Grazing may slow Arctic climate change, a new study finds — but we’re gonna need more reindeer.
By Bob Berwyn
Sami people from the Vilhelmina Norra Sameby fly a helicopter during a reindeer herding on October 28th, 2016, near the village of Dikanaess. (Photo: Jonathan Nackstrand/AFP/Getty Images)
Santa’s reindeer enjoy big headlines just once a year, but, in fact, they’re busy the rest of the time protecting their frozen turf from global warming. As millions of the Arctic ungulates graze the circumpolar tundra, they thin out shrubs, creating shiny clearings that bounce solar radiation back into space.
A new study from Norway says that this grazing can have a big effect on the regional energy balance by cooling surface temperatures and slowing the Arctic warm-up, which is already proceeding at double the average global pace.
“The whole northern Scandinavian tundra is grazed by reindeer. What we know is they can have a large effect in all these places…. If reindeer disappear, there will be a really negative effect,” says Johan Olofsson, a professor at Umeå University and co-author of the study.
Careful near-surface measurements across 36 plots near Troms, Norway, clearly show that heavily grazed sites absorb much less incoming solar heat, as the scientists report in the journal Environmental Research Letters. Without reindeer grazing, some areas could quickly be overgrown by heat-absorbing shrubs, Olofsson says.
Simply put, the darker, textured leaves of bushes are better at trapping the incoming heat from the sun. Grass, on the other hand, is quite light and features a smoother reflective surface. The scientists plan to study the effects of reindeer grazing on a larger scale, and Olofsson says there could be similar climate-changing effects in other ecosystems, including African savannas and the steppes of the American West.
Big regional shifts in the distribution of Arctic vegetation are already happening and “play an important role in determining the magnitude and timing of further regional and global climate warming,” as the researchers write. “Shrub expansion into tundra ecosystems may drive a positive global warming feedback … which ultimately amplifies regional warming and facilitates further shrub growth,” they conclude.
The reindeer grazing matters because the polar regions are the Earth’s vital air-conditioning system. They also buffer the effects of geological-scale climate change. And the ice caps prime the pump of Earth’s ocean circulation system with huge volumes of very cold and heavy, sinking water that drives currents for thousands of miles across vast depths.
At this point, there’s probably no way to avoid a complete summer meltdown of Arctic sea ice sometime in the next 50 to 100 years. But if greenhouse gas emissions are cut to near zero by mid-century, there’s a chance that the ice will re-form each winter, when the North Pole tilts away from the sun. And that could help prevent runaway global warming, which could happen if the Arctic tundra releases all the heat-trapping methane that’s now frozen in the deep organic ground.
The new study suggests that herbivore management could be a possible tool to combat future warming, according to lead author Mariska te Beest, from Umeå University. “Our results show that reindeer have a potential cooling effect on climate,” she says.
Reindeer distribution. (Map: Courtesy the
)
In short, the world needs more reindeer. Sad to say, the recent long-term population trend among reindeer is downward, according to a 2010 report from a biodiversity group working under the auspices of the intergovernmental Arctic Council.
Wild reindeer and caribou numbers dropped about 33 percent since the late 1990s, from 5.6 million down to 3.8 million. That decline may be part of a natural cycle, the report said, citing widespread population increases during the 1970s and ’80s, but it’s too early to say. The authors from the biodiversity group have acknowledged that the population might not bounce back: “[T]he recovery of most herds is not assured: recovery may be delayed or very slow, and some herds may disappear altogether,” they write.
