Models show that if warming exceeds 2.7 °C, the Greenland icecap will probably melt (Pear-ce 2000). Almost all predictions demonstrate that the Greenland climate is likely to warm even more. Besi-des causing sea level rise, melting at higher latitudes will increase the availability of land for colonization by boita. Further, the current sout-hern border of the polar regions is likely to move north, shrinking the arctic biome, and favouring the establishment of new ecosystems on the icefree land. Why new ecosystems? Because the conditions with regard to dispersal and source areas of biota will have changed. As a consequence, shifts in diversity can be expected. In the current project we investigate this in a region with transition features, name-ly tundra on Disko Island (West-Geenland). This island is located at the border of two clima-to-logically defined zones: the transition between discontinu-ous and conti-nu-ous permafrost, and the transition between the Low Arctic and High Arctic. The region has quite high diversity, which can function as a source for nor-thern- or eastern-bound colonization in case of warming. In order to use the Disko Island situation as a model for other regions, the question must be answered what the sources of the cur-rent diver-sity are? Our attention will therefore focus on proces-ses which contributed to the `genesis' and the maintenance of this current diversity, i.e. disper-sal (I) and colonization (II). Furthermore, also stability (III) of the present populations (local extinction probability due to distur-ban-ce, especially climate-based) is critical to the regu-lation of local diversity. As a touchstone for current and future trends, paleo-fluc-tuati-ons (IV) of diversity will be examined in peat layers.