Tundra fire regimes and responses to climate change: Novel disturbance in the Arctic?

Background/Question/Methods

Anthropogenic climate change may result in novel disturbances in Arctic tundra ecosystems. The frequency and extent of tundra fires in recent years appear striking in some areas of the Arctic. These recent fires may be an early indication that the disturbance regime of tundra ecosystems will differ greatly from today if the trend of Arctic climate warming continues. Are these recent tundra fires unprecedented?  Or do tundra fires occur naturally but infrequently, with observational and satellite records too brief to capture the true natural range of variability?  How is tundra-fire occurrence related to climate conditions?  What are some of the ecological and ecosystem-management implications of tundra burning?  Recent fire events in tundra ecosystems have motivated scientists to address these questions.  This presentation highlights some of the recent findings about tundra-fire regimes.  We aim to (1) provide a long-term context for recent tundra burning using historical and paleofire records; (2) elucidate how tundra area burned is related to climatic variability over the past 60 years, and apply these relationships to estimate annual tundra burning over the 21^st century; (3) describe the impacts of tundra burning on biogeochemical and biophysical processes; and (4) discuss the management implications of increased tundra burning in the Arctic.

Results/Conclusions

Historical and paleofire data show that Arctic tundra can sustain an extremely wide range of fire regimes, with individual fire return intervals spanning several orders of magnitude.  These data imply that what historically appears to be a non-flammable biome could become highly flammable if climate limitations to fire occurrence are relaxed.  However, no unambiguous evidence exists that fire frequencies were higher in the past 60 years than in the paleorecord of the late Quaternary.  Statistical analysis of historical data reveals strong linkages between climate and tundra burning at annual timescales. A generalized boosting model based on summer (June-August) temperature and precipitation alone explains approximately 90% of the variance in annual area burned from 1950 - 2009 in Alaska, with apparent thresholds to burning at ~11 °C and ~150 mm.  Applying these relationships to 21^st-century climate scenarios suggests that annual area burned will approximately double in Alaskan tundra.  Fires can release ancient carbon from tundra ecosystems and catalyze other biogeochemical and biophysical changes, with local to global consequences.  Given the likelihood of elevated tundra burning in coming decades, land managers and policy makers need to increasingly consider the ecological and socioeconomic impacts of fire in the Far North.