• Start-up
  • Planning
  • Action
  • Evaluation
The urban forest in Fairfax County faces many threats including development, invasive species, and changing environmental conditions due to climate change. The Fairfax County Urban Forest Management Division is evaluating how we can make better tree planting and preservation recommendations as well as natural resource management decisions in Fairfax County.

Project Area

Map showing the outline of Fairfax County in relation to Maryland and Washington, DC
Fairfax County is located within the DC Metro area with a population of over 1.1 million residents. There has been expansive development over the past 40 years. It is a suburban community that is increasingly becoming more urbanized. The population is projected to increase over the next several decades which we are anticipating will lead to continued urbanization. As of 2015, Fairfax County has 54.7% tree canopy according to analysis from satellite imagery and LIDAR.

Management Goals

Residential goal: Protect and improve tree canopy in Fairfax County in residential communities

  • Objectives:

    • Maintain the 54.7% tree canopy (1 year)

    • Plant 5000 trees on residential properties per year across the county (1 year)

Fairfax County goals:

  • Conserve and improve the quality of existing tree canopy on sites undergoing land development

  • Manage nonnative/invasive species that threaten trees and the urban forest community.

  • Objectives:

    • Review and adapt tree planting list (1 year)

    • Identify and preserve best remaining and intact forests (1 year)

    • Create best management practices for use of managing invasive species (1 – 3 years)

    • Outreach targeted to county residents in identification and management of invasive/nonnative species (1 – 3 years)

Climate Change Impacts

For this project, the most important anticipated climate change impacts include:
Temperatures in the Southeast are projected to increase by 4.5 to 8.5 degrees Fahrenheit by 2085
The number of days per year with more than 1 inch of precipitation will increase across the Southeast by the middle of the century
Annual freeze-free season is expected to increase by 20 – 30 days in the Southeast by 2055
Climate change will amplify many existing stressors to forest ecosystems in the Southeast, such as invasive species and insect pests
The urban heat island effect can exacerbate the effects of increasing temperatures
Impervious cover can exacerbate the effects of increased heavy precipitation events in urban areas

Challenges and Opportunities

Climate change will present challenges and opportunities for accomplishing the management objectives of this project, including:

Challenges

Reduced tree species selection of drought intolerant northern species such as northern red oaks, hemlock, American beech, and white pine,
Increases in heavy precipitation events will result in increased soil erosion and nutrient loss.
Soil compaction will increase due to high precipitation events
Stressed trees will be more prone to pests and diseases.
More resources will need to be allocated for tree maintenance and establishment due to greater periods between rain events.
Extended growing season favors invasive species and increases competition with native species.
Herbivory pressure from deer can limit the establishment of planted trees.

Opportunities

Decrease threat from gypsy moth and a reduction in their population. Wetter springs supports a introduced biocontrol fungus, Entomophaga maimaiga. Also, egg masses require cold winters for development. Increase temperatures during the winter could suppres
Increase in palate of southern tree species that can adapt to the area. This could offset the loss of less adaptable northern species.
Warmer winter temperatures could result in decreased use of deicing treatments like road salt, brining, and sand.
Increases in temperature may increase public desire for shade trees to help mitigate heat island effects.
Some native species will benefit from climate change like red cedar, sweet gum, and pawpaw.

Adaptation Actions

Project participants used the Adaptation Workbook to develop several adaptation actions for this project, including:

Area/Topic
Approach
Tactics
County-wide
Promoting and implementation of a natural landscape policy that favors native species
Support conservation, open space easements, and reforestation to reduce forest fragmentation and expand natural corridors.
Strengthen state legislation to promote forest health
Partner with stakeholders to promote urban forestry and tree planting
Staff and volunteer participation in EDRR. Participate in public outreach on the threat from potential future invasive.
Adding organic soil amendments (e.g. mulch and biochar) to urban sites undergoing restoration or revegetation
Restoring or reforesting riparian areas in order to reduce erosion and nutrient loading into adjacent water bodies.
Removing non-native invasive species to reduce competition, and to improve native species diversity
Promoting the conservation of high-quality remnant forest.
Selecting species and cultivars that are less susceptible to pests and pathogens
Treating susceptible trees with pesticides and fungicides when appropriate and feasible.
Encouraging a variety of species from several taxonomic levels that are adapted to wide tolerances rather than just specific current conditions.
Support Fairfax County deer management program and other urban hunting
Continue to monitor canopy use aerial/satellite imagery and LIDAR
Increasing the representation of or incorporating new regionally native or currently southern species in urban planting projects.

Monitoring

Project participants identified several monitoring items that could help inform future management, including:
Existing percent tree canopy coverage
Number of development plans submitted to the County for review
Number of trees planted per year
Quantity of different species planted
Established invasive species

Learn More

To learn more about this project, contact
Leslie
.

Keywords

Invasive species
Planting
Urban

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