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The Greening of Canada's Herschel Island: A Fine Example of the Biological Awakening of the Circumpolar Arctic
Myers-Smith, I.H., Hik, D.S., Kennedy, C., Cooley, D., Johnstone, J.F., Kenney, A.J. and Krebs, C.J. 2011. Expansion of canopy-forming willows over the twentieth century on Herschel Island, Yukon Territory, Canada. Ambio 40: 610-623.

What was done
Noting that "canopy-forming shrubs are reported to be increasing at sites around the circumpolar Arctic," the authors (1) examined historic photographs, (2) repeated vegetation surveys, and (3) conducted monitoring of long-term plots on Canada's Herschel Island (69.57°N, 138.91°W), in order to see what had occurred over the past century on this 100-km2 parcel of land just off the western Arctic coast of Canada's Yukon Territory.

What was learned
Based on all three of their lines of research, Myers-Smith et al. "found evidence of increases of each of the dominant canopy-forming willow species (Salix richardsonii, Salix glauca and Salix pulchra), during the twentieth century," along with evidence that "the majority of willow patches for each of these species became established between 1910 and 1960," but "with stem ages and maximum growth rates indicating that some patches could have established as late as the 1980s."

What it means
The seven scientists report that their findings represent but one example of the 20th-century greening of the Circumpolar Arctic, noting that "recent evidence indicates an expansion of canopy-forming shrubs at sites on the North Slope of Alaska (Sturm et al., 2001; Tape et al., 2006), on the coast of the Northwest Territories (Lantz et al., 2009), in Northern Quebec (B. Tremblay et al., personal communication), and in northern Russia (Forbes et al., 2010a)." In addition, they indicate that "in Arctic Alaska, canopy cover of alder shrubs has increased by 14-20% on average within the last 40 years, with increases of up to 80% in some areas (Tape et al., 2006)." And they say that "studies of population structures of shrub and tree species indicate advancing of shrubs up slopes in alpine tundra ecosystems in subarctic Sweden (Hallinger et al., 2010)," as well as in sites in Norway (Hofgaard et al., 2009), while further noting that "local indigenous Nenets people in the western Russian Arctic report increasing willow shrubs (Forbes et al., 2010b)" and that "similar observations of vegetation change by Inuit have been reported in Arctic Canada (Thorpe et al., 2002)."

Last of all, the team of Canadian researchers states that "pollen records indicate that willows were widespread in Arctic ecosystems during warmer periods after the last glacial maximum (Brubaker et al., 1983; Bigelow et al. (2003)." And these several observations would seem to suggest that the entire Circumpolar Arctic is in the process of returning to what could be called the good old days, when that part of the planet was a whole lot greener - and a whole lot livelier - than it has been for a long, long time.

Bigelow, N.H., Brubaker, L.B., Edwards, M.E., Harrison, S.P., Prentice, I.C., Anderson, P.M., Andreev, A.A., Bartlein, P.J., Christensen, T.R., Cramer, W., Kaplan, J.O., Lozhkin, A.V., Matveyeva, N.V., Murray, D.F., McGuire, A.D., Volodya Y., Razzhivin, V.Y., Ritchie, J.C., Smith, B., Walker, D.A., Gajewski, K., Wolf, V., Holmqvist, B.H., Igarashi, Y., Kremenetskii, K., Paus, A., Pisaric, M.F.J. and Volkova, V.S. 2003. Climate change and Arctic ecosystems: 1. Vegetation changes north of 55 N between the last glacial maximum, mid-Holocene, and present. Journal of Geophysical Research 108: 10.1029/2002JD002558.

Brubaker, L.B., Garfinkee, H.L. and Edwards, M.E. 1983. A late Wisconsin and Holocene vegetation history from the central brooks range: Implications for Alaskan palaeoecology. Quaternary Research 20: 194-214.

Forbes, B.C., Fauria, M.M. and Zetterberg, P. 2010a. Russian Arctic warming and 'greening' are closely tracked by tundra shrub willows. Global Change Biology 16: 1542-1554.

Forbes, B.C., Stammler, F., Kumpula, T., Meschtyb, N., Pajunen, A. and Kaarlejarvia, E. 2010b. High resilience in the Yamal-Nenets social-ecological system, West Siberian Arctic, Russia. Proceedings of the National Academy of Science USA 106: 22,041-22,048.

Hallinger, M., Manthey, M. and Wilmking, M. 2010. Establishing a missing link: Warm summers and winter snow cover promote shrub expansion into alpine tundra in Scandinavia. New Phytologist 186: 890-899.

Hofgaard, A., Dalen, L. and Hytteborn, J. 2009. Tree recruitment above the treeline and potential for climate-driven treeline change. Journal of Vegetation Science 20: 1133-1144.

Lantz, T.C., Kokelj, S.V., Gergel, S.E. and Henry, G.H.R. 2009. Relative impacts of disturbance and temperature: Persistent changes in microenvironment and vegetation in retrogressive thaw slumps. Global Change Biology 15: 1664-1675.

Sturm, M., Racine, C.H. and Tape, K.D. 2001. Increasing shrub abundance in the Arctic. Nature 411: 546-547.

Tape, K.D., Sturm, M. and Racine, C.H. 2006. The evidence for shrub expansion in Northern Alaska and the Pan-Arctic. Global Change Biology 12: 686-702.

Thorpe, N., Eyegetok, S., Hakongak, N. and Elders, K. 2002. Nowadays it is not the same: Inuit Quajimajatuqangit, climate caribou in the Kitikmeot region of Nunavut, Canada. In: Krupnik, I. and Jolly, D. (Eds.), The Earth is Faster Now: Indigenous Observations of Arctic Environmental Change, Arctic Research Consortium of the United States/Smithsonian Institution, Fairbanks/Washington, DC., pp. 198-239.

Reviewed 2 May 2012