ECOLOGICAL CONTEXT OF CLIMATE IMPACTS ON FIRE: WILDLAND FIRE AREA
BURNED IN THE WESTERN U.S. 1916-2003
LITTELL, JEREMY S. (1, 2); MCKENZIE, DONALD (3); PETERSON, DAVID L. (1,2,3)
(1) Fire and Mountain Ecology Lab, University of Washington College of Forest Resources,
Seattle, WA, (2) JISAO CSES Climate Impacts Group, Seattle, WA, (3) Fire and Environmental
Research Applications Team, USDA Forest Service PNW Research Station, Seattle, WA
We used two wildland fire area burned datasets and historical climate data to evaluate the degree
to which climate variability between 1916 and 2003 exerted an influence on the annual area
burned in eco-provinces of 11 western states in the US. One of the fire datasets is 88 yr long and
cumulated by state. The second is 21 yr but has greater spatial precision at 1°x 1° lat/long. We
used the relationships during the common period to reconstruct area burned by eco-province for
the full record. Preliminary work suggests relationships between the two fire area burned datasets
are reasonable for reconstruction purposes in most eco-provinces (average R^2 = 0.55, range =
0.16 – 0.81) and that the fire/climate relationships are often temperature- and drought- driven.
Sub-regional seasonal and annual predictors for temperature and precipitation combined explain
25-52% (mean 30%) of the variability in 1916-2003 fire area burned. Increasing fire area is
positively associated with lagged precipitation for many of the semi-desert steppe and grassland
eco-provinces, whereas the relationship is negative for more heavily forested eco-provinces.
Annual temperature, however, is the single best predictor for 9 of the 15 preliminary eco-province
models. Our results suggest that the ecological context of twentieth century climate/fire
relationships has some similar features with the fire history record prior to the mid-19th century.