Global change impacts on sub-arctic palsa mires and greenhouse gas feedbacks to the climate system (PALSALARM)

Palsa mires are subarctic mire complexes with permanently frozen peat hummocks. They are marginal permafrost features that occur uniquely at high latitudes in parts of Fennoscandia, Russia, Canada and Alaska. They are also known to be biologically heterogeneous environments with a rich bird species diversity, and are listed as a priority habitat type by the European Union. In recent decades there has been an alarming decline of palsa mires in northern Europe, which is thought to be due to regional climatic warming. The degradation of these permafrost features has been accompanied by the release of methane and carbon dioxide to the atmosphere, both important greenhouse gases. It also threatens some of the most important breeding sites for migratory birds in northern Europe. This project brought together research groups from four institutions in the Nordic region who had hitherto worked largely independently on different aspects of palsa mires. The central aim of the study was to estimate future changes in the distribution of palsa mires in Fennoscandia, and the implications of these changes for greenhouse gas budgets and nature conservation. The project had four specific objectives: (i) to map the current distribution of palsa mires; (ii) to model future changes in palsa mire distribution due to projected climate warming; (iii) to estimate future changes in the CH4 and CO2 budgets of palsa mires; and (iv) to assess the ecosystem implications of palsa mire degradation and investigate possible conservation measures.