Controls on Fire in the Pacific Northwest: Climate, Fuels, and Land Management Dave Peterson & Don McKenzie Forest Service – PNW Research Station Pacific Wildland Fire Sciences Lab UW 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? Acres burned 1945 decrease  Effective suppression?  1980 increase Fuel buildup?

Annual area burned – 11 Western states 1945 decrease  Effective suppression?  1975 increase Fuel build-up? Acres burned cool warm cool warm cool? Pacific Decadal Oscillation phase

Years with fire area > 80,000 hectares National Forest data, 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

Limiting factors vary by ecosystem Fuels Climate 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 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 fire management 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