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Natural Disturbance and Environmental Assessments in the Oil Sands Region

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Natural Disturbance and Environmental Assessments in the Oil Sands Region. Linda Halsey April 2012. Why Include Natural Disturbance in Assessments??. Driver = JRP Decision Report for the Joslyn North Mine (Jan 2011)

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Why Include Natural Disturbance in Assessments??

  • Driver = JRP Decision Report for the Joslyn North Mine (Jan 2011)
  • JRP considered it a best practice for understanding cumulative effects would include future fire in the assessment of change to terrestrial habitat and wildlife
  • Future fire modeling not included in EIAs to any extent prior to JRP Decision Report


  • Temporal Considerations
  • Methods
    • - Assumptions
    • - Spatial inclusion of natural disturbance in assessment
    • - Aspatial inclusion of natural disturbance to generate range of natural variability
  • Results
  • Conclusions

Temporal Considerations

  • Previous EIAs in the oil sands assumed static conditions to forest structure/age class
  • Inclusion of future fire requires the recognition that forest structure/age class is dynamic
    • Forest ages
    • Fire results in stand replacement
  • Proper and consistent use of temporal components critical to the assessment

Temporal Considerations

  • Reference Condition
    • benchmark(s) for comparison purposes
  • Case
    • assemblage of developments and activities
  • Snapshot
    • point in time often defined by a specific Project milestone

Temporal Considerations

Clearing begins

Production Begins

Stream Diversion

Maximum Build-Out


Planned Development Case

Application Case

Base Case


Baseline Condition

Predevelopment Condition



Temporal Considerations

  • Predevelopment Conditions (No Anthropogenic Disturbance)
    • Must include future forest fire to allow for true comparison of development effects
  • Existing Conditions (Baseline)
    • Does not include future forest fire

Temporal Considerations

  • Predevelopment conditions were generated from 2008 data by assigning vegetation types to all disturbances on the landscape
  • For temporal consistency with assessment cases predevelopment vegetation was aged to the appropriate snapshot (i.e., stands were grown to reflect the 2057 maximum build-out snapshot) and natural disturbance (i.e., fire) was added and forest age “reset” to 0 Years
  • Existing conditions are at 2008 (not temporally consistent with predevelopment and assessment cases)
  • Assessment completed relative to predevelopment not existing conditions

Methods - Assumptions

  • 80 year fire cycle (i.e., 1/80th of the study area burns each year)
  • Fire size followed a log normal distribution (many small fires and few large fires)
  • Forested vegetation cover classes all had an equivalent potential to burn (circular fires applied, fires can overlap)
  • Ecosystem succession not considered (cover classes static with only structural stage changing for forested cover classes)

Methods – Spatial Application

  • 100 spatial runs completed on the predevelopment landscape (i.e., no disturbance) with future fire applied following the stated assumptions to the Project snapshot chosen for assessment (i.e., maximum build-out 2057)
  • For areas where fire occurred forest age class was reset to zero and then progressively aged. For areas where fire did not occur, forest age class was advanced
  • Mean forest age of each spatial run determined for the study area

Methods – Spatial Application

  • Spatial run closest to average mean age of all 100 spatial runs used in assessment
  • Developments than applied to that average mean age predevelopment landscape by case


Base Case

Application Case


Methods – Aspatial Application (RNV)

  • Generated RNV for forested cover classes by considering only natural disturbance (i.e., fire)
  • Twenty runs completed using a Monte Carlo simuation for a 300-year period with the first 100 years being discarded to ensure decoupling from existing conditions

Methods – Aspatial Application (RNV)

  • Average age for forested cover class (weighted by landscape distribution) and the upper and lower 95% confidence limits of age were determined
  • Spatial representation of RNV was generated for the upper and lower 95% confidence limits using the 100 natural disturbance simulations
  • RNV used in effects classification




Case “A” inside RNV


Case “B” outside RNV


Methods – Additional Considerations

  • Inclusion of timber harvesting for full life of Project
  • Inclusion of progressive reclamation for regional developments


  • Examples of wildlife habitat responses to future fire modeling for several Species at Risk:
    • Canada warbler (species that prefer older more structurally complex areas)
    • Wood bison (species that prefer younger more open areas)
    • Western toad (species that prefers open wetlands)

Results – Canada Warbler

  • Mixedwood vegetation types that are dominated by deciduous tree species with a tall (2.5 m to 3.5m), thick shrubby understory composed of deciduous shrub species are preferred
  • Mature tree stands (structural stages 6 and 7) or greater than 120 years old are preferred because of higher abundance of understory as are moist riparian areas and moist woodlands
  • Different disturbance types lower habitat suitability rankingswithin 150 to 300 m of the disturbance

Results – Canada Warbler

  • High and moderate habitat availability consistently drops as development increases
  • Range of natural variability at 5% confidence interval has an area of 129,540 ha or -23.9% of predevelopment

Results – Wood Bison

  • High and moderate habitat suitability for wood bison represented generally by younger forests, shrublands and grasslands/wetlands that support grasses and sedges
  • Different disturbance types lower habitat suitability rankings within 100 to 200 m of the disturbance

Results – Wood Bison

-13.2% change

-1.8% change

-33.6% change

  • Habitat availability declines as expected with increasing development
  • RNV not considered as aspatial simulations resulted in an average forest age for relevant cover classes that was illogical (i.e., function of snapshot not being decoupled from existing conditions)
  • Existing conditions have less high and moderate habitat availability than the assessment cases due to:
    • Simulated future fires for predevelopment and assessment cases resulting in younger structural stages being present
    • Inclusion of progressive reclamation and young forests for cases
    • Decrease in fragmentation and Zones of Influence with addition of mines for cases

Results – Western Toad

  • All standing and flowing water cover classes (excluding the Athabasca River), including open fen and marsh vegetation cover class polygons, were assumed to offer suitable breeding habitat and are therefore given high ratings.
  • Vegetation cover classes with adequate moisture and high ground and shrub cover were assumed to provide suitable terrestrial habitat.
  • Cover classes within 1000 m of breeding habitat had increased habitat suitability
  • Different disturbance types lower habitat suitability rankings within 50 to 400 m of the disturbance

Results – Western Toad

  • Slight increase between existing conditions and base case reflects progressive reclamation and increase in areas of open water
  • No change in habitat rankings associated with fire as open and shrubby wetlands static (i.e., range of natural variability not included)


  • Frontier Oil Sands Mine first assessment to include natural disturbance as part of cumulative effects assessment for terrestrial habitat and wildlife species
  • Clear need to ensure proper use of temporal conditions
  • Old growth dependent species results are logical
  • Young forest dependent species results not inherently logical
  • Limitations:
    • Only of relevance to species that have a high dependency on habitat types related to forest age class
    • Spatial inclusion of fire highly dependent on existing conditions and length of snapshot time
  • Acknowledgements: Teck Resources Limited, Owner and Applicant of the Frontier Oil Sands Mine Project