Fairfax County’s Tree Canopy: Examining the Effects of Land Development Regulations on Tree Canopy Conservation Eric Wiseman, PhD Associate Professor of Urban & Community Forestry Dept. of Forest Resources & Environmental Conservation Virginia Tech [email protected] Brian Keightley Director of Urban Forest Management Division Dept. of Public Works & Environmental Services Fairfax County, Virginia [email protected]
E. Wiseman & B. Keightley 02 • 32 Acknowledgements Casey Trees • Mark Buscaino • Andrew Schichtel Fairfax County • Todd Nelson • Rachel Habig-Myers PlanIT Geo • Ian Hanou • Andy Evans • Michaila Musman • Brett Martin • Ben Wittman Virginia Tech • Meghan Failor • J. P. Gannon • Claire White
E. Wiseman & B. Keightley 03 • 32 Presentation Overview • Background on Fairfax County urban forest management and policies • Findings of Fairfax County tree canopy cover research conducted by Virginia Tech • Future implications of research findings for tree canopy conservation in Fairfax County Source: www.fairfaxcountyeda.org Purpose: Show how Fairfax County is using science to understand its policies and inform tree canopy conservation
E. Wiseman & B. Keightley 04 • 32 Background and Context Census Facts About Fairfax County 391.0 square miles of land area and is the 47th largest county in VA by total area Source: data.census.gov/profile/Fairfax_County,_Virginia?g=050XX00US51059 • Most populated county in VA • Most populated jurisdiction in D.C. metro area
E. Wiseman & B. Keightley 05 • 32 Background and Context • 1973: County’s tree preservation and planting requirements were originally adopted. Office of the County Arborist established. • 1989: County enacted VA Code 15.2-961. Replacement of trees during development process in certain localities. • 2008: County enacted VA Code 15.2-961.1. Conservation of trees during land development process in localities belonging to a nonattainment area for air quality standards. Trees and Development in Fairfax County Source: Brian Keightley
E. Wiseman & B. Keightley 06 • 32 Background and Context • 2016: Tree Planting and Preservation Fund distribution policy is approved. • 2020: Tree Action Plan authored by Tree Commission is approved. No net loss of tree canopy. • 2022: Community Tree Canopy goals set in CECAP plan. • 2023: County approves Tree Planting and Preservation Fund grant to Casey Trees to perform tree canopy study. • 2023: Forest Conservation Branch is moved from Urban Forest Mgt. to Land Development Services. Trees and Development in Fairfax County Source: Brian Keightley
E. Wiseman & B. Keightley 08 • 32 Background and Context Source: Fairfax County Land Development Services Annual Report 2023 Ten-Year Land Development Trend in Fairfax County Source: Brian Keightley Source: Brian Keightley
E. Wiseman & B. Keightley 09 • 32 Background and Context Imagery Year Source of Data/Analysis Imagery Resolution Tree Canopy Cover (%) 2005 US Forest Service 30 meter 42%* 2011 Univ. Vermont/Casey Trees 1 meter 53% 2014 Ches. Conservancy/Casey Trees 1 meter 53.9% 2015 Univ. Vermont/Casey Trees 1 meter 57% 2018 Ches. Conservancy/Casey Trees 0.6 meter 53.6% 2018 Ches. Bay Prog./UVM/US Forest Service 0.6 meter 55.4% 2012 USDA NAIP/Casey Trees/PlanIT Geo 1 meter 52% 2021 USDA NAIP/Casey Trees/PlanIT Geo 0.6 meter 55% Land Cover and Tree Canopy Studies
E. Wiseman & B. Keightley 10 • 32 Background and Context How does Fairfax County know if approved development plans are meeting 10-year canopy requirement? Land Cover and Tree Canopy Studies Source: Brian Keightley
E. Wiseman & B. Keightley Research Scope and Aim 11 • 32 Main Research Question What are patterns and trends in parcel-level tree canopy cover for properties developed since passage of the tree canopy conservation ordinance in 2009? Conceptual Framework for Research Questions Ordinance Sets The Tree Canopy Cover Requirement Tree Canopy Target Is Proposed in the Site Plan Trees Are Preserved and Planted at Development Tree Canopy Cover Is Measured 10 years Post-Development Source: www.ffxnow.com/2022/03/09
E. Wiseman & B. Keightley Research Methods 13 • 32 Tree Canopy Target Is Proposed in the Site Plan 1. Existing Canopy: 26% 2. Required Canopy: 30% 6. Total Proposed Canopy: 32.5% 5. Planted Canopy: 0% 3. Preserved Canopy: 26% 4. Preservation Multiplier (1.25 x): 32.5%
E. Wiseman & B. Keightley Research Methods 14 • 32 Tree Canopy Cover Is Measured 10 years Post-Development Parcel Land Area 0.60 ac Parcel Tree Canopy Area 0.36 ac Tree Canopy Cover % 60% Source: 2021 PlanIt Geo Tree Canopy Assessment 60% County Parcel GIS Layer Overlay on 0.6 m resolution NAIP PlanIT Geo Canopy Measurement Overlay on Parcel GIS Layer Example Data Point
E. Wiseman & B. Keightley Research Methods 15 • 32 Land Development Data Sets Are Compiled and Analyzed 2021 GIS Parcel Data 2021 Tree Canopy Data 2009-2021 Site Plans Study Population: All Parcels developed 2009 – 2021 N = 7,162 Study Sub-Population: All parcels developed 2009 – 2011 N = 482 Site Plan Sample: Residential infill parcels developed 2009 – 2011 n = 151
E. Wiseman & B. Keightley Research Findings 16 • 32 What Percentage of Parcels Met Their Tree Canopy Requirements? Overall: Yes: 383 (80%) No: 99 (20%) Zone Type Effect: p=0.065 All land parcels developed from 2009 to 2011 (N=482)
E. Wiseman & B. Keightley Research Findings 17 • 32 How Much Did the Measured Canopy Differ From the Required Canopy on Parcels? All land parcels developed from 2009 to 2011 (N=482) Avg. Diff. 16% (p<0.01) Avg. Diff. 11% (Not significant) Avg. Diff. 7% (Insufficient sample) Avg. Diff. 8% (Insufficient sample) All Zone Types: Avg. Diff. 16% (p<0.01) Zone Type Effect: p=0.116
E. Wiseman & B. Keightley Research Findings 18 • 32 Did Development Plan Type Influence Meeting The Canopy Requirement? All land parcels developed from 2009 to 2011 (N=482) Diff. 7.9% (Insufficient sample) Avg. Diff. 17.6% (Not significant) Avg. Diff. 15.7% (p<0.05) All Plan Types: Avg. Diff. 15.8% (p<0.01) Plan Type Effect: p=0.992
E. Wiseman & B. Keightley Research Findings 19 • 32 What Differences Were There Between Parcels That Did and Didn’t Meet Requirements? Residential infill parcels developed from 2009 to 2011 (N=424) Parcels Not Meeting Requirement Were… Smaller More Intensively Developed Had Slightly Smaller Canopy Requirement Had Much Less Measured Canopy
E. Wiseman & B. Keightley Research Findings 20 • 32 Did Residential Zone Code Have Any Influence on Meeting Canopy Requirements? Sample of residential infill parcels developed from 2009 to 2011 (n=151) Overall: Yes: 123 (81%) No: 28 (19%) Zone Code Effect: p=0.371 33.3% 50.4%
E. Wiseman & B. Keightley Research Findings 22 • 32 Are Developers Hitting Their Target For Proposed Tree Canopy? Sample of residential infill parcels developed from 2009 to 2011 (n=151) Tree canopy requirements were similar Proposed canopy targets exceeded requirements for both The ‘non-compliers’ really under-achieved The ‘compliers’ may offset the ‘non-compliers’ Comparing those that did and did not comply… ‘Compliers’ had larger parcels ‘Compliers’ had less impervious surface
E. Wiseman & B. Keightley Research Implications and Future Work 23 • 32 • Most effective tool to maintain regional canopy • “Seed trees” for the next generation of forest • Preserved trees drive significant canopy growth • Preserved trees reduce the heat island effect • Preserved trees enhance property value • Preserved trees maintain watershed function • Soil stabilization • Intercepting precipitation • Ecosystem services of aquatic habitat Tree Conservation During Land Development Source: Brian Keightley
E. Wiseman & B. Keightley Research Implications and Future Work 24 • 32 The Dillon Rule is the principal that local government only exercises: 1. Powers expressly granted by the state 2. Powers necessarily and fairly implied from the grant of power 3. Powers crucial to the existence of local government Policy Challenges of the Dillon Rule Source: commons.m.wikimedia.org
E. Wiseman & B. Keightley Research Implications and Future Work 25 • 32 • Credits for planting trees • Standards for preserved trees What Policies Might Fairfax County Consider Changing? • Changes to development approval processes • Standardize developer tree canopy calculations Source: Brian Keightley
E. Wiseman & B. Keightley Research Implications and Future Work 26 • 32 • Tree canopy requirement per zoning district • Tree planting and preservation multipliers (i.e. “tree canopy bonus”) • Tree planting fund conditions and criteria • Areas affected by § 15.2-961.1 • Currently limited to Planning District 8 • Professionals who can endorse tree preservation plans Possible Changes to VA Code § 15.2-961.1 Source: www.vapdc.org/pdc-map Source: en.wikipedia.org/wiki/Virginia_State_Capitol
E. Wiseman & B. Keightley Research Implications and Future Work 27 • 32 MWCOG Generalized Zoning MWCOG Regional Tree Canopy Goal § 15.2-961.1 Canopy Requirements 2021 Fairfax County Tree Canopy Result* Low-Density Residential 55% 30% 56.1% Medium-Density Residential 50% 25% 46.5% High-Density Residential 35% 20% 37.4% Urban High-Density Residential 25% 15% 28.2% Commercial 25-35% 10% 15.6% Industrial 30% 10% 31.9% *VA Code § 15.2-961.1 and Fairfax County zoning districts do not align exactly to MWCOG generalized zoning categories used for canopy goal setting Working Towards Regional Tree Canopy Goals Source: CONSERVING TREES AND FORESTS IN METROPOLITAN WASHINGTON Prepared by the COG Regional Tree Canopy Subcommittee for the COG Climate, Energy, and Environment Policy Committee Publish date: April 10, 2024 www.mwcog.org/documents/2024/04/10/conserving-trees-and-forests-in-metropolitan-washington-climate--energy-tree-canopy
E. Wiseman & B. Keightley Research Implications and Future Work 28 • 32 Working Towards Fairfax County’s Tree Canopy Goals Goal: Achieve 60% tree canopy with at least 40% coverage in every census block by 2030 and 50% by 2050, prioritizing areas of highest socioeconomic need
E. Wiseman & B. Keightley Research Implications and Future Work 29 • 32 Working Towards Fairfax County’s Tree Canopy Goals Goal: Achieve 60% tree canopy with at least 40% coverage in every census block by 2030 and 50% by 2050, prioritizing areas of highest socioeconomic need
E. Wiseman & B. Keightley Presentation Takeaways 31 • 32 • Tree conservation is the most effective tool to maintain canopy levels • While there is room to improve, VA Code §15.2-961.1 has yielded positive results • Tree canopy growth is incremental and occurs at the margins • Scale of tree planting needed to increase canopy is substantial • Fairfax County hopes to work with Virginia Tech to refine research methodologies • Fairfax County and Virginia should continue to base their tree conservation policies on the best available scientific data Source: www.fairfaxcounty.gov/publicworks/trees/treecommission
Tree Canopy: Examining the Effects of Land Development Regulations on Tree Canopy Conservation Eric Wiseman, PhD Associate Professor of Urban & Community Forestry Dept. of Forest Resources & Environmental Conservation Virginia Tech [email protected] Brian Keightley Director of Urban Forest Management Division Dept. of Public Works & Environmental Services Fairfax County, Virginia [email protected] 32 • 32
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