Effects of climate change on the distribution and development of palsa peatlands: background and suggestions for a national monitoring project
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Hofgaard, A. Effects of climate change on the distribution and development of palsa peatlands: background and suggestions for a national monitoring project. NINA Project Report 21. 32pp. Anticipated global warming trend especially at high latitudes has increased the need for, and importance of, monitoring programs designed to track the response of fragile ecosystems and edaphic and biotic structures they depend on. Palsa peatlands belong to permafrost landforms that incorporate both fragile edaphic structures and fragile biotic communities. It has been hypothesized that a further climatic warming and/or precipitation increase will result in melting of most palsas (i.e. frozen peat-covered mounds protruding above the surface of the surrounding peatland) within a few decades at the most marginal sites. These sites will then also be the most sensitive to any human activities affecting the vegetation structure, peat cover or hydrological properties of the peatlands. Under increased climatic marginalization, even benign human impact may destabilize entire edaphic and biotic structures and consequently jeopardize the long-term survival of depending species locally and regionally. This deserves increased consideration in management or conservation plans for palsa peatlands. The spatial and temporal distribution of palsas depends on local and regional climatic factors and on how the climate is changing at scales of decades and centuries. In Norway palsa are common features in peatlands mainly in two regions, one in the south restricted to Dovre-Femunden, and one broader northern covering Troms and Finnmark. Palsa peatlands are characterized by a mosaic of palsas, peat areas without permafrost, wet sedge areas, and ponds. The system is highly dynamic through time due to growth and decay of palsas. The development of palsa peatlands during the later half of the 20th century has been dominated by decline. The documentation is however slightly biased as it has largely focused on the development of dominating “late successional” palsa features and a holistic picture is herewith obscured. A monitoring program need to capture the constant flux of changes caused by permafrost alternations, including different palsa structures, development of ponds and colonization of ponds along with analyses of vegetation structure and land use changes to be able to draw profound conclusions. There is a general lack of organized or methodologically consequent projects monitoring palsa peatland dynamics in Scandinavia. Establishment of a Norwegian long-term monitoring program based on testable methods would provide high quality information for preservation and management authorities and the scientific community both nationally and internationally. Through such a program, palsa peatland dynamics would form an efficient indicator of climate change and its effects. The outline for a monitoring program including suggestions for methods and study areas is given in the present report.