The Case of the Disappearing Rabbit

In the roadless, snow-muffled backcountry of northwestern Montana lies your best chance of ever seeing a wild Canada lynx. An improbable creature, it is small on the spectrum of wildcats—about three times the size of a house cat—and stands on disproportionately long legs, on which it is uncommonly fast. Its great head seems larger and wiser for its tuft of beard and the birdish plumes at the tips of its ears, but its feet spoil its air of gravitas. They are enormous. They act like snowshoes, and they are part of what makes the lynx supremely adapted to this part of the Rocky Mountains. Another inhabitant, the snowshoe hare, is adapted to life here, too. A lynx, if it could, would eat nothing but snowshoe hares its whole life, and pretty much does.

An animal so specialized that it only eats one kind of food has a tenuous place in the world. But this stretch of Montana—what the 19th-century naturalist George Grinnell named the Crown of the Continent—is unlike most places, or even most wildernesses. In an age of daily extinctions, the Crown has not lost any of the vertebrate species present when the first Europeans ventured this far west—creatures seen, heard, and feared by Lewis and Clark. If the Crown is a window into the past, it is also a particularly privileged window: no other intact ecosystem on the continent affords a view this grand. Only here do you find the full suite of North America's big predators—wolves, cougars, coyotes, and black and grizzly bears. Then there are the stranger beings: cutthroat trout, bull trout, and Arctic grayling in the glacial waters; river otter, bobcats, fishers, martens, lynxes, and wolverines. Between Glacier National Park and the Bob Marshall Wilderness Complex, the Crown is 10 million acres of the West as it once was, and as it would have been.

Yet it is not a time capsule. Being free from development by people hasn't made it a static place: the Crown rearranges itself, in a constant flux between the living and the dying, as the planet rolls on. Historically, this has happened on a time scale largely beyond our power of perception—"glacial pace" is not far from the mark. The problem is that glacial pace is not what it used to be. It is speeding up, as the glaciers melt into the Rockies, retreating up to 90 feet each year. For the first time in geological history, you can watch glacial ice move, and by the current projection, 20 years from now there will be nothing to see. Altogether, climate change is a phenomenon more keenly felt in a place like the Crown—a mountainous landscape with reservoirs of ice and snow—than anywhere else. This makes it the best possible natural laboratory, a window into the large-scale ecological change that global warming will bring. The effects of warming are magnified two to three times in the Crown, says Dan Fagre, climate ecologist in Glacier National Park, though the Crown's persistent biodiversity suggests that the ecosystem is weathering the difference so far. But Fagre thinks this persistence has a limit: at some point, the pressure of the changes will be too great, and beyond this unmarked boundary the present system will come apart. An ecosystem doesn't die, but as species depart or spread, it will change the way it operates, take a different form. Potentially, the Crown has innumerable thresholds—the last of the glaciers, the first animal extinction—beyond which it could rapidly become a fundamentally altered place: different trees, different cycles, different lives. Whatever will trip that invisible wire, a look now at the Crown is a look at final moments—the last of a storied American West, of the natural wealth that once enabled this extravagant diversity of life. What awaits, in a climate-changed world, is a new era of uniformity.

What sets the Crown apart from every other ecosystem on earth is its ecological schizophrenia. Straddling the Continental Divide, it is besieged by disparate climates from the fertile west, the open prairie to the east, and the cold north; even its rivers, issuing from Triple Divide Peak, flow in all four compass directions into the Pacific, the Atlantic, and the Arctic oceans. In all this, the mountains are the agents of volatility: they toss wind and snow to different sides of the Divide and wildly apportion sunlight to different slopes; historically, their dramatic nightly cooling has produced some of the coldest temperatures ever recorded below the Arctic. The convergence of these forces is what packs into the Crown the widest range of life on the continent, a diversity as distinctive as the tight profusion of Madagascar or the sweeping wealth of the Serengeti. "We have this incredible mix of microclimates," says University of Montana climate expert Steve Running, who shared the Nobel Peace Prize in 2007 with the Inter-governmental Panel on Climate Change, "which then allows an incredible mix of microhabitats for animals."

To a certain extent, this patchwork of habitats is its own refuge against ecological disturbance, which is why, though records of a warming trend go back to the 19th century, no population has yet abandoned the ecosystem. "The animals can make use of those gradients," Running explains. "They can go from the Pacific side over toward the continental side, they can walk from the southern end of the Rockies farther north, and then they walk up in elevation. When their habitat goes off the top of the mountain, then it's all over." Global warming has a leveling effect on mountains: under an atmosphere thick with carbon, mountains cool less, allowing lower-elevation plants and animals to push into the upper reaches. We get more of one kind of habitable world, but we lose the planet's extremes, along with their wholly unique strata of life—lynxes, for instance, and snow-colored hares.