Narwhals, one of Earth’s most novel animals, may also be the most threatened by the thawing of the Arctic.
The thick ice that covers the Arctic Ocean is shrinking more in the summers and rebounding less in the winters. As a result, more ships are setting course across the top of the world.
That means some of the distinctive marine mammals that live in the Arctic, like walruses, polar bears and Beluga whales, are more likely to have close encounters with humans. And no species may be most at risk than the narwhal—a small whale with a big tusk, resembling a kind of aquatic unicorn.
“As passages open up, ships move through. They move though key areas that whales use every year, annually and predictably,” said Kristin Laidre, a marine biologist at the University of Washington. That could push them out of key areas, raise the odds of collisions and oil spills—and throw off their senses with noise.
“Narwhals use sound for pretty much every life function, to find prey and communicate and navigate,” said Laidre, who has studied the unique animals for about 18 years. “Any additional shipping introduces disturbances in the Arctic soundscape.”
Narwhals can grow up to 18 feet (5.5 meters) long. The males’ distinctive tusk is actually a long, spiraling tooth packed with sensitive nerve endings. They feed on fish like halibut and cod in the frigid waters off Greenland and Canada. And unlike their cousins the belugas, which can be found all around the Arctic Circle, they tend to stick close to that patch of sea. That limited range and a pickier diet make them more vulnerable than other species, Laidre said.
Laidre and her colleague Donna Hauser are the authors of a new study that looks at the risks of that growing ship traffic in late summer, when the Arctic icepack is typically at its smallest and the waters are most open to shipping. Vessels range across nearly two-thirds of the Arctic during that period, especially between Norway and Greenland and off Alaska. When Hauser and Laidre compared the ranges of known mammal populations to records of that ship traffic, narwhals topped the list of vulnerable species.
“We are currently at a point where global shipping is poised to expand into this remote, ecologically and socially sensitive and data-limited region,” Hauser said.
Some ships have begun making those runs already. The first large cargo ship went through the Northwest Passage between Greenland and Alaska in 2013, while a specially-equipped liquid natural gas tanker sailed the Northern Sea Route along the coasts of Russia and Scandinavia last summer.
Those effects are expected to speed up as heat-trapping carbon dioxide released by the burning of fossil fuels like coal, oil and natural gas builds up in Earth’s atmosphere. The high latitudes of the Northern Hemisphere are warming twice as fast as the rest of the globe, and U.S. government scientists have said a “new normal” of warmer, more open seas and less ice and snow is here. Navy Secretary Richard Spencer told a Senate committee in April that service’s plans for the region needed an update because “the damn thing melted.”
With a population estimated at more than 170,000, narwhals aren't considered a threatened species right now. But because they’re so skittish, there’s a lot researchers don’t know about them, Laidre said.
“They tend to be far offshore. They don’t come close to land. It’s hard to get close to them,” she said. “You might try to approach them in a boat and they’ll be gone – they’ll just disappear.” And a 2017 study by U.S. and Danish scientists showed narwhals can suffer from “extreme stress” on their hearts and blood vessels in response to threats.
Walruses, which already are considered a threatened species, ranked second in Hauser and Laidre’s study. They were followed by bowhead whales and belugas, bearded and ringed seals, and polar bears—which had the lowest risk largely because they spend so much of their time on land during that period.
The warming trend is not only bringing people but other species into the Arctic. Non-Arctic fish and other mammals like killer whales -- which can prey on narwhals -- are migrating northward as the oceans warm up. And increasing human traffic also brings the risks that invasive species could stow away on the hulls or in the ballast water of passing ships, said Simon Walmsley, senior adviser for sustainable development for the WWF's Arctic program.
“In the Arctic previously that wasn’t so bad because of the thermal barrier—basically, it was too cold,” Walmsley said. But as the temperature difference between the Arctic and the northern Atlantic or Pacific shrinks, invasive species “could be a huge problem.”
“If you have a species that comes in and takes over the niche of another species, you can lose prey or change habitat,” he said.
The thaw has also brought increased interest in the oil and gas deposits believed to lie beneath the sea floor now that the price of oil is rising again, Walmsley said. A major oil spill in the Arctic “would be a nightmare,” he said.
Those risks have conservation organizations and governments scrambling to protect the delicate and rarely touched environment. The U.N. agency that oversees shipping has adopted a “Polar Code” for vessels operating in the far North. Walmlsey said it doesn’t focus enough on environmental protection, but does at least offer guidance for avoiding marine mammals. Steps that have been taken at lower latitudes, such as reducing speeds around known whale routes, would reduce both the risk of a collision and the underwater acoustic effects, but regulations have been limited by a lack of data in the Arctic.
Without further steps, “We’ll lose those species,” he said. “They’re massively under threat many different ways. Climate change, food, oil spills, chemical contamination, plastics—you name it.”