Wild horses, bison and reindeer could help slow the thawing of Arctic permafrost, a study has now shown. If more of these herbivores graze in the far north, this will churn up the insulating layer of snow on the soil. As a result, more cold gets underground and this can stop at least part of the warming. By 2100, the warming of the permafrost could be reduced by 44 percent, as the researchers have determined.
Enormous amounts of organic matter are stored in the permanently frozen Arctic soils – plant fibers, animal remains and other material that has been preserved uncorrupted at minus degrees for thousands of years. However, this subsurface is thawing with climate change. As a result, degradation processes begin in the soil, which decompose the organic material and release large amounts of carbon dioxide and methane. It is estimated that as warming continues, half of the permafrost could thaw by 2100.
Churning snowpack cools the ground
But there may be an amazingly simple way to at least slow down thawing of the permafrost. The research team led by Christian Beer from the University of Hamburg got the idea for this from observations by Russian colleagues in the Pleistocene Park near Chersky. In this 2000 hectare area in northeastern Russia, biologists released 20 groups of wild horses, reindeer, bison and wisents 20 years ago – the herbivores that used to live in large numbers in the cold plains of the far north. Since then, the researchers have observed how the presence of these animals affects the plant cover, the subsoil and the temperatures in the soil.
It showed that the presence of the animals in winter has a measurable effect on the soil temperature. In the search for feed, reindeer, wild horses and the like burrow the snow, scrape parts of the ground freely and trample the snow cover in other places. This reduces the heat-insulating effect of the snow cover and ensures that the cold of the air, which is down to minus 40 degrees, can penetrate unhindered into the ground. The observations in the Pleistocene Park showed that the presence of 100 of these large herbivores on an area of around one square kilometer can reduce the snow cover by half.
Protection for 80 percent of permafrost
“This type of natural manipulation in ecosystems has hardly been researched so far, but it has enormous potential,” says Beer. He and his team have now used the data from the Pleistocene Park, but also from northern Sweden, to estimate how great this potential actually is using a model. It showed that if climate change continues unchecked as described in the RCC 8.5 scenario of the IPCC, the temperatures in permafrost soil would rise by 3.8 degrees by the end of this century. As a result, around half of the permafrost would thaw. However, if large herds of herbivores disturb the snow cover, the heating of the subsurface would be 2.1 degrees lower – 44 percent less. That could be enough to prevent around 80 percent of the current permafrost soils from thawing by 2100, as the researchers report.
“It may sound utopian to resettle wild herds of animals in all permafrost regions in the northern hemisphere,” says Beer. The population densities examined ranged from 114 animals per square kilometer in the Pleistocene Park to 483 animals per square kilometer in the northern Swedish test area – this is very high and not feasible in the far north. “But our results indicate that the use of fewer animals would also have a cooling effect,” emphasizes the researcher. According to Beer and his team, this biological method therefore opens up a simple and natural way to at least slow down thawing of the permafrost. In the next step, more detailed field studies and models are now needed to determine more precisely how many animals one needs and what consequences this would have beyond the climate effect.
Source: University of Hamburg; Technical article: Scientific Reports, doi: 10.1038 / s41598-020-60938-y