Research on the Benefits and Drawbacks of City Trees and ... · Center for Urban Forest Research. Effects of Tree Shade on . 16. Pavement Performance. z. Well-shaded streets may deter

Research on the Benefits and Research on the Benefits and Drawbacks of City Trees and Street Drawbacks of City Trees and Street

Tree Planning OverviewTree Planning Overview

Dr. Greg McPhersonCenter for Urban Forest Research

Pacific Southwest Research StationU.S.D.A. Forest Service

Davis, CAhttp://cufr.ucdavis.edu

Center for Urban Forest ResearchCenter for Urban Forest Research

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Center for Urban Forest ResearchCenter for Urban Forest ResearchSustainable Urban Forest EcosystemsSustainable Urban Forest Ecosystems

Maximize net benefits for current and future generations.– Controlling costs– Increasing benefits

Convert research results into financial terms to stimulate community investment in trees.


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OverviewOverviewPublic AttitudesPublic Investment– Least Cost– Net Benefits

Recent Research on Costs and BenefitsSpace for Trees –Green StreetsWhy Plan?Davis Community Forest Management Plan


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WSU Survey ResultsWSU Survey Results83% strongly agreed that trees are important to their quality of lifeReasons to have trees– Shade and cool surroundings (3.69)– Help people feel calmer (3.56)– Reduce smog and dust (3.49)– Reduce noise (3.36)

Problems with trees– Cause allergies (1.64)– Block store signs (1.57)– Roots crack sidewalks (1.50)– Can fall across power lines (1.44)– Cost city too much (1.3)


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Municipal Forest BenefitMunicipal Forest Benefit--Cost Cost AnalysisAnalysis

Net value of green infrastructureEfficient managementJustify budgets


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Typewriter vs. Computer Typewriter vs. Computer -- 19851985

$4,000$100Cost

ComputerTypewriterComputer cost 40X typewriterLeast-cost approach leads to decision to purchase typewriter BUY

TYPEWRITERDecision


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Typewriter vs. Computer Typewriter vs. Computer -- 19851985

Compare Value:– Employee makes $50K/

yr– Spends 30% time writing

memos by hand– Typewriter reduces time

to 20%– Computer reduces time

to 10%– Computer & typewriter

last 2 yrs.

$20,000$10,000Value

$4,000$100Cost

ComputerTypewriter


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Typewriter vs. Computer Typewriter vs. Computer -- 19851985Net Benefit = Value – CostHighest net benefit approach leads to the decision to purchase computer

$4,000$100Cost$20,000$10,000Value$16,000$9,900Net Benefit

ComputerTypewriter

BUYCOMPUTER

Decision


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Annual Tree Management CostsAnnual Tree Management Costs

$0

$5

$10

$15

$20

$25

$30

N. Mt & Prairie Pacific NW Coastal SoCal Central Valley

Large Medium Small


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Annual Costs by TypeAnnual Costs by Typefor Large Treesfor Large Trees

$0

$2

$4

$6

$8

$10

$12

Plant

Prune

Remov

e

Infra&Le

gal

Irriga

tePes

t & C

lean

Admin



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Value of Annual BenefitsValue of Annual Benefits

$0$10$20$30$40$50$60$70$80$90

$100


Large Medium Small


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Value of Annual Benefits by TypeValue of Annual Benefits by Typefor Large Treesfor Large Trees

$0

$10

$20

$30

$40

$50

$60

Energy CO2 Air Quality Runoff Aesthetics



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Value of Net Annual BenefitsValue of Net Annual Benefits

$0

$10

$20

$30

$40

$50

$60

$70


Large Medium Small


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BenefitBenefit--Cost ResultsCost ResultsModesto Santa Monica Modesto Santa M. Modesto Santa M.

Total $ Total $ $/tree $/tree $/capita $/capitaTotal Costs 2,623,384 1,544,000 28.77 52.82 14.39 16.68 Total Benefits 4,848,140 2,349,732 53.17 80.39 26.60 25.38 Net Benefits 2,224,756 805,732 24.40 27.57 12.21 8.70 Benefit/Cost 1.85 1.52


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Summary of BenefitSummary of Benefit--Cost Cost Analysis ResultsAnalysis Results

Mature street tree– Annual Benefits $40 - $80

Aesthetics, air quality, runoff– Annual Costs $15 - $30

Prune, plant, hardscape repair– Net Benefits

Medium tree $10 - $25Large tree $20 - $60

Net benefits increase with tree sizeBenefit-cost ratios 1.5 to 1.9

Modesto

$0$10$20$30$40$50$60$70$80

5 15 25 35 45 55Tree Age in Years

$/Tr

eeEnergy CO2 Air Quality Stormwater Aesthetic


16Effects of Tree Shade on Effects of Tree Shade on Pavement PerformancePavement Performance

Well-shaded streets may deter aging of pavement– Volatilization: loss of lighter weight

volatiles by evaporation or degradation

Hypothesis: There is a positive relation between tree shade and asphalt pavement performanceFinding: Greater tree shade correlated with better pavement performance– 20% shade increase improves

pavement condition by 11%


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Modesto Economic AnalysisModesto Economic Analysis30-year repaving costs for identical street segments – 30 yrs after

construction– 125’ x 35’ segment– Low shade (12 crape

myrtle, 25’ O.C., 15’ C.D.)

– High shade (6 hackberry, 50’ O.C., 45’ C.D.)


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ResultsResults

3,6005915C. Myrtle1,44024145Hackberry

Cost ($)

SlurrySealsTSI

CD (ft)Street


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BenefitBenefit--Cost Profiles by SpeciesCost Profiles by Species

0-10

10-2020

-3030-4646

-60>60

Sweetgum

Mod. Ash

Hackberry

Zelkova

Camphor

Plane

Pistache

Ginkgo

S. Magnolia

Pear

050100150200250

300

350

$/tre

e

dbh (cm)

Toital Annual Benefits per Tree

0-10

10-2020

-3030-4646

-60>60

Sweetgum

Mod. Ash

Hackberry

Zelkova

Camphor

Plane

Pistache

Ginkgo

S. Magnolia

Pear

020406080

100120

140

$/tr

ee

dbh (cm)

Total Annual Costs per Tree


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Average Annual Net BenefitsAverage Annual Net Benefits

-$50

$0

$50

$100

$150

$200

$250

0-4 4-8 8-12 12-18 18-24 24+dbh (inches)

Average Annual Net Benefits per Tree

Zelkova Ginkgo Pear


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BenefitBenefit--Cost Ratios by Cost Ratios by Species in ModestoSpecies in Modesto

2.6Pear

2.4Sweetgum

3.3Pistache

3.6Ash

5.5Hackberry

5.9Zelkova

7.4Gingko

24.3PlaneBenefit-Cost RatioSpecies


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Uses for This Type of Uses for This Type of InformationInformation

Tree selectionIncreasing benefitsReducing costsProjecting future benefits and costs associated with aging populationsJustifying funding for tree health and longevity


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Controlling Costs: Controlling Costs: Inadequate Space for TreesInadequate Space for Trees


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Smart Growth and Smart Growth and StreetscapesStreetscapes

“3 to 5 foot border area or grass strip...” (ULI, 2001)– Safety from traffic– Trash receptacles– Driveway gradient– Snow storage– Less splash– Planting space


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Remain a Victim? ROW Design Remain a Victim? ROW Design Where Trees Are IncidentalWhere Trees Are Incidental


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Solution:Solution:Green StreetsGreen Streets

Narrower street widthsIncrease planting strip width to 8 ft for large wide-spreading treesCreate swales with berms for stormwater treatmentStormwater benefits:– Runoff reduction– Detention– Lower water temperature– Less pollutant loading– Phytoremediation


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Energy and Other BenefitsEnergy and Other BenefitsSavings from Narrower, Tree Shaded Streets– 15% home cooling costs– $60,000/mile paving – 50% for street resurfacing – Improved human comfort

and air quality– Calmer streets

Making Room for Trees– More high-yield tree sites – Saves money for

developers, local governments, and residents

50

55

60

65

70

75

80

85

90

95

100

105

0 4 8 12 16 20

Hour of Day

Tem

pera

ture

( de

g. F

)

Low canopy

Medium canopy

High canopy


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Green Green Street Street

SolutionsSolutions


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Green Green Street Street RetrofitRetrofit

Increase planting strip (4’ – 8’)Pervious parking areasNarrow travel lane (22’ – 11’) Result– Impervious Reduced

84% to 21%


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3 Key Components of 3 Key Components of Street Tree ProgramsStreet Tree Programs

Policies, Plan, Ordinances, and SpecificationsMunicipal forester -knows management needs and allocates resources efficientlyPublic awareness, support and participation


31Plans, Ordinances, Plans, Ordinances, Standards, SpecificationsStandards, Specifications


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Street Tree ManagementStreet Tree Management

Professional urban foresterInventoryManagement PlanEfficiency and SafetyTraining


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Public Awareness & SupportPublic Awareness & SupportTree CommissionTree City/Arbor DayNon-Profit City-business-citizen cooperation


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Why Plan?Why Plan?Provide the best SERVICE possible

– Most efficient use of resources

– Maximize net benefits of trees

– Increase customer satisfaction

– Improve flexibility to respond


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Street Tree Planning ProcessStreet Tree Planning ProcessWhat Do We Have?

•Vegetation Resource•Vegetation Management•Community Framework

What Do We Want?•Vision

• Long-term Goals (5-10 years)•Short-term Goals (3-5 years)

•Annual Goals

How Do We Get What We Want?• Policies, Ordinances, Standards

• Funding Options• Public Outreach


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Davis Community Forest Davis Community Forest Management PlanManagement Plan

OverviewContext: Existing Conditions– History of Tree Management– Administration and Management– State of the Community Forest

Community Forest Goals, Policies, Standards and ActionsGlossaryAppendices


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Davis Community Forest Davis Community Forest Management Plan: OverviewManagement Plan: Overview

Vision StatementBenefits and Value of Community ForestManagement Goals and PrioritiesFunding Sources


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Davis Community Forest Davis Community Forest Management Plan: ContextManagement Plan: Context

Early and Recent History of Tree ManagementAdministration and Management– Existing Laws, Policies and Standards– Stewardship (Council, Commissions, City

Departments, Non-Profit, Utilities)– Current Tree Program Staffing

and ResourcesState of the Community Forest– Structure and Health– Planting and Management Needs– Benefits and Costs


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Davis Community Forest Davis Community Forest Management Plan: Goals, Policies, Management Plan: Goals, Policies,

Standards and ActionsStandards and ActionsImprove quality of community forest to optimize benefitsPromote planting preservation and protection of existing treesContinue to maintain trees in a safe and healthy condition as cost-effectively as possibleFacilitate collaboration among City departmentsEducate the community on proper tree care and encourage participationAdopt the Plan and update every five years


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Goal 3: Continue to maintain trees in Goal 3: Continue to maintain trees in a safe and healthy condition as costa safe and healthy condition as cost--

effectively as possibleeffectively as possiblePolicy 3.1: Develop a Master Street Tree Plan– Standard A. Review City Master Tree List every 5

years– Standard B. Desired age structure is 40% young,

30% maturing, 20% mature, 10% old– etc.

Policy 3.2: Develop Tree Planting and Maintenance SpecificationsPolicy 3.6: Develop and implement tree removal and replacement plans in areas where significant loss of tree canopy is likely


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Linking Street Tree Planning Linking Street Tree Planning and Budgetingand Budgeting

Tree Inventory & Analysis• Sample or Full

• Structure and Health• Management Needs

• Annual Benefits

Management Needs Assessment• Planting

• Small Tree Care• Large Tree Care

• Removal• Administration

• Prioritize Needs

Budget Analysis• ID Levels of Service

• Budget for Optimal LOS• Budget for Other LOS

• Recommend LOS

Project Budget Consequences• Costs of Deferred Maintenance

• Storm damage (stop-gap)• Tree failures• Pruning/removal costs

• Benefits Foregone• Fewer trees• Smaller trees• Less healthy trees


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SummarySummary

Trees Have Popular AppealNet Benefit vs. Least Cost ApproachLarger Trees = Greater Net BenefitsSpecies Makes a Difference Green Streets – Space for Large Trees– Revise street design standards– Win-Win for developers, city, residents

Davis Plan links budgeting with management– http://www.cityofdavis.org/pcs/trees/cfmp.cfm

Documents

Research on the Benefits and Drawbacks of City Trees and ... · Center for Urban Forest Research. Effects of Tree Shade on . 16. Pavement Performance. z. Well-shaded streets may deter