Reindeer walking on snow in a forest
Reindeer—and horses, musk oxen, and bison, too—help Arctic permafrost cool down in winter by compressing snow cover. Credit: tarjapruess

Strategically resettling herds of large Arctic herbivores like reindeer, horses, bison, and musk oxen could help top layers of permafrost refreeze after summer thaw and stay frozen for longer. Environmental management like this could prevent 400 million square kilometers of Arctic permafrost from thawing by the year 2100.

“This type of natural manipulation in ecosystems that are especially relevant for the climate system has barely been researched to date—but holds tremendous potential,” lead researcher Christian Beer, a professor of dynamics of soil processes at Universität Hamburg in Germany, said in a statement.

In Sweden, the researchers observed that reindeer thinned snow cover by up to 82% compared with herd-free areas with similar snowfall. “Trampling down the snow by large herbivores in winter and the respective increase in snow density leads to a better connection of the atmosphere to the soil,” the team wrote. Thinner snow cover allows heat in the soil to escape to cooler air more efficiently as winter sets in.

Across the Eurasian landmass in northeastern Russia, scientists at Pleistocene Park, an ecosystem research and preservation site, have spent more than 20 years studying how herds of large Arctic herbivores have altered soil properties. Averaged over the year, soil temperature 1 meter deep was about 2°C colder in areas where herds graze compared with a herd-free control site, and the snow cover was patchier and thinner, too.

Horses trample snow at Pleistocene Park
Horses trample snow at Pleistocene Park. Credit: Pleistocene Park

The researchers used these measurements from Russia and Sweden as inputs into a global land surface climate model. Under unchanged emission conditions, introducing a Pleistocene Park–like density of herbivores to tundra ecosystems resulted in a 1.7°C (44%) drop in average global permafrost temperature and about 400 million square kilometers (37%) less thawed permafrost by the year 2100. The colder permafrost temperature might also slow down thawing beyond 2100. These results were published in Scientific Reports on 17 March.

At 114 animals per square kilometer, Pleistocene Park’s herbivore density is 20 times higher than the average herd density across the Arctic. It might not be feasible to replicate those conditions on a large scale, the scientists acknowledged. Their next steps aim to better understand the impacts of smaller herds on the permafrost and how resettling that many animals could change ecosystems in other climate-related ways.

“The results indicate that using fewer animals would still produce a cooling effect,” Beer said. “What we’ve shown here is a promising method for slowing the loss of our permanently frozen soils, and with it, the decomposition and release of the enormous carbon stockpiles they contain.”

“There are really no solutions to the increasing problem of permafrost thawing in the Arctic other than mitigation and adaptation around communities and infrastructure,” Duane Froese, who researches northern environmental change at the University of Alberta in Canada, told Newsweek. Froese was not involved with this research. “The present study, and the experiments at Pleistocene Park, are novel ideas about the problem.”

—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer


Cartier, K. M. S. (2020), Reindeer could trample permafrost thaw, Eos, 101, Published on 25 March 2020.

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