Climate-Driven Effects of Fire on Winter Habitat for Caribou in the Alaskan-Yukon Arctic

Abstract

Climatic warming has direct implications for fire-dominated disturbance patterns in northern ecosystems. A transforming wildfire regime is altering plant composition and successional patterns, thus affecting the distribution and potentially the abundance of large herbivores. Caribou (Rangifer tarandus) are an important subsistence resource for communities throughout the north and a species that depends on terrestrial lichen in late-successional forests and tundra systems. Projected increases in area burned and reductions in stand ages may reduce lichen availability within caribou winter ranges. Sufficient reductions in lichen abundance could alter the capacity of these areas to support caribou populations. To assess the potential role of a changing fire regime on winter habitat for caribou, we used a simulation modeling platform, two global circulation models (GCMs), and a moderate emissions scenario to project annual fire characteristics and the resulting abundance of lichen-producing vegetation types (i.e., spruce forests and tundra >60 years old) across a modeling domain that encompassed the winter ranges of the Central Arctic and Porcupine caribou herds in the Alaskan-Yukon Arctic. Fires were less numerous and smaller in tundra compared to spruce habitats throughout the 90-year projection for both GCMs. Given the more likely climate trajectory, we projected that the Porcupine caribou herd, which winters primarily in the boreal forest, could be expected to experience a greater reduction in lichen-producing winter habitats (−21%) than the Central Arctic herd that wintered primarily in the arctic tundra (−11%). Our results suggest that caribou herds wintering in boreal forest will undergo fire-driven reductions in lichen-producing habitats that will, at a minimum, alter their distribution. Range shifts of caribou resulting from fire-driven changes to winter habitat may diminish access to caribou for rural communities that reside in fire-prone areas.

Observed and predicted effects of climate change on Arctic caribou and reindeer

“…Some studies have predicted less extreme changes in fire activity, with projections being near the upper limit of the historical range of fire occurrence (Girardin and Mudelsee 2008), though predicted future fire activity remains higher than the long-term average. This increase in the frequency of wildfire above historical levels has also been predicted for Arctic and northern biomes , with an associated predicted reduction in quality and availability of preferred winter barren-ground caribou habitat (Rupp et al 2006;Gustine et al 2014). Decreasing availability of quality winter forage can reduce the nutritional status of individuals during the winter (White 1983), and food limitation can lead to density-dependent effects, such as a decline in recruitment and female body size (Skogland 1986).…”

Distribution of barren‐ground caribou during winter in response to fire

“…Large losses in the amount of forested habitats occurred between 1990 and 2000 (GNWT 2010); approximately 30-35% of treed wintering areas burned (Chen et al 2013). Assuming that current climatic trends continue (IPCC 2007), an increase in fire activity across northern landscapes will further reduce the availability of forested taiga for caribou (Joly et al 2012, Gustine et al 2014). In addition, warmer annual temperatures may have consequences for lichen abundance via changes in the composition of plant communities (Cornelissen et al 2001, Olthof et al 2008.…”

“…Larger and more abundant burns, in addition to fewer older and lichen-rich stands, could significantly reduce the area or connectivity of high-quality habitat on the winter range of caribou in the Northwest Territories, Canada. A reduction in the availability or quality of winter range could lead to density-dependent effects of winter forage restriction including reductions in recruitment and body size of adult females (Skogland 1986), as well as altered distribution patterns (Joly et al 2003, 2007a, b, 2010, Gustine et al 2014) that would influence access to caribou by harvesters. However, it is important to consider the overall abundance of the herd within the context of a cycling population dynamic (Tyler 2010).…”

“…Future research should focus on the integration of empirical mechanistic-based studies on the individual components of caribou biology with longterm monitoring of body condition and population trends and models that link animal nutrition, habitat supply, and reproduction. Results would need to be considered in the context of observed oscillations in climate as well as suspected future changes that might influence fire and other environmental parameters such as snow and growing season (e.g., Gustine et al 2014). Ultimately, these studies would be linked to investigations on other seasonal ranges of migratory caribou (e.g., Russell et al 1993, Couturier et al 2009) to provide a more complete understanding of the factors that drive caribou population cycles.…”

The role of driving factors in historical and projected carbon dynamics of upland ecosystems in Alaska

“…, Gustine et al. ), and two process‐based ecosystem models that simulate (1) C and nitrogen (N) pools and CO 2 fluxes with the Dynamic Organic Soil version of the Terrestrial Ecosystem Model (DOS‐TEM; Yi et al. , ) and (2) CH 4 fluxes using the Methane Dynamics Module of the Terrestrial Ecosystem Model (MDM‐TEM; Zhuang et al.…”