Bringing Back the Herds to Keep the Permafrost Frozen

Arctic permafrost holds vastly more carbon than the atmosphere, and it is thawing partly because deep, undisturbed snow keeps winter cold from reaching the soil. Sergey Zimov's argument, tested at Pleistocene Park in northeastern Yakutia since 1996, is that the mammoth-steppe grazing herds that once churned that snow were doing climate work nobody replaced when they disappeared. The park covers 144 square kilometres with around 20 square kilometres fenced so far, and roughly 200 animals have been introduced — bison, musk ox, reindeer, Yakutian horses, moose, yaks and cattle — to graze, trample and convert mossy tundra back toward grassland. Ground temperature measurements under the trampled snow are the point of the experiment, and it remains exactly that: an experiment at small scale, arguing for something that would only matter if it worked across a continent.