text: The authors write that "woody species are predicted to increase in tundra ecosystems as a result of global climate change (Chapin et al ., 1996; Epstein et al ., 2000)," and, in fact, it has been found that in response to rising air temperatures, "trees have established where they did not previously occur, both in alpine areas (Wardle and Coleman, 1992; Peterson, 1994; Kullman, 2001, 2002), and in arctic tundra (Lescop-Sinclair and Payette, 1995; Danby and Hik, 2007)," while "increasing shrub abundance also has been reported in alpine (Klanderud and Birks, 2003) and arctic locations (Sturm et al ., 2001; Tape et al ., 2006; Wilson and Nilsson, 2009)."