Assessing the relative importance of climate change and human footprint impacts to caribou conservation in the Alberta Oil Sands Region

Woodland caribou declines have been linked to human land-use via mechanisms in which landscape change and habitat fragmentation increase caribou predation risk. Human land use is expected to increase availability of early-seral vegetation, increasing available forage for ungulates and omnivores, thereby bolstering predator densities. However, changes due to human land-use are occurring concurrently with rapid climate change, which may increase prey abundance by facilitating white-tailed deer expansion northward into caribou range as winters becomes less severe. It is important to understand the degree to which human land-use may be influencing predator and prey population carrying capacities in order to effectively manage a working landscape. We tested if human land-use has affected habitat quality for black bears and white-tailed deer, elevated populations of which are expected to increase predation risk to caribou directly (bears) or indirectly by supporting more predators (deer).

Results suggest overall magnitude of effect of human land-use on bear and deer habitat quality is relatively small and should be considered in relation to climate change effects such as (1) more frequent wildfires, (2) warmer, longer summers and extended growing season, and (3) milder winters that increase over-winter survival of deer. In coming work, this study will be put into broader context by examining mechanisms of increased deer and bear populations against i) increased predator hunting efficiency via increased movement rates, ii) increased predator-prey overlap and iii) climate change. Understanding relative importance of these pathways is important for caribou management strategies. For example, linear feature restoration may be effective for slowing predators and restoring functional response between predators and prey, but our work suggests this alone will not reduce densities of deer and black bears, supporting the need for multiple conservation actions in the short to medium term.