• Map: Sam Herold/Canadian Geographic

THE BIG LAKE GLITTERS in the sun. A blue butterfly floats above a sand dune. I clamber to the top and look down at a white pond half enclosed by low willows. But this pond has no water in it. What turns the land white are thousands of cottongrass tufts — a shining illusion in a subarctic desert, and a scene that would have delighted Monet.

Of all the places I’ve travelled in Canada, the sand dunes that extend for about 100 kilometres along Lake Athabasca in the northwestern corner of Saskatchewan have to be the most surprising. They are the most northerly expanse of active dunes in the world, spreading across more than 30,000 hectares and containing an extraordinary array of wildlife. Nine varieties of plants, including four full species, exist nowhere else in the world. In 1992, the government of Saskatchewan designated much of the region as Athabasca Sand Dunes Provincial Wilderness Park.

Provincial parks don’t always get their due in Canada. Our most famous parks are national parks, many, such as Banff and Jasper, known throughout this country and far beyond. But with the exception of Algonquin in central Ontario — a park whose size, long history and association with the Group of Seven painters give it almost iconic status — most Canadians would be hard-pressed to name a single provincial park outside the province where they live. And that’s a shame. The unique plants that have evolved along the south shore of Lake Athabasca — endemics, to use the scientific term — make these constantly migrating dunes a biological treasure.

A fragile one, too. From the perspective of a felt-leaf willow or a floccose tansy, it’s fortunate that the dunes are hard for people to reach. They received more traffic in the early 1980s, when Uranium City, Sask., just north of Lake Athabasca, had a population of nearly 5,000. Today fewer than 100 people live there. Most visitors now enter the park by float plane. I arrived in an orange-and-white Cessna 185 accompanied by a guide, Tim Wintoniw of Churchill River Outfitters. Our two-and-a-half hour flight starts in the little town of Missinipe, a gateway to the many fly-in fishing camps of northern Saskatchewan.

Our pilot, Les Wilson, takes off at 4:35 a.m., the red sun of late July barely breaking the horizon. Until the sun climbs, the lakes below us remain draped in mist. Peering down, I find it hard to tell if we’re passing over land striped with water or water ribboned by land. I try to count the lakes in view, and give up at 200. On one, an islet shaped like a fish hook holds a single tree.

As we leave the interlaced Churchill River system behind, the bones of the land begin to jut through the forest. Trees become skimpier. Blackened expanses show the brute force of fire. Beyond lies Lake Athabasca — the fourth biggest lake whose waters are entirely within Canada, and the 20th by size in the world.

Wilson passes me a set of headphones. Without them, conversation inside the noisy cabin is almost impossible. He insisted on leaving Missinipe early because of the waves that agitate Lake Athabasca when the wind gets up. On large bodies of water, early morning is often the only time a float plane can safely land. “When I flew here before,” he says with a grin, “we bounced.”

Not this time. Wilson manoevres the plane above the sinuous course of the William River, its dark water braided with butterscotch swirls of sand as it prepares to empty into Lake Athabasca. The river splits a dramatic landscape: above one bank is the dark green of a boreal forest, above the other the pale yellow of a desert. Even by 7:15 a.m., a few whitecaps have risen on the lake as the Cessna turns and banks. But Wilson brings us smoothly down.

As Wintoniw helps him refuel for the return flight, I wander around the beach near our landing site. Fresh tracks along the shoreline show where a wolf has padded by. Among the lichen a few dozen metres inland lies a pile of moose scat. An osprey passes overhead. A small plover skitters down the shore. After the plane has taken off again, the only sound is a light breeze, the only evidence of human beings our footprints in the sand.

PEOPLE HAVE BEEN LEAVING footprints in the area and using its resources for at least 7,000 years. Archaeologists say that the Northern Plano were the earliest, followed by the Shield Archaic, the Taltheilei and their descendants, the Dene. Today there are Dene reserves near Fond du Lac, Sask., at the eastern edge of the lake, and Fort Chipewyan, Alta., at the far southwest. Hunters and fishermen from these communities still travel through the region.

“A lot of artifacts in the dunes could be either buried or exposed because of the wind,” says Bryan Gordon, an archaeologist at the Canadian Museum of Civilization who has studied the long history of human presence in the area. “It’s the luck of the draw. Many of the sites are in sand blowouts. Who knows what’s beneath the surface?” On one research trip, he and a graduate student had their camp ransacked by a black bear who succeeded in opening — and consuming — an entire bottle of sherry.

The dunes dominate a landscape still being moulded by wind. It took shape when the glaciers fell back after the last Ice Age, exposing an underlying sandstone formation. Lake Athabasca’s water level is lower now, and the area it covers is smaller than it was than a few thousand years ago. The emerging ridges and sandhills were quickly colonized by plants.

For them, sand is a mixed blessing. It gives their roots more room to grow than does the scanty, rockbound soil of the subarctic forest. But the sand is mobile, at the wind’s mercy, and when it shifts, roots get exposed. Within a few years, a healthy tree can turn into an aerial sculpture ready to tumble. Many plants that thrive here can regenerate their roots from underground stems, allowing them to survive burial by sand.

The flora of Lake Athabasca has evolved with amazing speed. Other regions of Canada that are rich in endemic plants are larger: the Queen Charlotte Islands in British Columbia, the unglaciated areas of central Yukon, and Quebec’s Lower St. Lawrence. Because of their limited range, nearly all the Athabasca endemics now appear on the watchlist of the Committee on the Status of Endangered Wildlife in Canada. The rarest of them — a plant whose dense spray of stems spreads out from a single taproot — has the wonderful name “impoverished pinweed.”

Yet as Wintoniw and I hike over the dunes and past the delicate gravel pavements, we see that many of the endemics are common and easy to find. The stem and leaves of Athabasca thrift are beautifully adapted to retaining moisture; the thin, flexible stem of sand stitchwort enables the plant to bend easily and resist the force of windblown gravel.

Although the July sun is hot, the sand feels cool beneath our feet. I carry my sandals most of the way. Wandering the dunes, I become a connoisseur of sand: its textures, its colours, its moisture levels. Wintoniw and I say little as we walk. But over the breakfasts and dinners he prepares on a small propane burner, we talk at length.

He grew up in a devoutly Christian family in rural Manitoba, and has never lost his faith. To me the endemic plants offer vibrant proof of natural selection. Wintoniw draws a different conclusion: “The value for me is in seeing just how incredible nature is. The trees survive here, windblown, sandblasted, in the most difficult conditions. It lets me know how wonderful and amazing God is.”

ONE EVENING Wintoniw and I are dining on rehydrated apricot and cashew curry when a movement in the underbrush catches my eye. A black bear is prowling around our campsite. Wintoniw walks calmly in the bear’s direction, making a racket. The bear retreats. But when we get up the next morning, fresh tracks indicate it has paid a second visit. We load our backpacks and move to another site. The mosquitoes are ferocious but the bear is absent.

Our last campsite is farther east, near a small lake inland from Lake Athabasca, a short hike through a burnt-out forest. In case of poor weather, Wilson could bring down the Cessna here even if waves on the big lake made a landing impossible. As Wintoniw and I hike to the final campsite, three canoes pass us. The six people in them — visitors from Lethbridge, Alta. — have reached the area in a float plane big enough to carry their boats, and have canoed down the William River to Lake Athabasca. Except for a few fishermen in a distant motorboat, they are the only humans we see during our four days in the park.

Setting up the final camp, we notice a bald eagle keeping watch on us from atop a nearby spruce. It takes a while before we realize why: a dozen trees over from the sentinel bird is a large nest with two scraggly, black-feathered eaglets inside.

Southerners can’t reach the park without flying part or all of the way. Could the eagles, ospreys, wolves and endemic plants continue to flourish if it were easier to visit? “It’s trying to find the right balance,” Wintoniw responds when I ask his opinion. “We’re lucky to have had the chance to see nature acting on its own here, without human influence. If you open the park up to lots more visitors, that sense would disappear.”

But even on a shore so apparently pristine, we’ve noticed plastic bottles, broken glass, styrofoam, fish hooks, sheets of plywood and chunks of metal. More worrying, the lake is fed by the Athabasca River — which means it lies downstream from the massive oil-sands projects in northern Alberta. Since 1970, the amount of water flowing through the river has dropped considerably. What impact all this will have on the wildlife in and around Lake Athabasca remains unclear.

For the moment, the park remains a place of tranquil grandeur. It’s a calm morning and we are still sipping coffee, listening to a loon’s distant cries, when a low hum in the sky alerts us to Wilson’s return. He lands on Lake Athabasca and taxis to shore. When we’ve loaded the plane, I jump aboard with a full heart. Our footprints will soon be gone. As the Cessna regains the sky, I peer down and see an eagle keeping vigil in its spruce.