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Understanding Tree Canopy Cover and Its Role in Urban Forest Conservation

Eric Wiseman
February 19, 2022

Understanding Tree Canopy Cover and Its Role in Urban Forest Conservation

Presentation given at the 18th Annual EcoSavvy Symposium hosted by Fairfax County Master Gardeners.

Eric Wiseman

February 19, 2022
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  1. Understanding Tree Canopy Cover and
    Its Role in Urban Forest Conservation
    P. Eric Wiseman, PhD
    Associate Professor of Urban and Community Forestry
    Dept. of Forest Resources and Environmental Conservation
    Virginia Tech
    [email protected]
    linktr.ee/EricWiseman
    @vtarborist
    Source: www.dronegenuity.com/aerial-photography/virginia/
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022

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  2. Presentation Outline
    02  37
    o What is tree canopy cover and why is it
    important to urban environments?
    o What do we know about tree canopy cover in
    urban areas of Virginia?
    o What are threats and challenges to
    sustaining tree canopy cover in urban areas?
    o How can we measure and monitor tree
    canopy cover in urban areas?
    o What are key strategies for conserving tree
    canopy cover in urban areas?
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022

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  3. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    Urban Forests and Why They Matter
    03  37

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  4. Urban Forests and Why They Matter
    Source: www.oufc.org/2021/06/05/announcing-2020-tree-cities-of-the-world
    Trees and associated natural resources found in and
    around an area of dense human development
    Source: www.whiterockcity.ca/484/Urban-Forest-Management-Plan
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 04  37

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  5. Urban Forests and Why They Matter
    Community
    cohesion
    Source: ourauckland.aucklandcouncil.govt.nz/news/2019/03/knowing-
    growing-and-protecting-a-flourishing-urban-forest-for-auckland/
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 05  37

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  6. Urban Forests and Why They Matter
    • Overall, there are an estimated 5.5 billion trees in US
    urban areas, which equates to 22.2 trees per capita.
    • In US cities, about 1 in 3 trees have been planted.
    • Planting accounts for the majority of trees in residential
    (75%) and commercial (61%) areas.
    • Natural regeneration on vacant lands is a major
    contributor to tree cover in the forest ecoregion.
    Source: Nowak, D. J., & Greenfield, E. J. (2018). US urban forest statistics, values, and projections. Journal of Forestry, 116(2), 164-177.
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 06  37

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  7. The layer of tree foliage, branches, and stems that
    overhangs the ground when viewed from above
    Source: www.google.com/earth
    • Foliage is the key component of canopy
    because it provides most of the surface area
    for shade, interception, and absorption
    • We usually think of tree canopy as 2-D, but
    keep in mind that it is actually 3-D
    • Tree canopy is dynamic in both space and
    time due to regeneration, growth, mortality,
    and land use change
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Is Tree Canopy Cover?
    07  37

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  8. The most basic measure of tree canopy cover is the percentage of
    the total land area covered by canopy
    Source: Plan-It Geo, Urban Tree Canopy Assessments Source: Plan-It Geo, Urban Tree Canopy Assessments
    35%
    10%
    30%
    5%
    10%
    5%
    0%
    0%
    0%
    5%
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Is Tree Canopy Cover?
    08  37

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  9. Source: www.thoughtco.com/where-us-forests-are-located-1343035 Source: Nowak, D.J., et al. (2010). US Forest Service GTR NRS-62.
    Forest Cover Urban Tree Canopy Cover
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Is Tree Canopy Cover?
    09  37

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  10. Data Source: Nowak, D. J., & Greenfield, E. J. (2018).
    Declining urban and community tree cover in the United
    States. Urban Forestry & Urban Greening, 32, 32-55.
    Chart Source: www.deeproot.com/blog/blog-
    entries/the-latest-urban-tree-canopy-cover-by-state
    National UTC Average (2014):
    39.4%
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Is Tree Canopy Cover?
    10  37

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  11. Source: Nowak, D. J., & Greenfield, E. J. (2012). Tree and impervious cover
    in the United States. Landscape and Urban Planning, 107(1), 21-30.
    Although tree cover accounts for 66% of VA’s land cover,
    urban tree cover only accounts for 6% of total tree cover.
    VA urban tree cover circa 2014 averaged 45.2%.
    This equates to about 772 thousand acres of
    urban tree cover and 166 million urban trees.
    Source: coopercenterdemographics.files.wordpress.com/2014/03/current.jpg
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Is Tree Canopy Cover?
    11  37

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  12. Remote Sensing: Analysis of imagery and LiDAR acquired by sensors from above
    How Is Tree Canopy Cover Assessed?
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 12  37

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  13. The Process: Computerized Image Analysis and Land Cover Classification
    Hyperspectral Image:
    Red, Green, Blue
    Infrared
    LiDAR
    Land Cover Map
    Source: vtcommunityforestry.org/resources/inventories-management-plans/tree-canopy-assessments
    How Is Tree Canopy Cover Assessed?
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 13  37

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  14. The Product: Data describing canopy amount, distribution, and ownership
    Source: www.charlottesville.gov/Archive/ViewFile/Item/97
    How Is Tree Canopy Cover Assessed?
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 14  37

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  15. It’s a straight-forward concept and metric for allied
    professionals and the general public to understand
    • Tree canopy is strongly linked to urban
    ecosystem function and human well-being
    • Tree canopy cover can be efficiently quantified
    and characterized over large geographic areas
    with high spatial resolution
    • Tree canopy cover data can be utilized in land
    use planning and environmental policy
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    Why Do We Emphasize Tree Canopy Cover?
    15  37

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  16. DIRECT THREATS INDIRECT THREATS
    o Forest Land Conversion (sprawl)
    o Urban Infill Development (density)
    o Lack of Green Infrastructure Plan
    o Improper Greenspace Design
    o Limited Management Resources
    o Inadequate Tree Protection BMPs
    o Lack of Re-Planting Trees
    o Climate Change
    o Invasive Pests and Plants
    o Urban Stress Factors
    - Heat and Drought
    - Degraded Soil
    - Pollution & Disturbance
    Source: stock.adobe.com/search/images?k=land+development&asset_id=225938293
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    16  37

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  17. Percentage Change in Urban Land Use, 1997 to 2060
    30 to 43 million acres of land in the South
    Source: www.srs.fs.usda.gov/compass/2014/10/09/projected-land-use-change-in-the-south
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    17  37

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  18. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    Source: vanhde.org/content/map
    What Are Threats to Tree Canopy Cover?
    18  37

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  19. Source: vanhde.org/content/map
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    19  37

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  20. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    Source: www.mrlc.gov/viewer
    20  37

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  21. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    Source: www.mrlc.gov/viewer
    21  37

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  22. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    Source: www.mrlc.gov/viewer
    22  37

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  23. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    23  37

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  24. Year 2009 to 2014
    Tree cover in US urban areas
    declined at rate of 138,000 acres
    annually, about 28 million trees
    per year
    Lost $96 million in annual ecosystem services
    Virginia lost 4,270 acres of urban tree cover
    annually, about 878 thousand trees per year, and
    $2.5 million in annual ecosystem services
    Source: Nowak, D. J., & Greenfield, E. J. (2018). Declining urban and community tree
    cover in the United States. Urban forestry & Urban Greening, 32, 32-55.
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    24  37

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  25. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    Source: www.ajc.com/neighborhoods/dekalb Source: saportareport.com
    25  37

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  26. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    Source: www.cbf.org/news-media/newsroom/2022/virginia Source: lis.virginia.gov/cgi-bin/legp604.exe?ses=221&typ=bil&val=sb537
    26  37

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  27. Source: stevekingonsustainability.blogspot.com, March 10 2013
    Space for large-maturing,
    long-lived, healthy trees?
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    27  37

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  28. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    28  37

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  29. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    What Are Threats to Tree Canopy Cover?
    Source: www.bloomberg.com/news/features/2021-07-30/what-happens-after-pledges-to-plant-millions-of-trees Source: www.fs.fed.us/psw/topics/urban_forestry/products/cufr_511_large_tree_argument.pdf
    29  37

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  30. Mission: To promote the care and
    appreciation of trees – big and small
    Document the largest
    specimens in the state and
    provide resources to aid in
    their protection and care
    Maclura pomifera**
    Charlotte Co.
    65’
    93’
    328”
    416 pts.
    Photo credit: A. Cassell
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    The Virginia Big Tree Program
    30  37

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  31. The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    The Virginia Big Tree Program
    31  37

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  32. Quercus pagoda**
    City of Portsmouth
    114’ height
    138’ crown spread
    331” trunk girth
    480 pts.
    o Register comprises a searchable online
    database plus an historical record archive
    o Currently curate the top-three* specimens of
    any native or non-native tree species (and
    verifiable sub-species and varieties)
    o Minimum eligible tree size:
    ≥ 13’ height and ≥ 9.5” trunk circumference
    o Trees must be re-certified every ten years to
    remain active in the register
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    The Virginia Big Tree Program
    32  37

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  33. o 116 counties and independent cities have 1 or
    more big trees in the register
    o Currently 1,539 living specimens across 474
    species are curated in the register
    o Currently 91 national champs/co-champs,
    top-3 most champs in country
    *not all trees shown due to privacy policy
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022
    The Virginia Big Tree Program
    33  37

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  34. CONSERVE EXISTING COVER
    “Take care of what you’ve got!”
    REPLENISH NEW COVER
    “Plant trees!”
    Intrinsic Motivations
    Property Value
    Commerce
    Health & Well-Being
    Educate People About:
    Consequences of Loss
    Extrinsic Motivations
    Zoning
    Ordinances
    Resource Protection Areas
    Conservation Easements
    Financial Inducements
    How Do We Sustain Tree Canopy Cover?
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 34  37

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  35. Community
    Industry
    Government
    Scientists
    Professionals
    o Urban forests require space
    o Urban forests require funding
    o Urban forests require monitoring
    o Urban forests require advocates
    o Urban forests require planning
    o Urban forests require expertise
    But It Is Not That Simple…
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 35  37

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  36. Municipal
    Non-Profit
    Residential
    Commercial
    Framework for
    Stewardship
    Investment in
    Stewardship
    Space for
    Stewardship
    Advocacy for
    Stewardship
    Partnerships For Sustaining Tree Canopy
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 36  37

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  37. Take Home Messages
    o Tree canopy cover is strongly correlated to
    benefits of the urban forest
    o Livability and sustainability of urban areas
    depends on conservation and management of
    tree canopy cover
    o Land development without careful
    consideration for protecting and replenishing
    trees is a primary cause of canopy loss
    o Tree canopy stewardship requires commitment,
    partnership, and action by multiple
    stakeholder groups
    The 18th Annual EcoSavvy Symposium • Alexandria, VA • February 19, 2022 37  37

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