1 Section for Organismal Biology, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet2 Section for Environment and Natural Resources, Department of Food and Resource Economics, Faculty of Science, Københavns Universitet3 Forest and Lancscape College, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet4 Technische Universität München5 Forest and Lancscape College, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet6 Section for Environment and Natural Resources, Department of Food and Resource Economics, Faculty of Science, Københavns Universitet
disentangling effects of human disturbance and grazing
Shrub expansion has been observed widely in tundra areas across the Arctic. This phenomenon has been partially attributed to increasing temperatures over the past century. However, relationships among shrub expansion, grazing, and human disturbance have been studied little. SW Greenland is a subarctic to low-arctic region with a long and complex land-use history and only modest temperature increases over the past 50 years (0.2 °C decade-1), but changes in shrub cover have not previously been studied in this region. We compiled historical photographs of vegetation in SW Greenland (1898–1974) and repeated the photos in 2010 and 2011. Sixty-four photo pairs were cropped into 133 smaller units and classified by aspect, substrate stability, muskoxen grazing, and human disturbance. The photo material was evaluated by 22 experts with respect to changes in shrub cover, revealing a general increase across the whole data set, and in a subset including only undisturbed sites. Shrub cover increased most on E and SE slopes, in sites with stable substrate, and in areas characterized by human disturbance and without muskoxen grazing. The general shrub cover increase could be caused mainly by changed land-use intensity, but effects of the moderately increased temperatures cannot be ruled out.
Arctic, Antarctic, and Alpine Research, 2013, Vol 45, Issue 4, p. 515-525