For most of their evolutionary history, narwhals have relied more on sound than sight to survive in the Arctic’s dark icy waters.
The speckled toothed whales—sometimes referred to as “unicorns of the sea” for the long, spiral tusks that protrude from the heads of males—navigate, hunt, and communicate using echolocation. By emitting a series of calls, whistles, and high frequency clicks—as many as a thousand per second—and listening for the echoes that bounce back, they are able to locate prey hundreds to thousands of feet deep and detect narrow cracks in sea ice where they can surface to breathe.
But as global temperatures continue to rise, the acoustic world narwhals depend on is rapidly shifting throughout their range, from northeastern Canada and Greenland to Norway’s Svalbard archipelago and Arctic waters in Russia. It’s getting louder.
The Arctic is warming at least three times faster than the rest of the planet, and as sea ice continues to shrink, vast stretches of ocean, once inaccessible to most humans, are opening up. Over the past decade, cargo vessels, fishing fleets, cruise ships, and oil and gas tankers have started moving through the region with increasing frequency and ease.
Throughout their journeys, they generate disturbing levels of noise that mask the sounds made by narwhals, as well as their hearing.
“Underwater noise is a growing problem, contributing to serious impact on the Arctic ecosystem,” said Sarah Bobbe, senior manager in the Arctic program at Ocean Conservancy, in a statement.
Other whales that are endemic to the Arctic, including belugas and bowheads, are in jeopardy, too.
“We know that all three species are sensitive to underwater noise produced by ships,” said Melanie Lancaster, senior specialist for Arctic species for the global Arctic program at the World Wide Fund for Nature, better known as WWF. “Even small amounts of noise can have large impacts on these species.”
Last month, that growing threat was a central topic at a multi-day meeting convened in London by the International Maritime Organization (IMO)—a United Nations body that regulates global shipping—where they reviewed recent research on the impact of ocean noise pollution on marine life and discussed methods and technologies for reducing it.