'Arctic hotspot complexes' proposed priority sites for studying and monitoring effects of climatic change on arctic biodiversity
The concept 'arctic hotspot' is proposed here for an area within the Arctic with an extrazonally warm climate, resulting in thermophilous biodiversity elements not found in its surroundings. Together with adjacent areas with zonal and extrazonally cold climates, these make up 'arctic hotspot complexes', with extraordinarily strong bioclimatic gradients. Horizontal temperature gradients should at least correspond to 'one bioclimatic subzone', but these could be realized along longer distances when local arctic hotspots are not only isolated, but situated within regionally defined hotspots. Topographic features and/or strong continentality explain the extrazonally warm climate and the resulting climatic gradient.An analysis of Svalbard resulted in four proposed arctic hotspot sites, and five more sites are included as examples from Canada, Greenland and Russia. Due to its topography, Greenland probably has the highest concentration of arctic hotspots. A number of arctic hotspot complexes contain centres which are boreal enclaves. There is a need to identify arctic hotspot sites including their biodiversity and bioclimatic characteristics. There is also a need for having arctic hotspot sites evaluated for inclusion in climate change-related studies and monitoring programs, as this may facilitate meso-scale approaches and collection of high-quality field data, related to remote sensing and modeling efforts. This may also facilitate integration of population data in bioclimatic contexts, as arctic hotspot sites can be expected to act as future migration centres for isolated populations exposed to climatic warming.