It is estimated that 1,400 gigatonnes of organic carbon were captured in permafrost soils as a result of the decay of plants and fauna during the last ice age. For comparison there is roughly 800 gigatonnes of carbon in the atmosphere. If a significant amount of the carbon captured in permafrost soils were released, it would contribute significantly to accelerating the increase in atmospheric greenhouse gas concentrations. A recent study uses remote sensing to document the range expansion of North American beaver into the Arctic region of northwest Alaska which suggests that permafrost thawing may be expanding. Since 1999, 56 new beaver pond complexes were identified, indicating that beavers are colonizing a predominantly tundra region (18,293 square kilometers) of northwest Alaska. Beaver ponds and associated hydrologic changes are resulting from and contributing to thawing permafrost as pond formation increases winter water temperatures ponds and downstream.
Tundra be dammed: Beaver colonization of the Arctic, Ken D. Tape, Benjamin M. Jones, Christopher D. Arp, Ingmar Nitze, Guido Grosse. Global Change Biology, 30 May 2018, https://doi.org/10.1111/gcb.14332