Terrestrial Ecosystems Summary
Section Coordinator: Michael Svoboda
Canadian Wildlife Service, Environment Canada, Whitehorse, YT, Canada & CAFF/CBMP
December 4, 2012
The 2012 Terrestrial Ecosystem Section of the Arctic Report Card includes primary producers (vegetation), herbivores (lemmings & caribou and reindeer) and predators (Arctic fox). Another essay highlights changes in arctic migratory wader (shorebird) populations, which introduces and emphasizes the influence of southern stressors and drivers on Arctic wildlife. The five essays highlight meaningful detectable changes of regional, continental and global significance, suggest key factors responsible for the changes (be it climate, anthropogenic or both) and illustrate the connections between the Arctic marine and terrestrial ecosystems. An example is the direct link between increases in Arctic tundra vegetation productivity and earlier peak productivity in many parts of the Arctic on one hand, and the increasing duration of the open water season and decreasing summer sea ice extent in the Arctic Ocean on the other. Information from long-term, ground-based observations shows that, in addition to increasing air temperatures and loss of summer sea ice, widespread greening is also occurring in response to other factors. These include landslides and other geomorphological processes related to warming permafrost, tundra fires and increased human presence in the Arctic.
The impacts of increased biomass production in Arctic tundra ecosystems on arctic wildlife are unclear. Migratory caribou/reindeer appear to be within known ranges of natural variation, with many herds that have experienced declines in the past decade beginning to stabilize or increase. Like caribou, lemming abundance dramatically alters the composition of the tundra food web, the biomass and structure of vegetation, and the productivity of numerous other birds and mammals that depend on them as a food source. Lemming populations are cyclic, with the recovery to high populations after low density years most often associated with a period of successful breeding and recruitment of young under the winter snow. Regularity in cycle duration seems to be decaying, i.e., lengthening, in many Arctic regions, and cycle amplitude in some regions has collapsed to relatively low densities. Recent studies suggest a link between changes in the lemming population cycle and changes in the characteristics of the snow pack, e.g., duration and number of ice layers, and the subsequent impact on ground conditions, e.g., temperature and ice layers. One animal most directly affected by lemming population dynamics is the Arctic fox, which depends on them as a primary food source. In Europe, the Arctic fox population has not recovered from over-harvesting at the start of the 20th Century and the recent absence of lemming peaks; consequently, the Arctic fox has declined to near extinction in the European Arctic. In North America, the Arctic fox is abundant. In both regions, the Red fox has expanded northward into historic Arctic fox-only territories. The Red fox, twice the size of the Arctic fox with about twice the home range area, affects the Arctic fox via competition for resources and intra-guild predation.
At a more global scale, waders connect the Arctic to virtually all corners of the world, apart from Antarctica, via their migratory routes. This extensive range highlights the significance of extra-Arctic impacts on some populations that frequent the Arctic. Waders are by far the most numerous and species rich taxa among all Arctic waterbirds and serve as good indicators of the state of global coastal and inland wetlands. Current data suggest a profound and widespread decline in wader population abundance, due primarily to hunting and harvesting, pollution and habitat loss.