PRELIMINARY RESULTS – DO NOT CITE Ecosystem Controls on the Relationship between Climate Variability and 20th Century Fire in the American West Jeremy Littell UW College of Forest Resources Climate Impacts Group PRELIMINARY RESULTS – DO NOT CITE

Area Burned in the Western U.S. More area burned does not necessarily equate to more ecological impact. More area burned DOES equate to more money spent fighting fires and more air pollution. Area burned is a metric used to effect change on everything from ecosystem management to EPA air quality standards.

PRELIMINARY RESULTS – DO NOT CITE Reported Area Burned Fire Suppression  Fire Exclusion  “Catastrophic” Fires Some Fire  Much less fire  A lot of fire Cool PDOWarm PDO

PRELIMINARY RESULTS – DO NOT CITE Recent Climate / Fire Work Long-term (1916), coarse scale, seasonal relationships Short-term (1980), fine- scale, monthly climate and synoptic relationships Short-term, coarse scale ecological relationships No long-term, modern, ecologically specific work McKenzie et al Conservation Biology Westerling et al BAMS.

PRELIMINARY RESULTS – DO NOT CITE Climate Drivers of Fire Area Burned Increasing temperature (winter and summer) appears related to increasing area burned trend. Inter-annual wet/drought “cycles” also appear related to small/big fire years. Combination of long-term soil  fuel moisture (“set-up”) and short term weather (sub-seasonal blocking ridges and storm fronts) implicated

PRELIMINARY RESULTS – DO NOT CITE Objectives Derive a set of more ecologically-relevant time series of wildland fire area burned. Relate these to 20 th century seasonal climate. Evaluate ecological underpinnings of strongest relationships.

PRELIMINARY RESULTS – DO NOT CITE Objectives Derive a set of more ecologically- relevant time series of wildland fire area burned. Relate reconstructions to 20 th century seasonal climate. Evaluate ecological underpinnings of strongest relationships.

PRELIMINARY RESULTS – DO NOT CITE Reconstructing Area Burned State Data: Gridded Data:

PRELIMINARY RESULTS – DO NOT CITE Caveats Is the state-level data correctly normalized for reporting area in the early 20 th century? Is the proportion of area burned attributable to climate (vs. land use, vegetation dynamics, or fire exclusion) reasonably stationary? NO! ?????

PRELIMINARY RESULTS – DO NOT CITE Area Reporting Between 1916 and 1964, most states contained between 10% and 60% of the public land they do today Acres in 1916  Acres in 2002, so each state series adjusted by smoothed area reporting

PRELIMINARY RESULTS – DO NOT CITE Reconstructing Area Burned Area burned time series almost never have any significant autocorrelation Noisy, non-normal data Several orders of magnitude in observations

PRELIMINARY RESULTS – DO NOT CITE Useful Distributions for Modeling Fire Most Gridded, State, and Eco-province data are log- normal, but the log of the variance is proportional to the mean squared.

PRELIMINARY RESULTS – DO NOT CITE Reconstructing Eco-province Area Burned from State and Grid Data Regression models, training period is : Log models: ln (Cascade Mixed (gridcells))= ln (WA) + ln(OR) + ln(WA):ln(OR) Gamma models: Cascade Mixed = WA + OR + WA:OR | σ ~ μ 2 Use modeled relationship for best model to backcast Cascade Mixed for full dataset.

PRELIMINARY RESULTS – DO NOT CITE Ecoprovince Reconstruction Results

PRELIMINARY RESULTS – DO NOT CITE Reconstructing Area Burned Area Burned (ac x 10 6 )

PRELIMINARY RESULTS – DO NOT CITE Objectives Derive a set of more ecologically-relevant time series of wildland fire area burned. Relate reconstructions to 20 th century seasonal climate. Evaluate ecological underpinnings of strongest relationships.

PRELIMINARY RESULTS – DO NOT CITE Developing Seasonal Ecoprovince Climate Several constituent HCN divisions for most provinces Standardized, area- weighted, pre- whitened time series of T, PPT, PDSI: –Annual (Oct. - Sep.) –Winter (NDJFM) –Spring (MAM) –Summer (JJA) – GS (MJJAS) Ecoprovince T, PPT, PDSI Climate Time Series

PRELIMINARY RESULTS – DO NOT CITE Climate – Fire Relationships: Summary Reconstructed and observed fire area burned relationships with climate similar in magnitude and seasonal pattern Year of fire summer precipitation, temperature significant in most ecoprovinces Broad, regional patterns in climate/fire correlations emerge

PRELIMINARY RESULTS – DO NOT CITE Southwest Regional Pattern Four southwest eco- provinces with similar climate correlations + Summer / GS T - Summer / GS PPT + lag 1 Winter / Spring PPT AM.Des (orange) has Annual relationships for same variables

PRELIMINARY RESULTS – DO NOT CITE Northern Mountain Ecosystem Pattern Four mountain, forested eco-provinces with similar climate correlations - All Seasons PPT + Summer / GS T Year of fire relationships very strong Lag 1 relationships weak, but same sign

PRELIMINARY RESULTS – DO NOT CITE Southern Mountain Ecosystem Pattern Three mountain, mixed eco-provinces with similar climate correlations + Summer / GS T - Summer / GS PPT Lag 1 relationships mixed; some like desert SW, others like northern Mountains

PRELIMINARY RESULTS – DO NOT CITE Mixed Dry Ecosystem Pattern Three dry eco-provinces with similar climate correlations Strong Year-of, - PDSI Lag 1 relationships mixed –T and +PPT, PDSI

PRELIMINARY RESULTS – DO NOT CITE Objectives Derive a set of more ecologically-relevant time series of wildland fire area burned. Relate reconstructions to 20 th century seasonal climate. Evaluate ecological underpinnings of strongest relationships.

PRELIMINARY RESULTS – DO NOT CITE Fuels and Ecosystem Pattern Different fuel types respond differently to climate Two mechanisms: drying of fuels and production of fuels Fuel - limited systems Climate - limited systems Ignition - limited systems

PRELIMINARY RESULTS – DO NOT CITE Climate and Fire Correlations not as strong for full period Pattern is ecosystem dependent 21 yr. Moving Correlations show why

PRELIMINARY RESULTS – DO NOT CITE Conclusions Late 20 th century area burned is not unprecedented. Much (between 30% and 70%) of the decrease-increase pattern is related to climate. Ecosystem – specific models are useful for determining the climatic mechanism(s) responsible for fire area burned

PRELIMINARY RESULTS – DO NOT CITE Prospectus Use ecoprovince-specific fire ~ climate models to forecast future area burned given projected climate. Develop Pacific Basin  Climate + Weather  fire process models

PRELIMINARY RESULTS – DO NOT CITE Acknowledgements Tony Westerling Don McKenzie Dave Peterson Phil Mote Tom Swetnam