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Reindeer are nearly synonymous with the polar North. Recognized for their imposing antlers, thick winter coats, and ability to survive in harsh environments, these majestic creatures are native to the frigid tundras and forests of North America, Siberia, and northern Europe. Historically, reindeer played a huge part in helping humans to settle these frigid latitudes, and are vital to the ecosystems and cultures of the places where they live and roam. But a new analysis suggests they are in grave danger.
Global populations of reindeer (also known as caribou) have already tumbled by two-thirds over the past three decades. Which is what prompted a team of researchers from Denmark, the United States, and Australia to try to map out what the future looks like. Using a wide range of data on population and geographic range dynamics across 21,000 years—including fossil records, ancient DNA, records of human migration, as well as paleo and historical climate reconstructions and climate projections—the team created maps of where reindeer might be able to survive in the future.
The changes in the environment due to climate change are wreaking havoc on them.
These maps suggest that reindeer populations could decline by up to 80 percent in some parts of the world between today and 2100. “Unfortunately, some of these caribou populations will suffer quite a lot from future climate change, whether it is from a middle of the road scenario or a worse worst-case scenario,” says Elisabetta Canteri, an ecologist from the University of Adelaide and University of Copenhagen, who led the work. The paper is published in the journal Science Advances.
North American populations seem to be in particular peril, due to more limited areas of suitable land and greater predicted changes in land use on the continent than in Europe or Asia, says Canteri. This means that reindeer populations that find themselves in trouble will have a harder time finding new territories to which they can migrate.
Reindeer population declines could be devastating not just for the reindeer but also for the plants, animals, and human communities that depend on them. Reindeer and caribou eat small saplings, which helps to keep forests from overgrowing, and crowding out other species of flora, which in turn, helps to mitigate climate warming. They are also an important species for Indigenous communities—who use the animals for transportation and food, their antlers and bones for tools, and their fur for clothing. The animals are also symbolically important for Indigenous cultural identity. A die-off of some of these reindeer populations could be “really stressful” for the people that depend on them, says Canteri.
Reindeer evolved around 21,000 years ago at the last glacial maximum—and they have survived other past episodes of rapid warming, says Damien Fordham, an ecologist at Australia’s University of Adelaide who co-authored the research. But today, temperature changes are compounded by other human-driven threats and already depleted population numbers. “With global populations already reduced by nearly two-thirds in just three decades, further losses of reindeer and caribou will destabilize tundra biodiversity, diminish carbon storage, and intensify climate feedbacks.”
The animals are uniquely adapted to a set of colder, drier conditions—and the changes in the environment due to climate change are wreaking havoc on them. Summer heat stress, which occurs more often with climate change, can cause them to stop eating to avoid overheating, says Eric Post, an ecologist at the University of California, Davis, who co-authored the research. “When they shut down, they don’t eat, and that means they go into winter with less body mass,” he says.
Additionally, winter warm spells melt the top layer of snow, which then re-freezes when it gets cold again, creating an ice layer that can be difficult or impossible for caribou to dig through to find food. Mass starvations can result. “Add to these other factors like disease, parasites, human encroachment, and other forms of habitat loss and you’re looking at climate change as a threat multiplier,” says Post.
Reindeer that find themselves in trouble will have a harder time finding new territories.
Elie Gurarie, an environmental biologist at SUNY’s College of Environmental Science and Forestry who was not involved in the new research, says the new research is an “innovative, very big picture look at the drivers of caribou and reindeer populations since the last ice age combining a dizzying range of data types.”
There is still a large amount of uncertainty in the models, however, says Gurarie. “Caribou populations fluctuate dramatically over multi-decadal cycles, and despite a century of intensive Western scientific research, and many, many generations of lived experiences by the Indigenous people of North America and Eurasia, the ultimate causes of those fluctuations are very poorly understood.”
He adds that in addition to climate change, caribou are facing unprecedented pressures from industrial development—including roads and ports—across the Arctic. “That kind of development threatens to undermine that very superpower which has allowed them to thrive: their large-scale mobility and ability to range-shift, or disperse.”
Anne Gunn, an independent expert who worked with the government of the Northwest Territories as a field biologist, says that collectively, scientists know less about the conservation status and landscape changes in Russia—so she says that context should be a priority for research rather than North America.
For Canteri, hints about the future always lie in the past. “The past can really be good for informing for the future,” she says. “Having continuity from past to future will be very important for conservation measures and for better predicting what will happen to species.”
As their numbers dwindle, the regal reindeer may become an increasingly uncommon sight in the far north—a callback to much older, colder times. 
Lead image: zaclaharia / Shutterstock
