How long did I walk in the footsteps of the bear? It was a warm day, 20 years ago and 80 miles north of the Arctic Circle, the sky translucent blue behind low mountains. The tundra, just starting to turn autumn crimson and saffron, held all my attention. Eventually, I looked down at the trail. And there: the ovoid front paw prints, claws puncturing a constellation into the mud inches above each toe, trailed by back feet as long as two hand spans. Grizzly. Next to them, indentations from my boots. Both filling slowly with water.

The clock of the morning’s rain put the bear at five, maybe 10 minutes ahead, invisible where the trail turned among willow brambles. For half a moment, I wondered at the tracks—this grizzly must weigh 700 pounds, maybe 800. Then another calculation: How many feet between myself and the bear? Thirty? Twenty. A hot wire uncoiled below my ribs, a jolt of fear so pure it tasted like metal.

I had been in the Arctic for two days when that bear chose not to turn on the trail and end me with a swat of his paw. Because of his decision—it was a male, I am guessing, from the size—I was alive to spend the next two years living in his territory. I was never again stupid enough to go walking alone and unarmed in autumn. But the moment with the grizzly, unseen yet so present, was not the last spark of that particular and striking kind of fear, the fear of an animal or circumstance bursting through my impression of being an isolated, sovereign human self. I thought, too, that fear was purely negative, a sensation without value. The bush had other plans: Those grizzly prints were the first lesson on a syllabus that would reshape how I imagined the human relationship with the world at large.

“Bush” is what people in the English-speaking Arctic call the territory away from town. I was in the north to train sled dogs, which meant that, as winter covered autumn’s colors on the tundra, I and a team of eight or 10 dogs were constantly in the bush.

As an 18-year-old from Iowa, I had everything to learn: how to harness dogs so eager to run that they were barking, leaping, wriggling blurs, incorrigible with glee. How to tie a proper knot. Where to find dry branches for a quick fire. How to walk with snowshoes and not fall every third step. Some frustrations—as when one dog chewed through her harness while I, bent over and sweating, struggled to get another ready—made me weep. It was a rare day when I was not sore. My biceps grew so quickly from wrestling dogs and sleds and frozen 40-pound salmon to feed my team that my pinky and ring fingers went numb, the nerves pinched by new muscle. But the pain and irritation of incompetence distracted me from a homesickness so profound, I imagined it walked beside me, a lumbering dark presence. I woke every morning cloaked in its despair.

Gradually, as the dogs became stronger and I less likely to die from my own inexperience, we mushed farther from town. It was in the bush, usually with dogs and usually without other people, that I learned how to navigate by memorizing the bends in rivers or the angle of a hillside, and how to read the gestures of my team for tiredness or excitement. I came to know the dogs as individuals, with likes and strengths and quirks, and they began to trust me, the leaders listening when I asked them to turn right or left, the whole group howling and running in circles of joy at the sight of a harness. As a team, our trips went from 10 miles to 30 to 70. Each run submerged us deep in the beauty of the open country, the wide skies and hills that, covered in snow, were 10,000 shades of white and gray and crystalline blue. The homesickness began to fade—or rather, the bush began to feel like home.

But it was a home struck through with fear. Take the afternoon one February or March—late enough in the winter that the days had hours of light in them again—when I rounded a bend in the river, the dogs going steady, only to see a cow moose 20 or 30 yards ahead. I knew enough by then for the fear to take no calculation: A bull can weigh 1,500 pounds, a cow nearly 1,000. Large enough that, faced with wolves, moose will either flee or trample their canine attackers. To a moose, my dog team was indistinguishable from a wolf pack.

So she charged. The distance between her hooves and my lead dogs diminished in a spray of snow. The dogs, filled with hunting drive and beyond entreaty from me, bolted to meet her. I could see the white of the moose’s eye, her head rearing back, her breath steaming in the cold air. Twenty feet, then 10. She had the pivotal choice: to stamp into my team, and into me, or to turn.

I can write this because she turned. It was one of many such Arctic reckonings. Cumulatively, they wore away at the assumptions I was born into, of culture and climate, where imagining human life as separate from the environment was not just possible but normal. Natural history and human history, after all, are taught in formal classrooms as distinct realms. But moments of danger taught me that I was far from autonomous. My existence depended not just on my actions, but on those of a bear, or even on a sudden blizzard that, if ignored, would bring storm-blindness and hypothermia. This fear was guidance—to not swagger into bear country—and also a kind of communication, a way for living things and circumstances outside spoken human language to assert their importance. In the Arctic, the moose, turning in the last moment of her lunge, gave notice of my contingency. You exist today because some other being has willed it so.

I came to think of these moments of exigency as “bush fear,” which undid my delusions of wilderness as beautiful but essentially passive. The bush spoke in many ways, from the hoarse calls of ravens announcing a carcass to the northward turn of the wind before a storm. Fear was a particularly vital mode of speech, not debilitating but instructive. It was part of what made the bush home, by shocking me into a relationship with the place.

A primary lesson of bush fear: I was only one among many things pushing their will into the world. It carried a moral edge, offering up the necessity of thinking beyond the confines of the self. And it was an active emotion, exploding in moments when no one being, human or otherwise, had complete power. It felt like the opposite of homesick despair. And sometimes, as in learning when not to go alone into bear country, it was a charge to alter my actions in order to live.

Earlier this year, 20 years after I breathlessly crept away from the unseen bear, I was back, visiting the grizzly’s territory. Somewhere, his grandcubs were sweeping blueberries off the hedges with purpled lips. I did not see them, or even their tracks; staying clear of grizzly haunts meant that I did not need to calculate the feet between myself and peril.

Except that there were so many calculations. It was a fearsome season across the north. The Arctic had never been hotter in recorded history. Ice was gone from the Bering Sea months early, and on the tundra I knew so well from years on a dogsled, the uncanny warmth also left its mark. Here, a lake gone, drained in a matter of days after the permafrost holding one bank loosened under the sun. There, spruces leaning in ashy gray clusters, killed as their roots pulled free of soil that had lost its lining of ice. Everywhere, the willows and alders and birch ominously verdant, building walls of brush impenetrable to caribou and likely to become tinder with a drought.

On the day I arrived north of the Arctic Circle, the Greenland ice sheet lost 11 billion tons of surface ice; the changes on the tundra, if smaller in scale, were harder to abstract. I spent most of a week along curling Arctic rivers. Bend after bend, the southeastern slopes were sloughing tons of dirt and trees into the water, the form of the land changing not over centuries but over months.

All these signs put time to action: How many years ahead is the peril? Twenty? Ten. They are the tracks of fear, scaled up, past being warning of personal harm. The eroding hills spell out danger at geological magnitude. Watching the transforming landscape as it slid past, I felt the familiar adrenal lurch of watching something—here, the very shape of the Earth—in dangerous motion.

In this year of hurricanes that raze the Bahamas, of heat waves in Europe, of wildfire dread in California, of unplantable fields in the Midwest, it is not necessary to be in the Arctic to be afraid. But what to do with this fear, both familiar and new, in its tremendous scale? The close instances of fear that schooled my first Arctic years taught me two things: Pay attention, and do not provoke. Do not give the bear reason to attack. Do not give the blizzard reason to kill you. Fear taught me down to the very sinew that human actions exist in relation to the larger world. Burning fossil fuels at the current rate is a massive, continuous, accelerating provocation. And rather than retreating, humbled, we are collectively charging into the bush after the bear.

Except that we obscures who is deciding to charge. Not only are wildfires and drained lakes the product of fossil fuels burned disproportionately in the United States and other nations early to industry; they are the result of choices made by a tiny fraction of those countries’ citizens. American, British, and Brazilian leaders—to mention an obvious few—actively work against learning from the fearful impacts of climate change. In the face of obvious danger, they offer denial, or despair.

Once, the runner of my sled caught on a piece of ice jutting from the frozen river and flipped me on my back in a breathless heap. The dogs kept running; I was new to them at the time, not yet integral to their lives, and they knew home was just five or so miles away, and with it dinner. It was dark, but the Arctic night was luminous where the snow reflected the starlight and green smolder of the northern lights. It was 20 degrees below zero, probably. And there I was, alone in the deep quiet, with a long walk ahead in my 40 pounds of parka and boots. I was annoyed—I also wanted dinner—until out from the glimmering dim came a wolf howl, answered shortly by a second, and a third. They were not far. The cold gasp, then, as I realized that of course I was not alone.

I learned in the Arctic that fear is catalytic. The night I fell off my dogsled, the sound of the wolves followed me for dark miles. Fear, and with it a seething need to survive, kept me moving. It was no time to sit down alone in the cold dark and blindly await what might follow those howls. Nor is there time now, even as a kind of apocalyptic despair has become, for some, an attractive posture.

“I want you to feel the fear I feel every day,” Greta Thunberg pleaded at Davos in January. And I agree. Despair is a homeless feeling. Fear forces us to recognize the terms of being alive in our actual home, in a world that we can rouse but never master. It is a call to alter human action, to demand a different politics, and, by doing so, to live.