Consistent centennial‐scale change in European sub‐Arctic peatland vegetation toward Sphagnum dominance—Implications for carbon sink capacity

Climate warming is leading to permafrost thaw in northern peatlands, and current predictions suggest that thawing will drive greater surface wetness and an increase in methane emissions. Hydrology largely drives peatland vegetation composition, which is a key element in peatland functioning and thus in carbon dynamics. These processes are expected to change. Peatland carbon accumulation is determined by the balance between plant production and peat decomposition. But both processes are expected to accelerate in northern peatlands due to warming, leading to uncertainty in future peatland carbon budgets. Here, we compile a dataset of vegetation changes and apparent carbon accumulation data reconstructed from 33 peat cores collected from 16 sub‐arctic peatlands in Fennoscandia and European Russia. The data cover the past two millennia that has undergone prominent changes in climate and a notable increase in annual temperatures toward present times. We show a pattern where European sub‐Arctic peatland microhabitats have undergone a habitat change where currently drier habitats dominated by Sphagnum mosses replaced wetter sedge‐dominated vegetation and these new habitats have remained relatively stable over the recent decades. Our results suggest an alternative future pathway where sub‐arctic peatlands may at least partly sustain dry vegetation and enhance the carbon sink capacity of northern peatlands. We studied how European sub‐Arctic peatland (including permafrost and non‐permafrost peatlands) intermediate and dry microhabitats have changed in response to changes in climate during the past two millennia. We payed special attention to the recent past. During the past two millennia, most of the studied habitats had changed from wet (often dominated by sedges) toward drier conditions and often Sphagnum moss dominance. Moreover, the studied peatland microhabitats showed relatively stable vegetation compositions for the past decades. We speculate that high‐latitude peatlands may in the future sustain Sphagnum dominated vegetation, which could enhance their carbon sink capacity.