Impacts of 21st century climate changes on flora and vegetation in Denmark

Abstract

In this paper we examined the potential impacts of predicted climatic\rchanges on the flora and vegetation in Denmark using data from a\rdigital database on the natural vegetation of Europe. Climate\rscenarios A2 and B2 were used to find regions with present climatic\rconditions similar to Denmark's climate in the year 2100. The\rpotential natural vegetation of Denmark today is predominantly\rdeciduous forest that would cover more than 90% of the landscape.\rSwamps, bogs, and wet forest would be found under moist or wet\rconditions. Dwarf shrub heaths would be naturally occurring on poor\rsoils along the coast together with dune systems and salt-marsh\rvegetation. When comparing the natural vegetation of Denmark to the\rvegetation of five future-climate analogue areas, the most obvious\rtrend is a shift from deciduous to thermophilous broadleaved forest\rcurrently found in Southern and Eastern Europe. A total of 983 taxa\rwere recorded for this study of which 539 were found in Denmark. The\rSorensen index was used to measure the floristic similarity between\rDenmark and the five subregions. Deciduous forest, dwarf shrub heath,\rand coastal vegetation were treated in more detail, focusing on\rpotential new immigrant species to Denmark. Finally, implications for\rmanagement were discussed. The floristic similarity between Denmark\rand regions in Europe with a climate similar to what is expected for\rDenmark in year 2100 was found to vary between 48-78%, decreasing from\rNorth to South. Hence, it seems inevitable that climate changes of the\rmagnitudes foreseen will alter the distribution of individual species\rand the composition of natural vegetation units. Changes, however,\rwill not be immediate. Historic evidence shows a considerable lag in\rresponse to climatic change under natural conditions, but little is\rknown about the effects of human land-use and pollution on this\rprocess. Facing such uncertainties we suggested that a dynamic\rstrategy based on modeling, monitoring and adaptive management is\radopted. Modeling techniques can be constantly improved, but will\rnever be perfect and should therefore be linked to a fine-masked\rnetwork of observatories to check model predictions and feed empirical\rdata back into the models for calibration and further development.