Could horses be the saviour of swathes of permafrost? Researchers investigate

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Yakutian horses are the main grazers at Pleistocene Park, and the most efficient in finding food in deep snow.
Yakutian horses are the main grazers at Pleistocene Park, and the most efficient in finding food in deep snow. They eat only grasses and herbs so they do not play an important role in vegetation shifts. © Pleistocene Park

Horses could play a crucial role in prolonging the life of vast areas of permafrost, according to researchers in Germany.

Permafrost soils in the Arctic region are thawing. As they do, large additional quantities of greenhouse gases could be released, accelerating climate change.

In Russia, experiments are now being conducted in which herds of horses, bison and reindeer are being used to combat this effect.

A wisent (European bison) with several musk ox in Pleistocene Park.
A wisent (European bison) with musk oxen in Pleistocene Park. © Pleistocene Park

A study by the University of Hamburg, reported in the journal Scientific Reports, confirms that this method could indeed significantly slow the loss of permafrost soils.

Theoretically, 80 percent of all permafrost soils around the globe could be preserved until the year 2100, as has now been demonstrated by Professor Christian Beer from the university’s Center for Earth System Research and Sustainability.

Beer is an expert on the permanently frozen soils found throughout the Northern Hemisphere.

If no action is taken to prevent it, half of the world’s permafrost will thaw by 2100.

The new study explores a somewhat unconventional countermeasure: resettling massive herds of large herbivores.

The inspiration came from Pleistocene Park in Chersky, a city in northeast Russia.

Russian scientists Sergey and Nikita Zimov resettled herds of bison, wisents, reindeer and horses there more than 20 years ago, and have been observing the effects on the soil ever since.

In winter the permafrost in Chersky is around minus 10 degrees Celsius; at temperatures down to minus 40 degrees Celsius, the air is far colder.

Thanks to ample snowfall, there is a thick layer of snow cover that insulates the ground from the frigid air, keeping it “warm.”

When the snow cover is scattered and compressed thanks to the grazing animals’ stamping hooves, its insulating effect is dramatically reduced, intensifying the freezing of the permafrost.

“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,” Beer says.

The long-term experiments conducted in Russia show that, when 100 animals are resettled in an area of one square kilometre, they cut the mean snow cover height in half.

Beer and his colleagues wanted to determine what effect this could produce when applied to all Arctic permafrost soils as a whole. Could the animals’ influence, at least in theory, even be enough to mitigate intensive warming of the atmosphere and stop the thawing of the permafrost?

Bison and musk oxen at Pleistocene Park.
Bison and musk oxen at Pleistocene Park. © Pleistocene Park

For the purposes of his study, Beer used a special climate model that can simulate such temperature processes on the land surface over the course of an entire year. The results show that if emissions continue to rise unchecked, we can expect to see a 3.8-degree Celsius increase in permafrost temperatures, which would cause half of all permafrost to thaw.

In contrast, with animal herds, the ground would warm only by around 2.1 degrees — 44 percent less, which would be enough to preserve 80 percent of the current soils, as the model shows.

Yakutian horses in  Pleistocene Park
© Pleistocene Park

“It may be utopian to imaging resettling wild animal herds in all the permafrost regions of the Northern Hemisphere,” the Earth system expert concedes.

“But the results indicate that using fewer animals would still produce a cooling effect. 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.”

Beer and his team also considered the potential side effects of the approach. For example, in summer the animals destroy the cooling moss layer on the ground, which warms it additionally. This aspect was also taken into account in the simulations, but the positive impact of the snow effect in winter is several times greater.

As a next step, Beer plans to collaborate with biologists, in order to investigate how the animals would actually spread across the landscape.

Beer C, Zimov N, Olofsson J, Porada P, Zimov S: Protection of Permafrost Soils from Thawing by Increasing Herbivore Density (2020); Scientific Reports http://www.nature.com/articles/s41598-020-60938-y DOI: 10.1038/s41598-020-60938-y

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