CLIMATE AND WILDFIRE IN WESTERN NORTH AMERICA

WESTERLING, A., SWETNAM, T.W., AND CAYAN, D.R.

Documentary and reconstructed fire records from around western North America show associations between fire activity and both concurrent and antecedent climate on seasonal to decadal scales. Interestingly, the strength and lagged timing of these associations varies widely over space in ways that are consistent with hypotheses regarding interdependencies between fire regimes and dominant vegetation types. We present evidence of associations between wildfire and climate as characterized by antecedent moisture anomalies, concurrent drought, spring and summer temperatures, and the timing of the arrival of spring at higher elevations. We present evidence of recent trends in the incidence of large forest fires that appear to be related to trends in temperature, and use statistical reconstructions of fire activity to place these events in a long term context. Using dynamic model reconstructions of soil moisture and remote sensing-based characterizations of biomass changes, we attempt to test some "conventional wisdom" hypotheses regarding the role of vegetation in intermediating between antecedent climate signals that appear to correlate with subsequent fire activity.