controls on fire in the pacific northwest: climate, fuels, and land management dave peterson &...
Post on 21-Dec-2015
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Controls on Fire in the Pacific Northwest: Climate, Fuels, and Land
Management
Dave Peterson & Don McKenzieForest Service – PNW Research Station
Pacific Wildland Fire Sciences LabUW College of Forest Resources
Assumptions about fire and fuels
“Historic data show that wildfires are getting larger and becoming more intense.” – Forest Service Southwest Region web site
Assumption 1: Fires are larger and more intense than earlier in the 20th century
Assumption 2: The size and intensity of wildfires are controlled by fuel accumulations
What causes large and severe fires?
Annual area burned – 11 Western states
1945 decrease Effective suppression?
1975 increase Fuel build-up?
Acr
es b
urn
ed
1945 decrease Effective suppression?
1980 increase Fuel buildup?
Annual area burned – 11 Western states
1945 decrease Effective suppression?
1975 increase Fuel build-up?
Acr
es b
urn
ed
cool warm cool warm cool?
Pacific Decadal Oscillation phase
Years with fire area > 80,000 hectares
National Forest data, 1916-2002
Warm-phase PDO Cool-phase PDO
Idaho 14 7
Oregon 14 5
Washington 10 2
TOTAL 38 (73%) 14 (27%)
Climatology affects wildfire in the Pacific Northwest
Extreme wildfire years are forced at least in part by antecedent drought and summer blocking in the 500-hPa height field.
From Gedalof et al. (2004), Ecological Applications in press
M ay
Septem ber
August
July
June
Limiting factors vary by ecosystem
Fuels
Clim
ate
Boreal Subalpine Lodgepole pine Ponderosa pine (PNW) Calif. mixed conifer Ponderosa pine (SW) Oak woodland Chaparral
Traditional perspective:pyrophobia
Revisionist perspective:pyrophilia
But many are still in denial
Managing fire and fuels is mostly a sociocultural challenge
Federal fire suppression cost in 2002 = $1.6 billion (~$500 per ha burned)
Fuel structures can be complex
Current conditions Target (historical) conditions
Silviculture meets fire science
Scientific principles of fuel treatment:
• Raise canopy base height
• Reduce canopy bulk density
• Reduce canopy continuity
AND reduce surface fuels
Principle #1 – Canopy base height
Dense stand with understory
-------- Canopy base height < 2 m
Treated stand after thinning from below
-------- Canopy base height > 6 m
Principle #2 – Canopy bulk density
Dense stand with understory
Canopy BD > 0.30 kg m-3
Treated stand after thinning from below
Canopy BD < 0.10 kg m-3
Principle #3 – Canopy continuity
Dense stand with understory
Treated stand after thinning from below
Surface fuels must be treated following removal of trees
Analysis of stand development assists treatment scheduling
2005 2010 2015 2020
No treatment
Thinning
Silviculture meets fire science
Many constraints to effective fuel treatments
Need lots of tree removal
Lack of markets for small wood
EIS, EA and other review
Litigation
Risk of escaped fire
Scheduling (~20-year cycle)
A rational approach to fire management and fuel reduction: Focus on the wildland-urban interface
Benefits
Focus fuel treatment area
Protect high economic value
Reduce fire suppression cost
Respond to political concern
Create defensible zones
Reduce liability
Toward science-based firemanagement and policy
Develop guidelines that quantify the effects of fuel treatments on fire behavior
Integrate scientific information and human values(ecological + cultural restoration)
Develop a rational economic approach
Educate the public on living with fire
The restoration pathway will vary