CR 32:1-12 (2006)  -  doi:10.3354/cr032001

ABSTRACT: Palsa mires are northern mire complexes with permanently frozen peat hummocks, located at the outer limit of the permafrost zone. Palsa mires have high conservation status, being characterized by a rich diversity of bird species and unique geomorphological processes. They are currently degrading throughout their distributional range, probably because of regional climatic warming. Distributions of palsas in Fennoscandia were modelled using 5 climate envelope techniques (generalized linear modelling, generalized additive modelling, classification tree analysis, artificial neural networks and multiple adaptive regression splines). The models were studied with respect to their sensitivity to altered climate. Climate change scenarios were applied to assess possible impacts on the palsa distribution during the 21st century. The models achieved a good to very good agreement with the observed palsa distribution and thus suggest a strong dependency on climate. Even small increases of temperature (1°C) and precipitation (10%) resulted in considerable losses of areas suitable for palsa development. Of the 5 models tested, 3 predicted the total disappearance of regions suitable for palsa development with an increased mean annual temperature of 4°C. Under climate change scenarios based on 7 Atmosphere-Ocean General Circulation Models (AOGCMs) the models indicated that the degradation of palsas will proceed very quickly. All but one climate scenario resulted in the total disappearance of suitable regions for palsa development by the end of the 21st century. Potential impacts of degrading palsa mires on biodiversity and carbon balance are the loss of habitat for migrating bird species and the increase in CH₄ emissions.

KEY WORDS: AOGCM · Climate envelope · Climate scenario · Palsa mire · Peatland · Permafrost · Uncertainty