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Implications of climate change on fire and thinning prescriptions
Jessica Halofsky1, 2
Morris Johnson2
1 University of Washington, School of Forest Resources2 U. S. Forest Service, Pacific Wildland Fire Sciences
Laboratory, Seattle, WA
Climate controls ecosystem processes
• The hydrologic cycle
• Plant establishment, growth, and distribution
• Disturbance– Drought– Fire – Flooding– Insect outbreaks
Fire Behavior Triangle
Fuels
Topography Weather
Fire Behavior Triangle
Fuels
Topography Weather
Area burned – Western U.S., 1916 - 2007
Area burned – Western U.S., 1916 - 2007
Fire Suppression Fire Exclusion Fuel Accumulation
Area burned – Western U.S., 1916 - 2007
Fire Suppression Fire Exclusion Fuel Accumulation
Area burned – Western U.S., 1916 - 2007
Fire Suppression Fire Exclusion Fuel Accumulation Lots of Fire Much Less Fire Lots of Fire
Fire area burned and PDO
Cascade Mixed ecoregionCascade Mixed ecoregion
Figure courtesy of J. Littell
Years with fire area > 200,000 acres
Warm-Phase PDO Cool-Phase PDO
Idaho 15 7
Oregon 14 5
Washington 11 2
TOTAL 40 (74%) 14 (26%)
Climate Change and Fire
• Warmer and drier spring conditions =– early snowmelt– lower summer soil and
fuel moisture– longer fire seasons – increased fire
frequency and extent• Fire intensity and severity
may also increase
•Average Area Burned 1970-1979 3,000,000 ac
•Average Area Burned 1980-1989 2,900,000 ac
•Average Area Burned 1990-1999 3,200,000 ac
•Average Area Burned 2000-2007 7,100,000 ac
Trends in Area Burned
• Length of fire season• Fire intensity/severity• Number of fires• Invasive species (cheatgrass)• Time needed to suppress average wildfire• Cost of suppression• Number of structures lost• Strain on fire management resources
Recent trends also show increased:
Analysis of wildfire data since 1916 for the 11 contiguous Western states shows that for a 4°F increase that annual area burned will be 2-3 times higher.
McKenzie et al. (2004), Conservation Biology 18:890-902
How much will area burned increase with climate change?
McKenzie et al. (2004)
Wildfire area burned in Oregon with 2°C warming
McKenzie et al. (2004), Conservation Biology 18:890-902McKenzie et al. (2004)
Wildfire area burned in Washington with 2°C warming
McKenzie et al. (2004), Conservation Biology 18:890-902McKenzie et al. (2004)
Projected changes in area burned in the PNW
Littell et al. 2010
Projected changes in area burned in the PNW
Littell et al. 2010
0.5 M Ac0.8 M Ac
1.1 M Ac
2.0 M Ac
Fire Regimes Vary by Environment
Wet Dry
Warm
Cold
Agee 1993
Gradients of Fire Regime Controls
Adapted from J. Agee
Mixed Severity
Mixed Severity
Low Severity
High Severity
Weather Driven
Fuel Driven
Relative influence of climate and fuels on fire regimes in common western US ecosystems
Fuels
Climate
Boreal
Subalpine
Lodgepole pine
Ponderosa pine (PNW-IM)
Mixed evergreen
Calif. mixed conifer
Ponderosa pine (SW)
Pinyon-juniper
Oak woodland
Sagebrush
Chaparral
PNW-IM = Pacific Northwest and intermountain region of the West SW = American Southwest
Relative influence of climate and fuels on fire regimes in common western US ecosystems
Fuels
Climate
Boreal
Subalpine
Lodgepole pine
Ponderosa pine (PNW-IM)
Mixed evergreen
Calif. mixed conifer
Ponderosa pine (SW)
Pinyon-juniper
Oak woodland
Sagebrush
Chaparral
PNW-IM = Pacific Northwest and intermountain region of the West SW = American Southwest
Relative influence of climate and fuels on fire regimes in common western US ecosystems
Fuels
Climate
Boreal
Subalpine
Lodgepole pine
Ponderosa pine (PNW-IM)
Mixed evergreen
Calif. mixed conifer
Ponderosa pine (SW)
Pinyon-juniper
Oak woodland
Sagebrush
Chaparral
PNW-IM = Pacific Northwest and intermountain region of the West SW = American Southwest
Climate Change
Some energy (climate) limited forests may become water (fuel) limited forests
Littell et al. 2010
Variation in Fire Severity within a General Fire RegimePr
opor
tion
SeverityAdapted from Agee 1993
Low
Moderate
High
Low Mixed High
Initially, with more frequent extreme burning conditions?Pr
opor
tion
Low Mixed HighSeverity
Adapted from Agee 1993
Low
High
Moderate
With eventual drought- and fire-induced reductions in fuel in drier forest types?
Prop
ortio
n
SeverityAdapted from Agee 1993
Low High
Low Mixed High
Moderate
Fire Regimes and Landscape Patterns
Agee 1998
Low-Severity Fire Regime
Mixed-Severity Fire Regime
High-Severity Fire Regime
MIR
OC3
_MED
RES A2 A1B B1
HAD
CM3
CSIR
O_M
K3
percent
Percent change in biomass consumed by fire2051-2100 vs. 1951-2000
R. Neilson et al., USFS and OSU MAPSS Team, Corvallis, OR
Fire interacts with other disturbances and
vegetation/fuel conditions
The Disease Spiral
Manion 1991
McKenzie et al. 2009
Adaptation strategies for natural resource management?
Adaptation strategy #1Increase landscape diversity
Thin forest stands to create lower density, and diverse stand structures and species assemblages that reduce fire hazard and increase resilience to wildfire.
Adaptation strategy #2Increase resilience at large spatial
scales
Implement thinning and surface fuel treatments across large portions of landscapes where wildfires may occur
Orient the location of treatments to modify fire severity and fire spread
Focus the spatial scale of treatments on units of hundreds to thousands of acres
Adaptation strategy #3Maintain biological diversity
Modify genetic guidelines
Experiment with mixed species, mixed genotypes
Assist colonization, establish neo-native species
Identify species, populations, and communities that are sensitive to increased disturbance
Adaptation strategy #4Plan for post-disturbance management
Treat fire and other ecological disturbance as normal, periodic occurrences
Incorporate fire management options directly in general planning process
Adaptation strategy #5Implement early detection / rapid response
Eliminate or control exotic species
Monitor post-disturbance conditions, reduce fire-enhancing species (e.g., cheatgrass)
Adaptation strategy #6Collaborate with a variety of partners
Develop mutual plans for fire and fuels management with adjacent landowners to ensure consistency and effectiveness across large landscapes
Adaptation strategy #7Promote education and awareness about climate change
Facilitate discussion among management staff regarding the effects of a warmer climate on fire and interactions among multiple resources
Educate local residents about how a warmer climate will increase fire frequency and how fuel reduction can protect property