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[universal-salvage.org.uk]
"More beasts, less burden: Large animals could help keep permafrost frozen.
Strangely enough, one way to slow the thawing of permafrost is to reintroduce massive herds of large, plant eating animals to the Arctic landscape to mimic the days when millions of mammoths roamed the Siberian steppes. Although the idea may sound like science fiction, it is based in sound ecology. “Snow is like a down jacket that keeps the ground warm,” University of Alaska–Fairbanks researcher Katey Walter points out. “As the activity of animals compresses the snow or removes it through their foraging, the cold winter temperatures can penetrate deeper into the ground and keep the permafrost frozen.”

[mysteriousuniverse.org]

[www.livescience.com]