Description:
Dramatic changes, such as sea ice loss, are projected to occur in Arctic ecosystems over the next century. Understanding how the Arctic’s living resources, including its vertebrate species, are responding to these changes is essential in order to develop effective conservation and adaptation strategies. Arctic species that are adapted to these extreme environments are expected to be displaced, in part, by the encroachment of more southerly species and ecosystems. A total of 965 populations of 306 species (representing 35% of all known Arctic vertebrate species) were used to generate the Arctic Species Trend Index (ASTI). Presented in this figure is the terrestrial component of the ASTI. The moderate decline in the terrestrial index (–10%) is largely a reflection of declines (–28%) in terrestrial high Arctic populations (mostly herbivores, such as caribou, Rangifer tarandus, lemmings, and the High Arctic brent goose, Branta bernicla). Terrestrial low Arctic population increases (+7%) are driven, in part, by dramatically increasing goose populations, but may also reflect an ecological response to climatic changes whereby species with more southerly distributions are responding favorably to these climatic changes. This northward movement of southern species (e.g., red fox, Vulpes vulpes) coupled with increasing incidence of severe weather events in the high Arctic and changing tundra vegetation may explain, in part, the declines in terrestrial high Arctic populations and the possible negative impact on herbivorous species. This figure presents the index of terrestrial species disaggregated by Arctic boundary for the period 1970–2004 (high Arctic, n=25 species, 73 populations; low Arctic, n=66 species, 166 populations; sub-Arctic, n=102 species, 204 populations).