Winter Range Studies Of The Western Arctic Caribou Herd, Northwest Alaska

Abstract

Climate change is likely to bring a myriad of interrelated changes to the Arctic. One change is warmer and drier conditions that could increase the prevalence of wildfire in northwest Alaska. Wildfires destroy terricolous lichens that Western Arctic Herd caribou (Rangifer tarandus ) rely on during winter; taking decades to recover. My goals were to assess the recent (1950--2007) fire regime within the herd's range, identify characteristics of habitat selected by overwintering caribou, and determine the potential impacts of climate change on the fire regime and caribou winter range. I used a combination of existing data and information collected at vegetation plots to conduct these analyses. I found that wildfires in the tundra were relatively common from 1950--2007, covering approximately 10% of northwest Alaska. Tundra was > 4.5 times more likely to re-burn than boreal forest. This novel, yet intuitive finding could have serious implications if fire starts to become more common in the Arctic. I found that the average annual area burned more than doubled in years where mean August temperatures exceeded 11.7�C (53�F). Caribou use tundra and forested during winter but avoided recently (< 58 years) burned areas in both habitat types likely because they contained < 1/4 of the abundance of forage lichen species than unburned habitats. I found that lichen abundance was 3 times greater in the herd's current winter range versus its historic range -- supporting the theory that caribou shift ranges to compensate for deteriorating grazing conditions. Stand age was the most consistent correlate with lichen abundance. Dwarf birch (Betula spp.) was more abundant in recent burns which may facilitate the intensification of the future fire regime in the region. My modeling efforts revealed that wildfire is likely to become more prevalent, especially on the herd's core winter range, which could have deleterious impacts on caribou winter range and provide quality habitat for moose ( Alces alces). My results should provide a solid foundation to develop a science-based fire management plan for the Western Arctic Herd.