New York City Case Study: Methods of Analysis

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New York City Case StudyMethods of Analysis

• David J. Nowak
• USDA Forest Service
• Northeastern Research Station
• Syracuse, NY

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New York City Study

• Goal investigate the effects of increased urban
  vegetation on biogenic emissions and pollutant
  concentrations in the New York City area for
  potential incorporation in State Implementation
  Plans

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New York City Project 2001-2002

• What is tree cover in NYC domain area?
• What is reasonable cover increase?
• Could a realistic increase in tree cover have an
  impact on ozone?

Cooperative project with NYS DEC and Davey
Resource Group
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New York City Analysis

• Analyzed aerial photographs to determine space
  available for new tree cover
• Used digital ortho-quad photographs in
  conjunction with MRLC land cover maps
• Modeled three scenarios
• Base case (No change to the 975 urban land use
  grid cells)
• Realistic urban tree cover increase Convert 30
  of the urban grass cover to urban trees
• Maximum urban tree cover increase Convert all
  of the urban grass cover to urban trees

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Tree Cover Increase

• Realistic based on discussion with NYS DEC
  State Forester on reasonable amount of tree cover
  that could be increased (10 increase in tree
  cover in urban areas approximately 500 km2)
• Maximum fill all urban grass areas with trees
  (32 increase in tree cover in urban areas
  approximately 1,600 km2)

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Modeling System

• Meteorology MM5 (Version 3.4), modified to
  accommodate 3 urban land use categories
• Anthropogenic emissions EMS-95
• Biogenic emissions SMOKE-BEIS2
• Photochemistry MODELS-3/CMAQ
• 4 km horizontal grid size
• July 12-15, 1995

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Land Surface Parameterizations (MM5)
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Change in Urban Tree Cover
T, G, I - percent tree, grass, and impervious
cover, respectively
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Biogenic Emissions

• Emissions changed only a few percent

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Biogenic Emission

• Except for isoprene, anthropogenic emissions are
  comparable to or much larger than biogenic
  emissions

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Pollution Removal

• Estimated pollution removal (UFORE model) for
  realistic tree cover increase 500 km2 of new
  cover 1994 data

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Domain max. O3 concentration dropped 4.1 ppb
1 hr ozone - Maximum Cover
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Domain max. O3 concentration dropped 4.4 ppb
1 hr Ozone Realistic Cover
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Domain max. O3 concentration dropped 0.8 ppb
8 hr Ozone - Maximum Cover
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Domain max. O3 concentration dropped 1.0 ppb
8 hr ozone Realistic Cover
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New York City Area Summary

• 10 increase in urban tree cover
• Reduced 1-hour maximum O3 by 4 ppb (132 ppb to
  128 ppb)
• 8-hour maximum O3 by 1 ppb
• Some increases in O3 in the domain
• Little difference in maximum reductions between
  10 and 30 tree cover increase
• Very significant impact
• 3 reduction in peak ozone levels
• 37 reduction in amount needed to gain attainment
• Effects of changes in biogenic emissions were
  minimal, but there is a potential for a slight
  increase
• Additional tree cover will remove thousands of
  tons of air pollutants per year

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Tree Cover Change

• CT CB CN CG CM
• CT total canopy cover in model domain in year n
• CB existing tree cover in base year
• CN canopy increase from new tree planting
• CG growth of existing canopy
• CM canopy mortality or loss due to natural of
  human-induced causes

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Potential Program Options

• Tree planting (?CN)
• Maintenance to promote growth of existing
  canopies (?CG)
• Protect existing canopy (?CM)
• e.g., ordinances
• Education programs (?CN ?CG ?CM)
• Public relation campaigns (?CN ?CG ?CM)

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Increasing in Tree Cover

• Proposed a series of general programs
• CN Canopy increase from planting
• 1 million trees per year for 10 years
• Mortality rate has a dramatic effect
• May take 30 years to reach cover goals
• Cg and Cm
• Preservation, protection, ordinances, maintenance
  and education

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Incorporating Urban Vegetation within SIPs

• Resource assessment
• Modeling the effect of increasing canopy cover on
  ozone
• Developing reasonable management programs that
  could be used to achieve modeled changes in
  canopy cover
• Incorporating the modeling results and management
  programs within a SIP

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1) Resource Assessment

• Establish baseline
• Satellite analyses
• Photo interpretation
• Ground assessments (leaf biomass by species)
• Space available to plant trees

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2) Model Tree Effects

• Work with local air quality modelers
• Base case vs. future case (change tree cover)
• 4 model analyses
• Meteorological effects (MM5)
• Anthropogenic emission effects (e.g., EMS-95)
• Biogenic emission effects (BEIS)
• Integrated model (CAMx), include deposition
  change and other model results

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3) Develop Tree Program

• Work with state and local forestry personnel
• Determine from baseline assessment, reasonable
  amount that tree cover can be increased
• Determine programs that can be implemented to
  reach goal
• Tree planting
• Canopy preservation
• Elimination of mowing (natural regeneration)
• Education and public relations

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Tree Plan Enforcement and Verification

• Determine how program will be verified to ensure
  and verify that it is successful
• Must verify that program worked, not that ozone
  was reduced
• Monitor trees / tree cover vs.
• Monitor programs

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Tree Cover Verification Options

• Remote Sensing
• Program Verification
• Ground Truth (counting trees)

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4) Incorporate Results in SIP

• Work with state officials to incorporate results
  in SIP
• Option
• Flexible SIP Approval Policy for Nontraditional
  Measures currently being developed by EPA
• actions which are voluntary in nature or which
  have not previously been approved into SIPs
  because the actions cannot be quantified as
  accurately as traditional SIP measures due to
  scientific or technical issues
• allows credit to be generated up front

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Flexible SIP Approval

• develop a protocol, based on best available
  science, to quantify emission or pollutant
  reductions for the nontraditional emission
  reduction program
• run the program for a period of time and then
  evaluate the results
• compare the results with the estimated credit and
  make up any shortfall, if one is found

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Issues Remaining

• Emissions reductions
• But trees emit VOC / NOx equivalents
• Land Use Change (bigger issue than trees)
• Models currently assume no change
• Canopy preservation
• Monitoring / verification / enforcement
• Programs vs. tree cover
• Ozone Guidance Document on Mitigation Measures
  (?)

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Conclusion

• Increased tree cover will likely lead to ozone
  reductions
• There are methods available to incorporate
  results into SIPs, but issues remain
• State Forestry and Air Quality personnel need to
  work together to address this issues