Palsa mires of the Northern Hemisphere: environmental characteristics, degradation, and morpho-ecological state

Palsa mires, characteristic permafrost peatlands of northern regions, are increasingly threatened by climate change due to permafrost degradation. As the permafrost thaws, the palsa mounds disappear, the topography of the mires becomes more uniform, and the landscape changes. These changes in the abiotic environment may also affect the biodiversity of northern ecosystems, as the diverse habitats created by the palsa mounds disappear and organisms lose important growing, feeding, and breeding sites. In addition, permafrost degradation releases greenhouse gases, such as carbon dioxide and methane from decomposing peat, which may further accelerate the global climate change.

This doctoral dissertation investigates the environmental factors that influence the occurrence, state, and degradation of palsa mires, using remote sensing data and statistical modeling. The analyses span from the local to circumpolar scales. The results show that soil moisture and climatic factors, such as air temperature and precipitation, best explain the distribution of palsa mires across the Northern Hemisphere. Based on three climate change scenarios, the study predicts that the suitable environments for palsa mires will almost completely disappear from the northern permafrost region by the end of this century if climate change is not effectively mitigated. Even under the most optimistic scenario, up to 75 percent of the suitable environments are at risk of disappearing. The research also found that less than one-third of Finnish palsa mires remain in good ecological state and that the total area of palsa mounds in the northern Lapland has decreased by up to 76 percent since the 1960s.

The dissertation improves our understanding of the environmental factors driving the occurrence and state of palsa mires, and can help to predict future changes in their distribution. The findings can be used, for example, to assess the impact of climate change on global greenhouse gas emissions and to plan conservation strategies to maintain the diversity of the northern environments.