Reindeer keep vegetation in the Arctic short - this helps the climate (Photo: RelaxedPace / iStock)
Read aloud Reindeer are the defining mammals of the Arctic. In large herds, these ungulates move through the tundra. Now a field experiment reveals: The intensive grazing by reindeer has a positive effect on the local climate. Because reindeer keep bushes short and can not spread, grazed areas are brighter and reflect more sunlight. This reduces heat absorption and leads to a locally measurable cooling effect on the climate.

For the inhabitants of the far north they have always been an important livelihood: Already in the Stone Age, our ancestors hunted reindeer, ate their meat, processed their fur into blankets and clothes and used their bones as tools. Even today, the reindeer plays an important role for the Sami people in Scandinavia, the Nenets in Siberia and other peoples of the Far North. The ungulates belonging to the deer often roam the tundra in large herds of several thousand to find their food. They feed on grass that sprouts in the summer months, but also on woody scrub, moss, lichen and mushrooms. It has long been known that reindeer play an important role in the tundra landscape: they prevent the spread and growth of bushy plants and keep the areas free for grass and mosses. "The reindeer eat the woody plants and trample them down, which inhibits their spread and keeps the vegetation low", explain Mariska te Beest from the University of Umeå in Sweden and her colleagues.

The researchers have now investigated the impact of this grazing on the local climate in field trials in northern Norway. There, a fence built in the 1960s runs for miles through the tundra. It is designed to keep the semi-wild reindeer of the seeds in the officially released areas for summer grazing and to protect the area behind the fence. For decades, the area on one side of the fence has been intensively grazed, on the other side only a few wild reindeer graze from time to time. For the scientists, this was the perfect area to study the effect of reindeer grazing on vegetation and local climate. For their study, they repeatedly performed measurements of albedo, soil moisture and soil and air temperatures at locations on both sides of the fence and mapped the vegetation.

Reindeer pastures are cooler

The result: as expected, intensive grazing by reindeer had altered the composition of the tundra vegetation: on the side of the fence, protected from reindeer herds, heather and shrubs dominated, including many mid-high willow trees. On the intensely grazed side, on the other hand, mainly short grass grew, mixed with mosses and heather. This overall thinner plant cover also affected the physical characteristics of the landscape, the researchers report. The albedo of the tundra - and thus the amount of reflected sunlight - was on the grazed
Page significantly higher. The rather light, short grass reflected more radiation and thus absorbed less heat. The dark woody branches of the bushes in the barely grazed area, on the other hand, absorbed significantly more solar heat, as measured. As a result, the air temperatures directly above the ground on the bushy side were higher.

"Our results show that reindeer can have a potentially cooling effect on the local climate, " says te Beest. At first glance, this effect would appear only small, but it would be large enough to influence the regional radiation balance. According to the calculations, the difference in irradiated heat is at least 4.4 watts per square meter. "In terms of area, this is about the same as or even more than the warming of the atmosphere by doubling the carbon dioxide content, " the researchers explain. For the climate of the Arctic it could therefore be advantageous to let the reindeer graze freely. They keep the bushing of the tundra in check - and that in turn helps to make the already rapidly warming Arctic not even darker and thus more heat-absorbent. Although climate change is unlikely to stop, good management of reindeer herds could prove to be a valuable tool in the fight against Arctic warming, te Beest said. display

Source:

  • Mariska te Beest (Umeå University) et al., Environmental Research Letters, doi: 10.1088 / 1748-9326 / aa5128
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