Presentation to Seattle City Council

October 13, 2008

Tree Inventory & Canopy Mapping

Seattle City Council Presentation, October 13, 2008

Copy of op-ed Seattle Post-Intelligencer: Seattle’s trees: We

need to know what we have, September 9, 2008

Why we need trees: Environmental/Economic Benefits—tab 1

What is already underway in Seattle— 2

Experience in other urban areas— 3

Seattle Urban Nature — 4

Appendix [The Tree Inventory & Urban Forest Assessment &

Canopy Mapping]—5

Members of the ad hoc Tree Inventory/Canopy Mapping Study Group: David

Miller, Seattle Urban Forest Stakeholders [SUFS]; Cheryl Trivison, SUFS; Kit

O’Neill, SUFS; Sharon London, Seattle Urban Nature; Ilze Jones, SUFS;

Michael Oxman, Arborist/Save Seattle Trees; John Barber, POSA; Richard

Haag, FASLA/Professor Emeritus/SUFS; Olaf Ribiero, Tree

Pathologist/Arborist; Chris Overdorf, Jones & Jones

City staff support: Mark Mead, Senior Forester DPR; Nolan Rundquist, City

Arborist, SDOT; Rob Gala, Council President Conlin’s office; and DPR

Superintendent Tim Gallagher

Why we need trees

Environmental Benefits

Carbon Sequestration

• Carbon—the greenhouse gas. One hundred trees per year remove 5 tons of carbon dioxide from

the air. Source: Sacramento Regional Urban Forest Framework, “GreenPrint.”

• One acre of trees sequesters as much carbon dioxide as a car produces in 26,000 miles. Source:

“How does an urban forest contribute to sustainability?” Seattle Office of Sustainability and Environment

website.

• Conserving energy in buildings reduces carbon dioxide emissions from power plants. E. Gregory

McPherson et al., “Western Washington and Oregon Community Tree Guide: Benefits, Costs, and

Strategic Planning,” Center for Urban Forest Research, USDA Forest Service, Pacific Southwest Research

Station, 18.

• The removal and mulching of dead trees releases 80 percent of their stored carbon into the air

in the year of removal. The concomitant use of vehicles, chain saws, chippers, and other

gasoline- and diesel-powered machines increases the carbon in the air. E. Gregory McPherson et

al., “Western Washington and Oregon Community Tree Guide: Benefits, Costs, and Strategic Planning,”

Center for Urban Forest Research, USDA Forest Service, Pacific Southwest Research Station, 19.

• Shaded parking lots reduce hydrocarbon emissions from parked cars by 18 to 21 percent. Source:

Sacramento Regional Urban Forest Framework, “GreenPrint.”

Air Quality Improvement

• Air pollutants—ozone, nitrogen dioxide, sulfuric oxides, particulates. One hundred trees per

year remove 1,000 pounds of such pollutants. Source: Sacramento Regional Urban Forest

Framework, “GreenPrint.”

• Trees reduce air pollutants by 25 percent in cities. Source: Sustainable Urban Forests Coalition,

“National Agenda for Well Managed Urban Forests.”

• Parking lots—heat islands. Cars parked in lots with 50 percent canopy cover emit 8 percent less

evaporative emissions than cars in lots with only 8 percent canopy cover. Source: David Hitchcock,

AICP, “Cool Houston,” Power Point screen for talk at Houston Advanced Research Center, September

2004.

• One acre of trees provides enough oxygen for 18 people. Source: “How does an urban forest

contribute to sustainability?” Seattle Office of Sustainability and Environment website.

• One tree over a 50-year lifetime generates $31,250 worth of oxygen and $62,000 worth of air

pollution control. Source: Michigan State University, Update Forestry.

Noise Reduction

• Thick strips of vegetation combined with berms and solid barriers can reduce highway noise by 6

to 15 decibels. Plants absorb more high frequency noise (the noise most distressing to people)

than low frequency noise. E. Gregory McPherson et al., “Western Washington and Oregon Community

Tree Guide: Benefits, Costs, and Strategic Planning,” Center for Urban Forest Research, USDA Forest

Service, Pacific Southwest Research Station, 11.

Energy Savings

• Shade for cooling: direct shade and water evaporation from leaves combine to produce cooler

air. Four trees planted around a house can save as much as 30 percent on summer cooling costs.

Source: Alliance for Community Trees, “The Value of Trees.”

• Tree shade that protects houses and other buildings on the east and west helps keep them cool,

for an estimated 36 percent reduction in cooling costs. Source: E. Gregory McPherson et al.,

“Western Washington and Oregon Community Tree Guide: Benefits, Costs, and Strategic Planning,”

Center for Urban Forest Research, USDA Forest Service, Pacific Southwest Research Station, 6.

• Conifer windbreaks buffer houses and other buildings and create a dead air space to reduce

heat loss in winter. Source: “How does an urban forest contribute to sustainability?” Seattle Office of Sustainability and Environment website.

• Deciduous (“solar-friendly”) trees planted on the south of houses and buildings help heat

houses and reduce heating costs. Source: E. Gregory McPherson et al., “Western Washington and

Oregon Community Tree Guide: Benefits, Costs, and Strategic Planning,” Center for Urban Forest

Research, USDA Forest Service, Pacific Southwest Research Station, 6.

• Mature, large trees produce approximately 4 to 6 times the energy savings of small trees.

Source: E. Gregory McPherson et al., “Western Washington and Oregon Community Tree Guide: Benefits,

Costs, and Strategic Planning,” Center for Urban Forest Research, USDA Forest Service, Pacific Southwest

Research Station, 31.

Financial benefits

Water Quality Improvement/Stormwater Flow Reduction

• The greater the tree canopy percentage, the less impervious surface there is. Source: American

Forests, Regional Ecosystem Analysis Puget Sound Metropolitan Area: Calculating the Value of Nature

7/25/98.

• Impervious surfaces increase water temperature (thermal pollution) and pollute water with

lawn fertilizers, oils, and other contaminants that flow into receiving water supplies and increase

costs for building retention ponds and additional stormwater facilities and treating water.

Source: Cheryl Kollin, “Quantifying the contributions of trees and vegetation,” StormWater.

• Tree canopies and root systems naturally filter water supplies and reduce storm water runoff,

flooding, and erosion. Source: Alliance for Community Trees, “The Value of Trees.”

• In heavily forested areas of western Washington, 74 percent of rainfall is released back to the

atmosphere or absorbed into the ground. Source: Kathleen L. Wolf, “Tree investment brings many

happy returns,” Environmental Outlook 2001.

• In the Puget Sound area, the rainfall interception provided by a two-story leafy canopy is

especially important during our rainy winters. A two-story canopy has a leaf area 2 to 8 times

the land area it covers. Source: Sacramento Regional Urban Forest Framework, “GreenPrint.”

• A city’s urban forest can reduce peak storm runoff by 10 to 20 percent. Source: “How does an

urban forest contribute to sustainability?” Seattle Office of Sustainability and Environment website.

• In one Milwaukee neighborhood with 42 percent tree canopy, runoff was reduced by 20

percent. Source: National Arbor Day Foundation, Arbor Day, July/August 2006, 7.

• One tree over a 50-year lifetime recycles $37,500 worth of water and controls $31,250 worth of

soil erosion. Source: Michigan State University, Update Forestry.

Infrastructure Savings

• Shade on asphalt roads and parking lots extends the time between needing to resurface by 50

percent. Such savings on roads can be translated into $30,000 savings per mile for resurfacing.

Source: Sacramento Regional Urban Forest Framework, “GreenPrint.”

Property Value Increases, Increased Tax Revenues, and Increased Gains

• Studies say that four trees on a property can speed its sale by four to six weeks. Source: Alliance

for Community Trees, “The Value of Trees.”

• In Sacramento, a residential mature valley oak may be appraised at $20,000 or more. Source:

Alliance for Community Trees, “The Value of Trees.”

• Trees on property or associated with property increase market value by 3.5 to 7 percent. Source:

E. Gregory McPherson et al., “Western Washington and Oregon Community Tree Guide: Benefits, Costs,

and Strategic Planning,” Center for Urban Forest Research, USDA Forest Service, Pacific Southwest

Research Station, 10.

• Mature trees raise property values by as much as 20 percent. Source: “How does an urban forest

contribute to sustainability?” Seattle Office of Sustainability and Environment website.

Business Gains

• A shaded business district encourages shoppers to linger and to spend more and has been

shown to increase prices consumers will pay by as much as 12 percent. Shoppers will also

increase the number of visits they make to a business. Source: Sacramento Regional Urban Forest

Framework, “GreenPrint.”

• Employees with nature views report 23 percent fewer health ailments, a positive influence on

absenteeism. Source: Kathleen L. Wolf, “Tree investment brings many happy returns,” Environmental

Outlook 2001.

• Quality of place—treed landscapes attracts companies and the best employees. Source: Kathleen

L. Wolf, “Tree investment brings many happy returns,” Environmental Outlook 2001.

Health Gains

• Heat-related deaths have risen dramatically since 1994—in Chicago, for instance, from an

average 3 deaths per year in the years before 1995 to a sudden 15 deaths per year in 1995.

Source: David Hitchcock, AICP, “Cool Houston,” Power Point screen for talk at Houston Advanced

Research Center, September 2004.

• Views of trees and visits to hospital green spaces reduce hospital stays. Source: David Hitchcock,

AICP, “Cool Houston,” Power Point screen for talk at Houston Advanced Research Center, September

2004.

• Trees reduce exposure to cancer-causing ultraviolet radiation. Source: E. Gregory McPherson et al.,

“Western Washington and Oregon Community Tree Guide: Benefits, Costs, and Strategic Planning,”

Center for Urban Forest Research, USDA Forest Service, Pacific Southwest Research Station, 11, 25.

Social Gains/Public Safety

• Treed neighborhoods decrease violent episodes that are associated with mental fatigue.

Kathleen L. Wolf, “Tree investment brings many happy returns,” Environmental Outlook 2001.

• In public housing complexes, outdoor spaces with trees are used significantly more often than

spaces without trees. Trees thus facilitate interactions among residents, contributing to lower

domestic violence and safer, more sociable neighborhood environments. Source: E. Gregory

McPherson et al., “Western Washington and Oregon Community Tree Guide: Benefits, Costs, and

Strategic Planning,” Center for Urban Forest Research, USDA Forest Service, Pacific Southwest Research

Station, 10.

• Traffic calming—research has indicated that the presence of trees in the roadside reduces traffic

stress response (road rage). Kathleen L. Wolf, “Tree investment brings many happy returns,”

Environmental Outlook 2001.

• Along tree-lined transportation corridors, cars are driven more slowly, drivers are more aware,

and human comfort and safety is improved. Source: Sacramento Regional Urban Forest Framework,

“GreenPrint.”

Aesthetic Gains

• Incalculable

Included in the Appendix is information from Washington State Department of Natural Resources

published in TreeLink http://treelink.org/linx/factoid.php . This information sheet includes more

Factoids about economic and environmental tree benefits.

What is already underway in Seattle

City Departments

Seattle Department of Transportation [SDOT] has an inventory underway, consultant is Marshall &

Associates. Currently SDOT is updating 1970 inventory; data collecting to improve maintenance

schedule. Data collected species, location, infrastructure [tree grates/overhead wires, etc.]. See

appendix for sample pages of street trees inventoried as of Sept. 17, 2008. Contact person: Nolan

Rundquist, City Arborist, SDOT. Seattle Department of Parks and Recreation [SDPR] needs a tree by tree

inventory for developed park lands, not necessary for forested park lands; on developed lands there are

approximately 90,000 trees [or more]. A current list of park trees is important in order to manage trees

and maintain them, facilitate planning education of resources [species suited to area]; growing needs

and patterns; target under-treed areas. Contact person: Mark Mead, Senior Forester, DPR.

Seattle Public Utilities [SPU] has an aerial canopy cover analysis underway and some detailed inventory

on a per-project basis. Tree-by- tree inventory is required for stormwater credit program. SPU is using

manual inventory. Seattle City Light originally co-sponsored SDOT inventory. City Light is using 1990-92

inventory data. Seattle Center is a 74 acre campus and is working with SDOT to complete a tree

inventory by the end of 2008. Contact person: Lanye Cubell, Strategic Design Consultant, Department of

Construction and Land Use.

Institutions

University of Washington has 9,074 trees mapped. Data gathered on most trees is diameter at breast

height [dbh], height, coniferous/deciduous, number of stems, if they are memorial trees. About 2,000

trees have been identified to species and of those about 1,000 have also been given condition and

location rating, assessed for cultural, biotic, and structural defects, and identified for maintenance need.

Contact person: Kristine Kenney, Campus Landscape Architect

Neighborhood by Neighborhood

Roanoke Park- Park neighbors made an “unofficial” inventory of trees in the park. The inventory is an

alphabetical list by botanical name, noting whether each tree was mature or sapling, and describing the

location of each tree. Thirteen elms in Roanoke Park are tagged by DPR that identify them as Elms 120

through 128, and Elm 121 [plus other non-sequential #s] in the west lawn of the park is a Heritage Tree.

Six of the tagged elm trees are street trees and six are park trees.

Lake Washington Boulevard Vegetation Management Plan contains an inventory of 1,141 trees in the

“Lakeside MU and Boulevard MU” as well as an inventory of 268 trees on “Mt. Baker Slopes. The two

inventories do not contain the same information, but common to both are: assigned tree#, dbh, height,

condition. Kiwanis Ravine stewards have inventoried some of the trees in the Great Blue Heron nesting

area. Sustainable Capitol Hill is currently working on an area tree tour map of Capitol Hill and a street

tree initiative. The tree tour map will be a completely subjective map of notable/beautiful trees. SCH

has identified the tree candidates for the map and is beginning the process of inventorying them.

Experience in other urban areas

SUFS has reviewed numerous cities’ experiences inventorying trees including Boston, MA, Washington

DC, Hillsboro, OR, and Charlotte, NC. Below is a short comparative summary about of the tree

inventories/tree mapping in these four cities. Most notable are the tree inventories/tree mapping in

Boston, MA and Washington, DC. [Support information for Urban Ecology Institute in Boston and

Casey Trees in Washington DC is included in the appendix.]

Comparative summary: Boston, Washington DC and Hillsboro have community based tree inventories.

Loss of trees [canopy] was the primary reason given for tree inventories in Washington DC, Hillsboro, OR

and Charlotte, NC. Storm water control was Boston’s reason for tree inventorying. It was noted in by

each city that a tree inventory is the first step in the management of a city’s urban forest. Charlotte has

a Tree Commission. A complete citywide tree inventory would be unique.

Boston, Massachusetts: Urban Ecology Institute was the lead for The Greater Boston Urban Forest

Inventory [GBUFI] initiative, developed in response to the importance of urban forest management and

the lack of knowledge about the extent and condition of Boston’s urban forest particularly with regard

to Boston’s urban watershed issues. The inventory included both an analysis of Boston’s overall tree

cover using aerial images and a detailed survey of Boston’s street trees.

A two-pronged approach was used: 1. Aerial photography-based mapping of the Urban Tree Canopy

[UTC] of Boston and 2. City-wide volunteer based street tree inventory; and implemented in 2005-06.

The UTC data were then integrated with city parcel data and a map of impervious surfaces. These data

provided a parcel level breakdown of UTC across the entire city. The collection of the baseline data

helped make the case and also involved many volunteers in becoming aware of the trees among them

through the inventory process. Funding was received from State and Federal sources, augmented with

the logistical and in-kind support of the city.

1. Aerial photography-based mapping—Boston’s Urban Tree Canopy was defined by the extent of

land covered by trees, street trees, trees in parks, trees on private property, and trees on

commercial and institutional grounds. Aerial photography and remote sensing imagery was used

to classify land cover by type including tree canopy cover, pervious surfaces [such as dirt and

grass], water, wetland , and impervious surface. The Forest Opportunity Spectrum [FOS], a

modeling program developed by the USDA Forest Service, was then used to calculate the

existing urban tree canopy and possible additional tree canopy of each of Boston’s sixteen

neighborhood’s land area. The overall canopy cover of Boston is 29% or 8640 acres of the total

land area [29,794 acres]. The current canopy cover of Boston’s neighborhoods ranges from 6%

to 49% of the neighborhood land covered. The possible additional canopy cover for each

neighborhood ranges from 31% to 51% of the neighborhood land covered.

2. Boston’s street tree inventory—was implemented to determine the quantity of trees, the

diversity and composition of species present, the condition of trees [including health, size, etc.],

and location of trees and tree pits. A total of 34,487 street trees and 3449 tree pits were

identified throughout Boston. Sampling of findings, two of the ten most identified tree species

overall were Acer plantoides –Norway Maple and Tilia cordata—Littleleaf Linden; 76% of the

trees were in good health and 6% in poor health. Accordingly, the urban tree canopy analysis

and street tree inventory serve to improve management of current street trees, establish

planting goals for increasing the extent of canopy cover, and identify priority planting zones

throughout Boston.

Tree by tree inventory method divided the City of Boston by neighborhood and then by census

block using GIS data. After training, staff [26 interns backed by professional arborists] and

volunteers worked in teams of 2 or 3 to collect data with handheld computers with customized

ArcPad GIS. The most experienced teams inventoried 200 trees/day. ESRI ArcPad software was

used to collect the inventory data on handheld computers. Data collected: species name,

common name, tree height, number of trunk segments, dbh, crown spread, height to crown,

tree health rating, percent dead rating, wound present, insect damage present, fungi present,

hazardous level of tree leaning present. Quality assurance of data was insured by ground-truth

by experts.

Boston used CITYgreen and the Urban Forests Effects Model [UFORE] to calculate the

environmental benefits of trees. Using these models, Urban Ecology Institute was able to

estimate benefits of the urban forest in terms of storm water mitigation, air quality

improvements and carbon storage and sequestration.

See appendix for GBUFI tables and graphics. Above information was summarized from “State of

the Urban Forest: A Summary of the Extent and Condition of Boston’s Urban Forest”, Spring

2008, Urban Ecology Institute. Contact person: John Walkey, Sustainable Cities Division Director,

Urban Ecology Institute

Washington D.C: Casey Trees received an endowment [Eugene Casey] in 2001 in response to studies

documenting a dramatic loss of tree canopy in DC. One of the first efforts was to organize and conduct a

state-of-the-art GIS inventory of District street trees. In 2002 over 500 volunteers compiled information

on 106,000 trees and planting spaces.

Output: established tree planting goals; priorities for management of tree work; report estimates the

replacement value of DC street trees at $3.6 billion and documents value for air pollution and energy

saving. See Appendix for more information on Casey Trees.

DC street tree inventory: in 2002, 500 citizens used hand held computers and a state-of- the-art

mapping system. Unique interactive mapping site was created with assistance from NYPIRG Community

Mapping Assistance. The pollution values were calculated using the USDA Forest Service Urban Forest

Effects Model.

Hillsboro, Oregon: Planning Department worked with 4-H Club and the local 4-H GIS-GPS Tech Wizard

youth to develop street tree inventory. 400 volunteers use ArcPad software to catalog the type,

condition, size and location of approx. 12,000 trees. The group simply loaded the data in the citywide

GIS at the end of each day. Project began in 2005. Contact person: Dan Rutzick, Hillsboro Planning

Department, http://www.esri.com/news/arcnews/winter0506articles/4h-clubs.html

Charlotte, North Carolina: between 1984 and 2001 Mecklenburg County saw a 127 percent increase in

areas covered by impervious surfaces. Charlotte has a Tree Commission. A green data layer [tree theme]

became part of the city’s central data base in 2004. Coordination with senior urban forestry specialist

and systems analyst from the Engineer Dept. used CITYgreen extension from ESRI Business Partner

American Forests.http://www.esri.com/news/arcnews/summero4articles/charlotte-northcarolina.html

Seattle Urban Nature

Seattle Urban Nature [SUN] is a non-profit organization founded in 1998 to survey and map vegetation

and wildlife habitat on 8,000 acres of public lands in Seattle. Data from the 1999-2000 Seattle Public

Lands Habitat Survey provides land managers and citizens with quantitative information about the city’s

natural resources. This information is the basis for the Green Seattle Partnership [GSP], an effort to

restore all parks throughout the city.

Today, SUN assists community groups, government agencies, non-profit organizations and private

citizens in their efforts to survey, map, restore and maintain urban forests in the Puget Sound region.

Our services include vegetation inventories, vegetation management plans, street tree and landscaped

area surveys, restoration monitoring and volunteer training.

SUN is in a unique position to assist the City of Seattle with a tree inventory for a number of reasons:

1) Our scientific experience includes inventories of urban forests throughout the Puget Sound

region. We have experience designing inventory and monitoring protocols for a wide variety of projects

and conditions, for forested areas and formally landscaped urban settings. In 2006, SUN conducted a

survey of trees within formally landscaped areas for the Seattle Department of Transportation [SDOT],

during the course of which nearly 3,500 trees were measured and updated in SDOT’s tree database.

2) Our experience with database design and data management for ecological data enables us to

provide an easy to access data repository that can incorporate information from multiple locations. SUN

has managed multiple custom-designed databases for numerous projects and has experience sharing

information in a compatible way with proprietary databases such as the Hansen database that the City

of Seattle uses. We also have an on-line platform to share geospatial data with the public. Currently all

the information from the 1999-2000 Seattle Public Lands Habitat Survey is available on our website in an

Interactive Habitat Map, which uses the Google Maps platform.

3) SUN has a long history of working with community groups and volunteers and is a well known and

respected entity within the environmental community. We have conducted trainings and workshops for

many organizations including EarthCorps, Washington Native Plant Society, University of Washington

and community groups. SUN is in a unique position to act as a liaison between government agencies

and volunteers and to create and carry out a volunteer training program to conduct a city-wide tree

inventory.

Appendix:

Tree Inventory, Urban Tree fact sheet

http://www.umass.edu/urbantree/factsheets/3treeinventory.html

The Tree Inventory, Extension Forestry http://www.canr.uconn.edu/ces/forest/fact8.htm

Urban Forest Assessment & Canopy Mapping, NCDC Imaging

http://www.rfpmappingllc.com/Shared/UrbanForestry.pdf

TreeLink- Factoids-[publication from Washington Department of Natural Resources]

http://www.treelink.org/linx/factoid.php

Identified Benefits of Community Trees and Forests, Dr. Rim D. Coder, University of Georgia, October

1996 http://www.coloradotrees.org/benefits/Identified%20Benefits%20of%20Community%20Trees.pdf

GASB 34: Urban Natural Resources as Capital Assets, Dudley R. Hartel, American Forests Publication

http://www.urbanforestrysouth.org/resources/library/Citation.2004-11-03.P194/file_name

Putting trees on the payroll: here’s a greener way to clean up air and water while putting your city’s

books in the black, Editorial Deborah Gangloff

http://www.americanforests.org/productsandpubs/magazine/archives/2003fall/editorial.php

Don’t Sell the Value of Your trees Short, Jim Skieka

http://www.isa-arbor.com/publications/arbNews/pdfs/Jun08-perspectives.pdf

Treeconomics, Linda McIntyre, Landscape Architecture Magazine, February 2008

http://www.fs.fed.us/psw/programs/cufr/products/12/psw_cufr731_LandArchTreeconomics.pdf

Seattle Department of Transportation: sample pages of street trees inventoried September 2008

State of the Urban Forest: A Summary of the Extent and condition of Boston’s Urban Forest, Urban

Ecology Institute, Boston, MA, Spring 2008 [GBUFI tables and graphics] pages 15-16 and 33-

34http://www.urbaneco.org/State%20of%20the%20Urban%20Forest%20Report.pdf

Understanding Washington , DC’s Urban Forest through GIS, Holli Howard, director of Data Gathering

and Analysis, Casey Trees http://www.caseytrees.org/DCs_urbanforest_GISarticle.pdf

The following information was in the body of the document:

PI Editorial: Seattle's trees: We need to know what we have, David Miller/Cheryl Trivison

http://seattlepi.nwsource.com/opinion/378443_treeinventory10.html

Seattle Urban Nature: 1999-2000 survey of Seattle's public lands:

http://www.seattleurbannature.org/Survey/background.html