TERRESTRIAL ECOSYSTEMS ON SVALBARD: HETEROGENEITY, COMPLEXITY AND FRAGILITY FROM AN ARCTIC ISLAND PERSPECTIVE

Abstract:Svalbard is an archipelago at the north-western edge of the Barents Sea. Despite its extreme northerly position, the climate is relatively mild in the western part of the archipelago. This is due to the warm North Atlantic Current reaching Spitsbergen, the largest island, causing temperatures there to frequently fluctuate around freezing, even in winter. Svalbard ecosystems share some attributes typical of islands. However, in spite of the limited land area there is large heterogeneity among ecosystems on different spatial scales: three out of five Arctic bioclimatic subzones occur in the archipelago, stretching from extremely low productive polar deserts to relatively productive tundra. Plant community data presented in this paper demonstrate that plant communities in mesic (zonal) habitats are well differentiated among the different bioclimatic subzones. Within a subzone, strong community differentiation occurs between mesic and ridge habitats in the two warmest zones, but not in the coldest, the polar desert. Relative to 'mainlands', species diversity is low on Svalbard and terrestrial food webs are simple, with strong links to marine food webs. However, fully accounting for the invertebrate components of the food webs reveals a considerable complexity that may contribute to ecosystem robustness. Fragility of the terrestrial ecosystems on Svalbard is discussed in terms of island characteristics. It is concluded that these ecosystems are robust in terms of temporal variation in herbivore populations and climate, but are fragile in terms of human disturbance. Their fragility in terms of climate change is still an open question that needs more thorough evaluation.