Seattle’s urban forest provides immense value to the city and its residents,” said Lisa Ciecko, Forterra Green Cities Project Manager. “Having this data will help the City and its partners better manage, care for, and allocate funding to this important resource moving forward.”

Other findings from the report include:

  • There are an estimated 4.35 million trees and tree-like shrubs in Seattle, which equates to a density of nearly 80 trees per acre
  • The three most common species measured were red alder, big leaf maple, and beaked hazelnut, all of which are native to this region.
  • Annually, Seattle trees and tree-like shrubs store an estimated 2 million metric tons of carbon dioxide and sequester 140,000 metric tons of carbon dioxide.
  • Seattle trees remove 725 metric tons of pollution from the environment every year.
  • Seattle’s urban forest reduces energy use in residential buildings by approximately 1.6 million BTUs of natural gas and 43,000 megawatt hours of electricity.

The full report can be found here.

“This kind of information is an invaluable tool for engaging the public in understanding and valuing the importance of our urban trees.” said Jana Dilley, Program Manager for the City of Seattle’s reLeaf program. “The data provided through this research will also help the City move toward our goal of 30% canopy cover in Seattle by 2037.”

Data for the report was collected over a two-year period using the U.S. Forest Service’s i-Tree Eco, its first implementation in Seattle. i-Tree is a suite of tools designed by the U.S. Forest Service that integrates peer-reviewed field methods and analysis software to provide important information on the structure of the forest and key ecosystem service values, information that had not previously been available for urban forest managers and city residents.

In addition to helping the City of Seattle better manage the urban forest, the report will help inform the Green Seattle Partnership’s work. The Partnership is a joint effort by the City of Seattle, Forterra, other local nonprofit organizations and volunteers to restore and steward Seattle’s parks and green spaces. The Partnership works with thousands of volunteers annually to remove invasive plant species, plant native species, build and maintain park trails and more.


Forterra is an unconventional land trust that works across Washington’s communities and landscapes, from the ranches and shrub-steppe of the Yakima basin, to the estuaries, farms and forests of Washington’s coast, reaching more than 100 counties, cities, towns and rural communities. Working cooperatively with people and nature, Forterra drives land stewardship, management and planning; innovative programs and policies; farming and forestry approaches; community ownership opportunities; and development solutions. Visit

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