Terrestrial Antarctic ecosystems in the changing world: An overview

Although the Antarctic has avoided the worst effects of alien species, its future seems endangered due to increasing natural and man−made pressures. Rapid changes in three major environmental variables have occurred in the Antarctic region during the last decades. In the short term terrestrial biota are likely to benefit from reduced environmental stresses, but in the long run the colonization of the region by lower latitude species with greater competi− tive ability will become increasingly important and can lead to large−scale changes in biologi− cal composition and trophic complexity in some existing Antarctic terrestrial ecosystems. Moreover, the recent dynamic climate changes combined with human activities in the Antarc− tic region might modify the status of several alien species which have hitherto been consid− ered transient or persistent and could, therefore, become naturalized and threaten the native communities on a larger scale than today, or influence the status of naturalized species. Key wor ds: Antarctica, alien species, human impact.