As the Planet Warms, What Happens to the Reindeer?- page 2 | Science | Smithsonian
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(Randall Hyman)

As the Planet Warms, What Happens to the Reindeer?

Ecologists are racing across the ice to find out how climate change will affect the Arctic natives

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Anyone leaving Longyearbyen carries a rifle, in case of running into polar bears. A week and a half before I arrived, a couple shot and killed a male that had worked his way partway through the window of their cabin, after throwing heavy mittens and a cup and shooting off signal flares didn’t deter him. Scientists go to a shooting range on the hillside above the airport every year before heading out into the field. “The Norwegians are always much better than me,” Albon says. If a polar bear ever did attack, “I would hand the rifle to one of them and say, ‘Here, you do it.’”

Albon first came to Spitsbergen in 1989 when a colleague he’d known in Cambridge clued him in to the reindeer that wander its valleys in groups of three to five, nibbling on herbs, grass and dwarf shrubs. Though Svalbard is high in the Arctic, vegetation does grow in lowlands near the coasts and in ice-free valleys during the short summer, thanks to warm Atlantic currents. The reindeer pack on fat while they can, and in the fall join up in bigger groups for the rut, when males use their antlers to battle over who gets to mate with females.

No one knows exactly how many reindeer live in all of Svalbard; they’re small and spread out, in unusually inhospitable terrain. It’s believed that most survive around ten years. Even if it were possible to get an accurate count for any given year, the population oscillates widely. If you had to make a bet at any one time, pick a number between 1,000 and 10,000, says Brage Bremset Hansen, a population ecologist at the Norwegian University of Science and Technology in Trondheim and the guy on the other end of Albon’s reindeer-catching net. Exactly how the animals got to this now-remote island isn’t clear either, but a founding population must have walked over the sea ice thousands of years ago, possibly from North America or Russia. Any such link is long gone, leaving the reindeer isolated even in winter.

It’s cold in April in the Arctic—the temperature was 5 degrees Fahrenheit the day White 150 was caught, right around the average winter temperature near Longyearbyen between 1961 and 1990. But the weather is warming. For the last three decades, average winter temperatures have hovered closer to 10 degrees Fahrenheit. Warmer weather might sound like a good thing for the reindeer. After all, a longer summer means a longer growing season. But Albon and his colleagues think that the more important factor for reindeer health is not how much they eat in the summer but in the winter. And, unfortunately for these ungulates, warmer winters lead to more rain.

During the winter, Svalbard reindeer paw through the snow to get at lichen and plants. But after a rain the water freezes, encasing the vegetation in a hard ice shell and making it impossible for the deer to obtain dinner. In a rainy winter, animals starve. “Although they’ve got capacities to put fantastic quantities of fat on in the summer, they can’t actually survive the nine months of winter on that,” Albon says. “It’s not enough.”

The year 2012 was particularly rough. Nearly two inches of rain fell over a four-day period in late January and a six-inch-thick layer of ice formed on the ground under the snow. The famine conditions were reflected in data collected that winter by Albon and his team, who found that the average weight of female adults (which the team concentrates on) was 103 pounds—around 20 pounds lower than in good times. Fifty-nine percent of female reindeer were pregnant, a lower than usual rate, and one in ten of those fetuses was already dead when the researchers made their rounds. Though the animals can rebound from a bad year if a better year follows, two bad years in a row (a situation that hasn’t yet occurred, at least not since Albon started his study) could be a serious blow to the population. Early in the study, bad years were rare, with one in 1996 and the next not until 2002. But they seem to be coming more often: 2008, 2010 and 2012 were rainy.

The year I went out, 2013, was colder, and the scientists found no measurable ice on the ground. The average weight of female adults was 126 pounds, one of the highest weights ever recorded, and almost all of those females were pregnant, with no dead fetuses. “In general,” though, Albon says, “things have been getting tougher and the reindeer have been getting smaller.”

Not just reindeer are at risk. Last year, Hansen, the Trondheim population ecologist, published a paper in the prestigious journal Science showing that a warm winter with a lot of rain also leads to declines in a vole, a plant-eating bird known as the Svalbard rock ptarmigan and the Arctic fox (with a year lag), suggesting changes in weather could crash multiple populations simultaneously, threatening an entire self-sustaining Arctic community.

Scientists have generally agreed that a warming globe means animals will move if they can, following their comfort zones. Populations of everything from butterflies to fish have been observed shifting toward the poles or up mountainsides. But the details of such climate-induced migrations—which species will move when and why—are challenging to study, because most ecosystems are incredibly complex.

One of the charms of studying reindeer in Svalbard is the simplicity. It’s a sort of desktop terrarium version of an Arctic ecosystem. The reindeer inhabit one of the world’s simplest food webs. They have no predators, other than people authorized to take part in a small annual hunt. Wolves and wolverines don’t live here. Polar bears chase marine mammals, and Arctic foxes go for smaller prey or carcasses. What’s more, there’s little development to interfere with the reindeers’ lifestyle; the oil industry’s roads and pipelines don’t reach this far. Even coal mines are absent from Albon’s study area.

That leaves one variable: weather. “The thing that’s going to kill you is the winter,” says Perry Barboza, a scientist at the University of Alaska-Fairbanks who studies how food availability and quality affect the survival and growth of animals. “Svalbard gives you this wonderful opportunity to get reliable data every year.” And because of the ecosystem’s streamlined nature, Svalbard can serve as a kind of baseline for what’s happening in places with much more complexity, and more animals.

Still, it’s too soon to know exactly how the reindeer would react to a series of rainy winters. Albon doesn’t bet on extinction: “Not everywhere would be iced to the same degree,” he says. “They can move.” He suspects the reindeer will head to the eastern part of the island first, away from the North Atlantic Current’s warming influence. But will the entire ecosystem shift intact? Will the eastern slopes support as many reindeer?

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