Arctic tundra fires: natural variability and responses to climate change

© The Ecological Society of America www.frontiersinecology.org A surveying scientists working in the Far North for tundra-fire observations and examining Canadian Government fire records, pioneer Arctic ecologist Ross Wein concluded that “tundra fires occurred infrequently, and were invariably small in areal extent... Little is known about the ecological significance of tundra fires” (Wein 1976). Modern satellite data have greatly enhanced scientists’ ability to detect tundra fires in remote high-latitude regions, but Wein’s conclusion holds for the biome as a whole: only 0.12% of vegetated circumpolar Arctic tundra has burned over the past decade (Figure 1a). Thus, the tundra biome is historically characterized by a general lack of burning, reflecting its location in one of the coldest environments on Earth (Figure 1, a and b) and its limited biomass. Against this historical backdrop, the frequency of tundra fires in recent years in some areas of the Arctic has been unexpectedly high. For example, during the summer of 2010, ~40 fires occurred in tundra ecosystems of the Noatak River Watershed in northwestern Alaska (AICC 2014) – a record-setting annual number for this area. Furthermore, tundra fires may have increased over time in terms of size and biomass consumed. On the North Slope of Alaska, where fires have been extremely rare over the past 10 000 years (Hu et al. 2010; Chipman et al. 2015), the Anaktuvuk River Fire (AR Fire) occurred in 2007, at a time when the region was unusually warm and dry (Jones et al. 2009; Hu et al. 2010). This single fire burned a 1039km area, more than doubling the total area burned during the previous 60 years in the region. These recent fires suggest that the future disturbance regime of tundra ecosystems will differ greatly from that of today if the trend of Arctic climate warming (Kaufman et al. 2009) continues, with far-reaching ecological and socioeconomic consequences (Mack et al. 2011; Joly et al. 2012). Are these recent tundra fires unprecedented or part of the natural fire cycle? 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 (eg Hu et al. 2010; Mack et al. 2011; Rocha and Shaver 2011a; Bret-Harte et al. 2013). This paper highlights some of the new findings about tundra-fire regimes – focusing on Alaska, where tundra-fire research efforts REVIEWS REVIEWS REVIEWS