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Regional Warming and Mountaintop Biodiversity
Reference
Kullman, L. 2007. Long-term geobotanical observations of climate change impacts in the Scandes of West-Central Sweden. Nordic Journal of Botany 24: 445-467.

What was done
The author analyzed the changing behavior of alpine and subalpine plants, together with shifts in their geographical patterns, during the past century, when air temperatures rose by about 1C in the Scandes of west-central Sweden. The "methodical approach," in his words, "also included repeat photography, individual age determinations and analyses of permanent plots."

What was learned
"At all levels, from trees to tiny herbs, and from high to low altitudes," according to Kullman, "the results converge to indicate a causal association between temperature rise and biotic evolution," indicating that "this appears to be an ecosystem on the brink of profound and imminent transformation." More specifically, he reports that "treeline advance since the early 20th century varies between 75 and 130 m, depending on species and site," and that "subalpine/alpine plant species have shifted upslope by [an] average [of] 200 m." In addition, he states that "present-day repetitions of floristic inventories on two alpine mountain summits reveal increases of plant species richness by 58 and 67%, respectively, since the early 1950s," adding, however, that "no species have yet become extinct from the highest elevations." Last of all, Kullman notes that his results "converge with observations in other high-mountain regions worldwide," citing the studies of Grabherr et al. (1994), Keller et al. (2000), Kullman (2002), Virtanen et al. (2003), Klanderud and Birks (2003), Walther et al. (2005) and Lacoul and Freedman (2006).

What it means
Kullman notes that the rapidity with which the observed ecosystem transformations have occurred "contrasts with earlier assumptions and theoretical generalizations, stressing significant time-lags or inertial adaptations to changed climatic conditions." Indeed, his results demonstrate the tremendous capacity for earth's vegetation to rapidly respond to climate change in dramatic ways that need not result in species extinctions, but that can lead to huge increases in ecosystem species richness, which is typically considered to be a desirable property of vegetative assemblages.

References
Grabherr, G., Gottfried, M. and Pauli, H. 1994. Climate effects on mountain plants. Nature 369: 448.

Keller, F., Kienast, F. and Beniston, M. 2000. Evidence of response of vegetation to environmental change on high-elevation sites in the Swiss Alps. Regional Environmental Change 1: 70-77.

Klanderud, K. and Birks, H.J.B. 2003. Recent increases in species richness and shifts in altitudinal distributions of Norwegian mountain plants. Holocene 13: 1-6.

Kullman, L. 2002. Rapid recent range-margin rise of tree and shrub species in the Swedish Scandes. Journal of Ecology 90: 68-77.

Lacoul, P. and Freedman, B. 2006. Recent observation of a proliferation of Ranunculus trichophyllus Chaix. in high-altitude lakes of Mount Everest Region. Arctic, Antarctic and Alpine Research 38: 394-398.

Virtanen, R., Eskelinen, A. and Gaare, E. 2003. Long-term changes in alpine plant communities in Norway and Finland. In: Nagy, L., Grabherr, G., Korner, C. and Thompson, D.B.A. (Eds.), Alpine Biodiversity in Europe. Springer, Berlin, Germany, pp. 411-422.

Walther, G.-R., Beissner, S. and Burga, C.A. 2005. Trends in upward shift of alpine plants. Journal of Vegetation Science 16: 541-548.

Reviewed 4 July 2007