Dr. Nancy Langston, Michigan Technological University
In May 2018, woodland caribou (Rangifer tarandus caribou) were declared functionally extinct in the United States. The last remnant population in the Selkirks Mountains of Idaho dwindled to three lone females. In the Lake Superior basin, a genetically distinct population of woodland caribou nearly met the same fate in February 2018. Populations in Quebec, Newfoundland, and Alberta are dwindling as well. Across the Canadian north, woodland caribou have disappeared from roughly half their 19th century range. Is climate change dooming woodland caribou? Or are managers using climate change as an excuse to avoid making difficult policy decisions that could save the caribou but antagonize industry and environmental groups?
Woodland caribou are part of the globally-distributed species Rangifer tarandus, which includes reindeer in Eurasia, barren ground caribou across the North American Arctic, and woodland caribou in the boreal subarctic. Members of the Cervidae genus, which includes deer, elk, and moose, caribou thrive in a variety of habitats. They are a migratory species that can cover vast distances—or adapt to much shorter migrations. Barren ground caribou and Eurasian reindeer are famous for migrations covering more than a thousand kilometers, while Lake Superior woodland caribou have shorter movements from wintering to calving ranges.
One of the few large megafauna species to expand rather than go extinct in the Late Pleistocene, caribou survived repeated glaciations by moving to ice-free refugia. Boreal woodland caribou found refuge in the Appalachian mountains, while Eurasian reindeer moved to what’s now Italy, France, and Spain. Each time the ice retreated in an interglacial period, caribou followed the melting ice north, expanding into new habitats across a diverse, warming landscape.
At least 10,000 years ago, people began following caribou on their journeys north, and a striking diversity of human-caribou relationships developed across the north. In Siberia and Mongolia, Indigenous peoples fully domesticated reindeer, creating close spiritual and material relationships with them. In Sápmi (northern Finland, Sweden, and Norway), the Sami people continued to hunt rather than domesticate reindeer well into the 16th century AD (Langston, 2014). But when Europeans colonized Sápmi for mineral, forest, and agricultural resources, wild reindeer populations declined as the Sami and Europeans began hunting them past their ability to reproduce.
The Sami developed a semi-domesticated relationship with reindeer to protect their remaining populations, shepherding them on their long migrations but never fully taming them as beasts of burden. By contrast, North American caribou remain wild, and Indigenous peoples have not domesticated or tamed them. Yet the two species, humans and caribou, have developed extraordinarily close material and spiritual relationships across North America. For example, Gwich’in leader Sarah James said, “The Gwich’in are caribou people” who believe that “a bit of human heart is in every caribou, and that a bit of caribou is in every person.” (Gwich’in Steering Committee, 2005) According to anthropologist Piers Vitebsky, caribou have made human life across the Arctic possible as climates changed in the Late Pleistocene, allowing people to thrive in ecosystems that would otherwise have been uninhabitable (Vitebsky 2005).
In the Lake Superior basin, a genetically distinct population of woodland caribou developed, ranging as far south as the Lower Peninsula of Michigan and as far north to Hudson’s Bay in Canada (see Map 1 above). Never particularly abundant in any place other than wolf-free islands—for low caribou numbers helped keep wolf populations low—woodland caribou were widespread across the northern forest. They flee from predators or find refugia in deep snow, windswept barrens, dense bogs, or rocky coastlines, where wolves falter. Predator avoidance was a strategy that served woodland caribou well in North America for over a million years, but now they are vulnerable to predation if their migration routes are cut off by development, or if predator populations increase with human disturbance. And many forms of human activity do increase predation. Railroads, logging roads, forest conversions, and wetland drainage have offered easy access for human and canid predators. White tailed deer have expanded their range into caribou territory, for the edge habitat left by forestry serves them well. Deer in turn invite higher wolf populations, while also spreading a parasitic brain worm that kills caribou but not deer.
In 1850, the last woodland caribou vanished from Wisconsin. By 1912, caribou were gone from mainland Michigan. By 1928, the woodland caribou of Isle Royale in Lake Superior were extirpated (Dybas 2015). Minnesota caribou persisted for longer because vast bog and fen complexes provided refuges from hunting pressure and wolf predation. Wildlife managers tried hard to protect caribou in Minnesota, establishing the Red Lake game reserve in the early 1930s and resettling failed homesteaders and blocking their drainage ditches to restore bog habitat (G. D. Racey and Armstrong 2000).
Still, by 1937 the last native band of woodland caribou in the bog area had dwindled to three cows in the Big Bog muskeg between Red Lake and Lake of the Woods. Farming and hydropower development along the Rainy River sliced off their traditional migration route between their calving grounds in Ontario and wintering habitat in Minnesota. Biologists translocated caribou from Saskatchewan to the Minnesota population starting in 1938, but without a connection to the Canadian calving ground, the population could not sustain itself (Bergerud and Mercer 1989; Manweiler 1938, 1941). Two individuals straggled down Minnesota’s rocky coastline near the Canadian border during the winter of 1980-1981. One was probably hit by a car and the other's fate is unknown.
Recent range of Lake Superior woodland caribou. Currently, only small populations persit on Michipicoten Island southwest of Wawa Ontario and the Slate Islands sound of Terrace Bay. Note the discontinuous range between the Lake Superior population and the more northern populations. Credit: Ontario Ministry of Natural Resources and Forestry.
In the United States, woodland caribou are now a ghost species persisting only in place names and memories. Ontario’s population of woodland caribou have fared better, yet they too have retreated from most of Lake Superior. From 1880 to 1990, the “extinction of caribou crept northward at a rate of 34 kilometers per decade,” (Badiou and et al., 2011). By 1912, the Lake Superior woodland caribou had been hunted out from the western shore and Thunder Bay region. In the Lake Nipigon watershed just north of Lake Superior, caribou thrived until the Canadian National Railway came through in 1910, and then that population dwindled. Along the north central and north eastern shores of Lake Superior, woodland caribou range had remained continuous all the way north to Hudson’s Bay. But after World War II, mineral, forest, and energy development fragmented their range, and caribou populations became discontinuous, with the Lake Superior population cut off from the more northern populations. This wasn’t a northwards migration, with caribou expanding into new territory. Rather, it was a cascade of local extinctions driven by hunting, predation, and habitat loss.
Well into the 2000s, Lake Superior woodland caribou seemed to be hanging on. Populations persisted in Pukaskwa National Park and on refugia in the Slate Islands and Michipicoten Island. When wolves were absent, woodland caribou populations were able to increase exponentially. In the early 1980s, Gord Eason and other biologists translocated 9 caribou from the overpopulated Slate Islands to then wolf-free Michipicoten Island, and by 2012, the population had grown to nearly 1000 individuals. On the much smaller Slate Islands, free from predators, caribou populations may have risen to as many as 600 individuals.
Wolves crossed ice bridges in the cold winter of 2013-2014, making their way onto the last two island refugia—Michipicoten Island 16 km off the coast, near Wawa Canada, and the Slate Islands group, about 12 km off the coast near Terrace Bay. Within two years, the population of perhaps 1600 caribou crashed to a couple dozen individuals on Michipicoten Island and several lone males on the Slates. In January 2018, biologists calculated that the entire Lake Superior woodland caribou population might have, at best, two more weeks left on earth before it went extinction.
Soon after wolves appeared on the islands in 2014, an informal coalition of the Michipicoten First Nations Community, local cottagers, and caribou biologists had begun petitioning the Ministry to protect the Lake Superior caribou from extinction. Options included culling the island wolves (unpopular with environmentalists) or moving wolves to Isle Royale in Michigan, where the US National Park service had been spending years trying to decide whether to restore them. Alternatively, if wolf control was impossible, then caribou could once again be translocated to wolf-free islands.
The Ministry, however, refused to act. In public, their biologists insisted that watching predation play out would be an interesting scientific experiment. Let natural processes find an equilibrium, one Ministry biologist suggested. In private memos that the caribou advocates obtained through Freedom of Information Requests, ministry personnel suggested that they expected extinction and were unwilling to expend resources to prevent it.
After an international media campaign that caught the attention of the New York Times, the Globe and Mail, and numerous regional media sources, the Ministry finally agreed to act. In three dramatic interventions, biologists captured caribou in large nets and helicoptered them over to wolf-free islands. Several were taken back to the Slates archipelago, where wolves had vanished after eating most of the caribou, and others to Caribou Island 35 km south of Michipicoten Island.
So far, most of the caribou seemed to have survived the translocations. Calf tracks were found on a beach on the Slates this summer. Perhaps the population won’t face extinction just yet; perhaps woodland caribou won’t completely be extirpated from the Great Lakes region.
Why was the Ministry so slow to respond? Local resident Christian Schroeder, an advocate for translocation, suspected that many biologists and policymakers within the Ministry share a perception with environmental NGOs that climate change will inevitably doom the caribou. “Caribou in Canada may be doomed by climate change and habitat loss” proclaimed one headline in Nature World News on Dec. 16, 2013 (Foley 2013). A scientific paper in Rangifer projected “complete loss of woodland caribou in Ontario if winter temperatures increase by more than 5.6º C by 2070,”(Masood et al. 2017). If caribou really are doomed by warming in the Anthropocene, expending significant resources to save them might seem a waste of money and effort.
Leo Lepiano, lands and resources consultation coordinator for the Michipicoten First Nation, notes that if the caribou vanish, many management dilemmas for the Ministry vanish as well. Currently, development in woodland caribou range cannot exceed 35% of the landscape. That limit would be lifted for the so-called “discontinuous range” between Lake Superior and the northern populations in if Lake Superior caribou died. More of the boreal forest could be opened to transmission line development, intensive forestry, and Ring of Fire mining expansion.
If woodland caribou really are doomed by climate change, why expend resources and slow development save the last few? In fact, caribou, given half a chance, may be far less vulnerable to climate change than other northern species. Physiologically, unlike moose that cannot forage well as temperatures warm, woodland caribou don’t experience thermal stress—at least not in the range of temperatures predicted for Lake Superior. Moose begin to experience thermal stress at 14ºC, with open-mouthed panting and reduced foraging. Caribou, however, don’t show measurable physiological responses until temperatures skyrocket to 35ºC (Racey 2005, Yousef and Luick 1975).
Popular perception holds that wintering woodland caribou require old growth boreal forest with abundant lichens. Such forest types are unlikely to persist along much of Lake Superior in a warming climate. But while caribou select lichens in winter if they’re available, they readily adapt to other habitats as well. Michipicoten Island, for example, has a Laurentian mixed forest dominated by hardwoods, and caribou thrive there in the absence of wolves.
Caribou responses to historical climate change offer clues to how caribou might respond now. At the end of the last glacial maximum, the fossil record shows that caribou vanished from their warming refugia. Some anthropologists interpret this climate history as evidence of the profound vulnerability of caribou to future climate change (Grayson and Delpech 2005). But this interpretation reduces the agency of caribou themselves. Post-glacial caribou didn’t simply go extinct (as they later did in the 20th century Lake Superior range reductions). Rather, caribou chased the melting ice north, exploring new environments that were opening up as the climate warmed and expanding their range across the circumpolar north. North American caribou populations actually expanded in size at the end of the Pleistocene, as other Pleistocene megafauna (with the exception of brown bear and tundra muskox) went extinct. Migration was central to caribou post-Pleistocene resiliency, suggesting that they can be resilient if their habitats are connected (Mann et al. 2015).
Americans typically imagine caribou as creatures of distant wilderness, a remnant of primeval nature that was irrevocably lost to industrialization. Woodland caribou, in this discourse, need vast, untouched wilderness and will be doomed by climate change and the Anthropocene. These beliefs are powerful, but they are flawed—and they let agencies avoid taking pragmatic actions today to restore woodland caribou. There’s nothing inevitable or mysterious about the demise of woodland caribou. Specific policy decisions led to their declines in the 20th century, and reversing those policy decisions has the potential to lead to their rebound, but not if we continue imagining woodland caribou as creatures of an untouched primeval forest.
Current rhetoric about woodland caribou mirrors the rhetoric of early conservationists in the late 19th century. As Teddy Roosevelt wrote in 1902, “it would seem the race must become extinct in a comparatively brief period” (pg. 39). When agencies and NGOs talk about woodland caribou as too vulnerable to be sustained in the Anthropocene, it becomes a self-fulfilling prophecy. Agencies and environmental groups become reluctant to restore them, for that suggests continuing care, a need to keep investing time, resources, and energy to manage predators and migration routes. For woodland caribou to thrive, we need to rethink assumptions about the need for continuing human stewardship of migratory wildlife in a warming world.
Caribou will indeed dwindle in a warming world if we restrict their migrations and refuse to manage their predators. But climate change should not be an excuse to give up on the management strategies here and now that could keep them from extinction. Climate change isn’t going to doom woodland caribou. Human policy decisions, however, might.
Nancy Langston is Distinguished Professor of Environmental History at Michigan Technological University. Her most recent book is Sustaining Lake Superior: An Extraordinary Lake in a Changing World (Yale 2017). She is currently working on an environmental history of woodland caribou and common loons in the Anthropocene.
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