Terrestrial Ecosystems Summary
Section Coordinator: Michael Svoboda
Canadian Wildlife Service, Environment Canada, Whitehorse, YT, Canada & CAFF/CBMP
November 8, 2013
The Terrestrial Ecosystems Section of Arctic Report Card 2013 updates previous accounts of vegetation and migratory tundra caribou and reindeer (Rangifer), and introduces the inaugural Muskox (Ovibos moschatus) essay, which demonstrates the immense impact of conservation efforts on arctic wildlife.
It is not surprising that changes in vegetation and habitat quality are closely scrutinized, as many key wildlife species depend on the short summer growing seasons for access to food. Information from long-term, ground-based observations shows that, in addition to increasing air temperatures and loss of summer sea ice, widespread increased 'greening' (a measure of vegetative productivity), is continuing in response to other factors. These include increases in the length of the growing season, large-scale atmospheric circulation patterns, and regional summer cloud cover (see the essay on Vegetation). Substantial tall shrub and tree expansion at the forest-tundra ecotone in Siberia has also been linked to active cryospheric disturbances.
The impacts of increased biomass production in Arctic tundra ecosystems on arctic wildlife are unclear. As is often the case with arctic wildlife (e.g., migratory birds - see the essay on Seabirds in Report Card 2012), many factors such as disease, hunting rates, and changes to management regimes have demonstrated significant influence on productivity and abundance. This complexity is reflected in both the caribou/reindeer and muskox abundance essays. Nevertheless, migratory caribou and reindeer appear to be within known ranges of natural variation, with many herds having experienced massive declines in the past decade (see the essay on Migratory Tundra Rangifer).
In contrast to caribou, muskoxen have spread geographically and increased in number from reduced ranges after historic declines (see the essay on Muskoxen). Aided by significant re-introductions and conservation efforts, muskox populations appear to be stable/increasing since the 1970s. Although muskoxen have shown sensitivity to over-harvesting and disease, their resilience to extreme weather periods/events have also been recorded. For example, in the mid-2000s on Wrangel Island, east Siberia, several years of late autumn freezing rain, effectively encased food sources in ice rather than under snow. This event caused large declines in Rangifer populations, but had little effect on muskoxen numbers.