A stiff wind buffeted the helicopter as it set down near the gravel shore of Wrangel Island, a remote spot of land 300 miles north of the Arctic Circle in Russia’s extreme Far East. After flying two and a half hours from Pevek, Russia, mostly over open water, the aircraft smelled of vodka and gasoline from the extra fuel cans secured inside. Joel Berger peered up at the white hills that rose around him and spotted several black flecks on the slopes: his quarry, muskoxen.

These shaggy, horned creatures are one of the many archetypal Arctic species that thrive on Wrangel Island, a little-known hotspot for polar biodiversity. Berger, a wildlife biologist at Colorado State University, came to Wrangel as part of a joint Russian-American project to understand how climate change and other factors, such as predation by polar bears, might be affecting the island’s roughly 900 muskoxen. The island’s isolation, along with its cold, dry polar climate, have created a unique and surprisingly biodiverse ecosystem. Despite the harsh conditions, more than 400 varieties of plants persist here—twice the number found on any other similarly sized piece of Arctic tundra—as well as hundreds of mosses and lichens. Some of them are not found anywhere else on Earth.

“Wrangel Island is wild nature at its best,” Berger says. “It’s spectacular.” At 7,600 square kilometers (2,900 square miles), the island is roughly the size of Yellowstone National Park. Its low, rounded mountains are arranged in ridges like a corrugated tin roof, and its wide coastal plains spill into the Arctic Ocean. The island is criss-crossed by reindeer, scavenged by wolverines, and patrolled by perky Arctic foxes. Thousands of Pacific walruses loll across its gravelly spits. Countless birds cling to the island’s rocky cliffs and nest along its riverbanks, including horned puffins, black guillemots, Pacific loons, and endangered peregrine falcons. It is home to the only breeding colony of snow geese in Asia and is one of the densest nesting areas for snowy owls. But the island is perhaps best known for its polar bears, especially the scores of female bears that den and give birth in the island’s snowy foothills each winter.

Wrangel Island was named after a 19th century Russian explorer who inferred its existence by observing seasonal bird migrations and listening to stories from indigenous people in northeastern Siberia. Today, the island and its surrounding waters are classified as a zapovednik—the highest level of environmental protection afforded by the Russian government—as well as a UNESCO World Heritage site. These designations are a testament to the island’s rich diversity of plant and animal life, some of which found its way here thousands of years ago.

Unlike most of the northern hemisphere, Wrangel Island was not swept up in the transformations that came with the last ice age some 10,000 years ago. The island was never covered by thick glaciers, nor was it inundated when the global climate warmed and melted the ice. Instead, as sea levels rose, Wrangel Island became separated from the mainland and the two ecosystems diverged. Peat and sedges carpeted Wrangel, while grasslands spread across the mainland. That, paired with the fact that the island lay out of reach of humans, made it a refugium for woolly mammoths. A small population of mammoths—the world’s last—managed to hang on here for 6,000 more years, but inbreeding led to harmful genetic mutations until finally the species tumbled into extinction some 3,700 years ago. Mammoth bones and three-foot-long ivory tusks still jut out of the gravel of riverbeds across the island.

Between its remoteness and unique blend of flora and climatic conditions, Wrangel Island has become a destination for many Arctic animals. The island hosts more than a hundred migratory bird species and seven resident species of land mammals, some on the edge of extinction. But as the climate heats up again, this once-isolated area has also become more accessible, exposing it to more intensive human activities. Large cargo ships are cutting through the thinning sea ice along the Siberian coast; companies are exploring offshore oil and gas deposits; and Russia is beefing up its Arctic military bases. The question now is whether Wrangel will be transformed by these development pressures, as other parts of the Arctic have, or if it will be protected and continue to serve as a refugium for some of the Arctic’s most iconic animals.

Bouts of unusually warm winter weather events have been costly to the island’s muskoxen and reindeer, which feed on herby tundra, dwarf shrubs, and grasses. Freezing rain in the fall and winter encrusts the tundra and locks the animal’s food into “impenetrable ice,” Berger says. The island has seen three times more of these rain-on-snow events than Arctic Alaska has, and the contrast shows in the health of the muskoxen that live in these two ecosystems. Berger has found that the juvenile muskoxen on Wrangel are smaller than their Alaskan counterparts. “They’re kind of runty,” he says. When the young animals don’t get the nutrients they need, they grow more slowly both in the womb before they’re born and in their first years of life.

Wrangel Island’s reindeer have fared even worse as the climate has changed. One February, several years ago, temperatures soared above freezing and then plummeted, trapping the island’s plants beneath an unyielding layer of ice. The reindeer population was “catastrophically destroyed,” says Alexander Gruzdev, the director of the Wrangel Island State Nature Reserve. “It was crazy. When I found them, there were about 6,000 animals dead at once.”

In contrast, polar bears on the island appear to be doing relatively well, all things considered. Wrangel Island remains one of the main, concentrated denning sites in the Arctic. Similar sites in Churchill, Manitoba and on Norway’s Svalbard archipelago have been seeing fewer bears than in the past, because some years the sea ice forms too late—or not at all. The female bears are then forced to find alternate denning locations. “This is a dynamic system, so there will be good and bad years,” says Andrew Derocher, a polar bear biologist at the University of Edmonton. But it’s all “part of the longer-term decline.” The number of denning sites is falling.

The polar bears that live on the Chukchi Sea move between Alaska and Russia via sea ice. They stick with the ice as long as they can, says Karyn Rode, a wildlife biologist at the U.S. Geological Survey in Anchorage, but “the northerly drop-off point is going to be Wrangel.” As such, female bears now spend more time on Wrangel Island than they did just two decades ago. Rode recently tracked radio-collared female bears and found that twice as many bears came ashore during low sea ice conditions, and they stuck around for 30 days longer than in the past.

While they’re on the ice, polar bears live off of fatty seals they forage. Once they move onto land to den, the bears usually fast. But retreating ice floes have forced the bears onto land earlier, and for longer periods of time. The females can’t go without eating for such extended periods and still manage to reproduce successfully. Anecdotal evidence suggests the bears may be changing their diet accordingly, and scientists don’t know what impact this might have—for the bears or the ecosystem. In 2015 rangers on Wrangel watched a bear rush a group of walruses hauled out on the beach, seemingly to incite a stampede so that it could pick off the injured and the dead. Gruzdev says he has also seen polar bears scavenging muskoxen, reindeer, and whales, and has watched them dig out Arctic lemming burrows in search of the tiny rodents.

Aside from a shipwreck, a few polar expeditions, a military radar installation, and an abandoned Soviet attempt at settlement in the 20th century, the place has, for the most part, been occupied by only a handful of rangers and scientists since the turn of the 21st century. Today, about 500 tourists visit annually, most arriving on rubber dinghies from expedition cruise ships to catch sight of the polar bears, muskoxen, and vast bird colonies. Much of the draw for tourists comes from the fact that Wrangel Island (along with its diminutive neighbor, Herald Island) was declared a UNESCO World Heritage site in 2004, and is currently one of the Arctic’s most highly protected nature reserves.

But there is a growing permanent human presence on the island, too. The Russian government recently installed solar panels and a wind turbine to generate electricity for its scientific activities, and modernized its six guest houses. In the past few years, as Russia has expanded its military presence in the Arctic, Wrangel Island has gained a new radar array and medical complex. Several additional buildings are planned for this year, according to The Independent Barents Observer.

Russian military experts have called the installations necessary for Russia to protect its strategic and economic interests in the area, including oil and gas deposits, as well as control of the Northern Sea Route that spans the country’s Arctic coast and threads the narrow strait that separates Wrangel Island from mainland Russia. The Russian government has been developing—and promoting—the route in earnest, hoping to persuade shipping companies to travel between Asia and Europe along its coasts, instead of through the Suez Canal. Since melting sea ice has recently made the route more navigable without an icebreaker ship, taking this shortcut would, for example, reduce the distance between the Japanese port of Yokohama and London by more than 4,000 nautical miles. Despite the increased risks of navigating unpredictably icy waters, the Chinese government is keen to use the route, which it calls the “Ice Silk Road,” to cut the journey of its ships to Europe by up to 10 days.

There’s also the possibility that oil and gas companies may soon begin drilling along the wide continental shelf of the Chukchi Sea. Rosneft—a Russian government-owned oil company—and Exxon Mobil Corporation jointly acquired three lease blocks to the north and east of Wrangel Island in 2013. While the two companies have told the Alaska Dispatch News they would respect the state reserve’s boundaries, the 190,000-square kilometer lease area overlaps the reserve’s protected buffer zone.

Oil operations on the U.S. side of the Chukchi Sea also threaten the island. A risk assessment made by the Natural Resources Defence Council using computer models found that if an uncontrolled oil spill were to occur from a well off the northwest coast of Alaska, it would have a 20 percent chance of reaching Wrangel Island. Shell Oil Company has since abandoned its search for oil there, but future exploration remains a possibility. Although President Obama banned all future offshore oil and gas drilling in the U.S. waters of the Arctic Ocean in the final weeks of his term in 2016, President Trump has since signed an executive order to extend offshore oil and gas drilling in the Arctic.

In late September 2016, Perham, who then worked for the U.S. Fish and Wildlife Service, spent a month on the island. The goal was to help establish a U.S.-Russian research program to better understand the ecological importance of the island to the polar bears living within the Alaska-Chukotka region. “I was born and raised in Alaska, and I’ve seen some remote places there,” he says “but as we came over the coast, it hit me: This is the closest thing to the end of the Earth.”

Perham and his colleagues traversed 1,000 kilometers of the island by ATV in search of polar bears. By the end of the month, the team had counted 179 bears, almost all in what appeared to be good health, and more than a third of them in family groups. Polar bears are typically solitary animals; females, males, and cubs don’t mingle unless there’s food involved, such as an irresistible whale carcass. But one day, Perham came across a cluster of 11 bears dotted along a mountainside, their white fur contrasted against the dark, snowless ground. “They looked like Dall sheep,” he says. The scene surprised Perham. Polar bears don’t often venture into the mountains, and there was no food source in sight to explain their close proximity to one another. Their resilience, though, was unmistakable. Perham says, “Because there is no ice, they congregate, and they’re used to it.”