Research on the Benefits and Drawbacks of City Trees and Street Tree Planning Overview

Transcription

1 Research on the Benefits and Drawbacks of City Trees and Street Tree Planning Overview Dr. Greg McPherson Pacific Southwest Research Station U.S.D.A. Forest Service Davis, CA

2 2 Sustainable 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.

3 3 Overview Public Attitudes Public Investment Least Cost Net Benefits Recent Research on Costs and Benefits Space for Trees Green Streets Why Plan? Davis Community Forest Management Plan

4 4 WSU Survey Results 83% strongly agreed that trees are important to their quality of life Reasons 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)

5 5 Municipal Forest Benefit-Cost Net value of green infrastructure Efficient management Justify budgets Analysis

6 6 Typewriter vs. Computer Computer cost 40X typewriter Least-cost approach leads to decision to purchase typewriter Typewriter Computer Cost $100 $4,000 Decision BUY TYPEWRITER

7 7 Typewriter vs. Computer 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. Cost Value Typewriter $100 $10,000 Computer $4,000 $20,000

8 8 Typewriter vs. Computer Net Benefit = Value Cost Highest net benefit approach leads to the decision to purchase computer Cost Value Net Benefit Typewriter $100 $10,000 $9,900 Computer $4,000 $20,000 $16,000 Decision BUY COMPUTER

9 9 Annual Tree Management Costs $30 $25 $20 $15 $10 $5 $0 N. Mt & Prairie Pacific NW Coastal SoCal Central Valley Large Medium Small

10 Annual Costs by Type 10 for Large Trees $12 $10 $8 $6 $4 $2 $0 Plant Prune Remove Infra&Legal Irrigate Pest & Clean Admin N. Mt & Prairie Pacific NW Coastal SoCal Central Valley

11 11 Value of Annual Benefits $100 $90 $80 $70 $60 $50 $40 $30 $20 $10 $0 N. Mt & Prairie Pacific NW Coastal SoCal Central Valley Large Medium Small

12 Value of Annual Benefits by Type 12 for Large Trees $60 $50 $40 $30 $20 $10 $0 Energy CO2 Air Quality Runoff Aesthetics N. Mt & Prairie Pacific NW Coastal SoCal Central Valley

13 13 Value of Net Annual Benefits $70 $60 $50 $40 $30 $20 $10 $0 N. Mt & Prairie Pacific NW Coastal SoCal Central Valley Large Medium Small

14 14 Benefit-Cost Results Modesto Santa Monica Modesto Santa M. Modesto Santa M. Total $ Total $ $/tree $/tree $/capita $/capita Total Costs 2,623,384 1,544, Total Benefits 4,848,140 2,349, Net Benefits 2,224, , Benefit/Cost

15 15 Summary of Benefit-Cost Analysis 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 - $25 Large tree $20 - $60 Net benefits increase with tree size Benefit-cost ratios 1.5 to 1.9 $/Tree $80 $70 $60 $50 $40 $30 $20 $10 $0 Modesto Tree Age in Years Energy CO2 Air Quality Stormwater Aesthetic

16 Effects of Tree Shade on 16 Pavement 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 performance Finding: Greater tree shade correlated with better pavement performance 20% shade increase improves pavement condition by 11%

17 17 Modesto Economic Analysis 30-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.)

18 18 Results Street CD (ft) TSI Slurry Seals Cost ($) Hackberry ,440 C. Myrtle ,600

19 19 Benefit-Cost Profiles by Species Toital Annual Benefits per Tree Total Annual Costs per Tree $/tree $/tree Sweetgum Mod. Ash Hackberry Zelkova >60 Sweetgum Mod. Ash Hackberry Zelkova >60 Camphor Plane Camphor Plane Pistache Pistache Ginkgo S. Magnolia Pear Ginkgo S. Magnolia 0-10 Pear dbh (cm) dbh (cm)

20 20 Average Annual Net Benefits $250 Average Annual Net Benefits per Tree $200 $150 $100 $50 $0 -$ dbh (inches) Zelkova Ginkgo Pear

21 21 Benefit-Cost Ratios by Species in Modesto Species Plane Gingko Zelkova Hackberry Ash Pistache Pear Sweetgum Benefit-Cost Ratio

22 22 Tree selection Uses for This Type of Increasing benefits Reducing costs Projecting future benefits and costs associated with aging populations Justifying funding for tree health and longevity Information

23 Controlling Costs: 23 Inadequate Space for Trees

24 24 Smart Growth and Streetscapes 3 to 5 foot border area or grass strip... (ULI, 2001) Safety from traffic Trash receptacles Driveway gradient Snow storage Less splash Planting space

25 Remain a Victim? ROW Design 25 Where Trees Are Incidental

26 26 Solution: Green Streets Narrower street widths Increase planting strip width to 8 ft for large widespreading trees Create swales with berms for stormwater treatment Stormwater benefits: Runoff reduction Detention Lower water temperature Less pollutant loading Phytoremediation

27 27 Energy and Other Benefits Savings 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 Temperature ( deg. F ) Low canopy Medium canopy High canopy Making Room for Trees More high-yield tree sites Saves money for developers, local governments, and residents Hour of Day

28 28 Green Street Solutions

29 Green 29 Street Retrofit Increase planting strip (4 8 ) Pervious parking areas Narrow travel lane (22 11 ) Result Impervious Reduced 84% to 21%

30 30 3 Key Components of Street Tree Programs Policies, Plan, Ordinances, and Specifications Municipal forester - knows management needs and allocates resources efficiently Public awareness, support and participation

31 Plans, Ordinances, 31 Standards, Specifications

32 32 Street Tree Management Professional urban forester Inventory Management Plan Efficiency and Safety Training

33 33 Public Awareness & Support Tree Commission Tree City/Arbor Day Non-Profit City-businesscitizen cooperation

34 34 Why Plan? Provide the best SERVICE possible Most efficient use of resources Maximize net benefits of trees Increase customer satisfaction Improve flexibility to respond

35 35 Street Tree Planning Process What 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

36 Davis Community Forest 36 Overview Management Plan Context: Existing Conditions History of Tree Management Administration and Management State of the Community Forest Community Forest Goals, Policies, Standards and Actions Glossary Appendices

37 37 Davis Community Forest Management Plan: Overview Vision Statement Benefits and Value of Community Forest Management Goals and Priorities Funding Sources

38 38 Davis Community Forest Management Plan: Context Early and Recent History of Tree Management Administration and Management Existing Laws, Policies and Standards Stewardship (Council, Commissions, City Departments, Non-Profit, Utilities) Current Tree Program Staffing and Resources State of the Community Forest Structure and Health Planting and Management Needs Benefits and Costs

39 39 Davis Community Forest Management Plan: Goals, Policies, Standards and Actions Improve quality of community forest to optimize benefits Promote planting preservation and protection of existing trees Continue to maintain trees in a safe and healthy condition as cost-effectively as possible Facilitate collaboration among City departments Educate the community on proper tree care and encourage participation Adopt the Plan and update every five years

40 40 Goal 3: Continue to maintain trees in a safe and healthy condition as cost- effectively as possible Policy 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 Specifications Policy 3.6: Develop and implement tree removal and replacement plans in areas where significant loss of tree canopy is likely

41 Linking Street Tree Planning 41 and 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 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 Budget Analysis ID Levels of Service Budget for Optimal LOS Budget for Other LOS Recommend LOS

42 42 Summary Trees Have Popular Appeal Net Benefit vs. Least Cost Approach Larger Trees = Greater Net Benefits Species 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