Assessing the impact of climate change-induced catastrophic disturbances for population viability of the endangered Peary caribou in the Canadian High Arctic.
Tews, Joerg*,1, Ferguson, Michael2, Fahrig, Lenore1, 1 Geomatics and Landscape Ecology Research Laboratory (GLEL), Ottawa, Ontario, Canada2 Nunavut Wildlife Service, Pond Inlet, Nunavut, Canada
ABSTRACT- The Peary caribou (Rangifer tarandus pearyi) is the northernmost distributed caribou subspecies in North America and occurs in five populations across the Canadian High Arctic. Due to drastic population crashes in the 70s and 90s it has been recently designated as endangered. There is strong evidence that these population crashes were triggered by catastrophic, density-independent climatic disturbances. In particular, unusually warm weather in the fall or spring resulting in ice crusts or winters with heavy snow fall made caribou forage temporarily inaccessible. It is suggested that such climatic conditions may increase under climate change. However, until now, there is large uncertainty how long-term changes of these disturbance regimes may affect population dynamics and persistence of this species. Here, we use a metapopulation model to study potential climatic effects on the population viability of the Peary caribou. In our model we vary four disturbance variables to study their impact on mean time to extinction of the metapopulation: (a) the mean frequency of disturbance events, (b) the average proportion of caribou die-off following a disturbance, (c) the spatial auto-correlation of disturbance events among the five populations, and (d) the temporal auto-correlation, i.e. whether disturbance years occur rather randomly or aggregated. Our results indicate that the average disturbance return interval of 10 years observed during the last four decades supports relatively stable population dynamics. However, if mean disturbance frequency may increase over the next decades, this may have profound consequences for the long-term persistence of the Peary caribou. In particular, we found that a concomitant increase in the spatial and temporal auto-correlation of disturbance events may significantly reduce the mean time to extinction, even under conservative projections of future climate change scenarios.
Key words: population viability analysis, metapopulation model, global change, density-independent mortality
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