25 November 2014

Siberian permafrost collapse

Rapid permafrost collapse shifts Siberian tundra to a methane source

Tundra ecosystems are undergoing rapid changes due to climatic changes, altering the vegetation composition and potentially destabilizing permafrost.

”Dansk omtale”

Decomposition of buried plant and animal remains in permafrost soils could lead to further climate warming by release of greenhouse gases carbon dioxide and methane. We performed an experiment in the tundra of Fareast Siberia, a region known for its enormous permafrost carbon stores, whereby we removed the dominant shrub species dwarf birch (Betula nana) to assess the effects on permafrost thaw. Surprisingly, the removal of shrubs led to a rapid incremental increase in summer permafrost thaw depth over the six years of the experiment. This deeper thaw led to a melt of ground-ice and collapse of the tundra surface, turning the original shrub mounds plots into ponds with standing water.

The rapid and substantial changes in thaw depth, hydrology and surface elevation dramatically altered the methane-balance from a source to a sink of methane, just five years after the start of the experiment. These results show that plants play a crucial role in the stabilization of permafrost. Our experimental perturbations of plant cover, which can occur naturally due to e.g. insect outbreaks, fungal infections or changes in reindeer grazing pressure, demonstrate the fragility of tundra ecosystem under a climate warming scenario that can modify the tundra carbon balance and thus feedback to global climate changes.

Nauta AL, Heijmans MMPD, Blok D, Limpens J, Elberling B, Gallagher A, Li B, Petrov RE, Maximov TC, van Huissteden J, Berendse F. Permafrost collapse after shrub removal shifts tundra ecosystem to a methane source. Nature Climate Change, published online November 24, 2014. DOI http://dx.doi.org/10.1038/nclimate2446