Arctic shipping noise is silencing narwhals and shifting their movements, study finds

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On the floe edge near Pond Inlet, in the northern part of Baffin Island, Nunavut, narwhal pods are migrating to open waters.

As landfast sea ice retreats and shifts to create passageways through open water, the ice-loving toothed whales journey into Eclipse Sound – the eastern Arctic entrance to the Northwest Passage – before venturing deeper into coastal inlets to forage for foods.

But what also drives narwhals to these sheltered bays is shipping season, which begins in mid- to late July and extends into late fall. Inuit, who rely on the tusked Arctic whales as a traditional food source, have long understood that in the presence of shipping noise narwhal behaviour changes in terms of how they communicate and where they go.

Now, a study published last week in the peer-reviewed Nature journal, Scientific Reports, shows narwhals are more sensitive to such noise than previously known – highlighting the need for long-term monitoring of wildlife, environmental conditions and human activities to better predict the movements and behaviours of Arctic marine species.

“We’re starting to understand that the impacts of having constant ship traffic is having long-term effects and displacing narwhals to neighbouring communities,” says Alexander James Ootoowak, an Inuk hunter from Pond Inlet who is part of the research team that undertook the study.

The largest vessels passing through Eclipse Sound are the bulk carriers and supply ships servicing the Mary River Mine, an iron ore mine on Baffin Island operated by Baffinland Iron Mines Corporation. Other vessels that traverse these Arctic waterways include cruise ships and pleasure-crafts, cargo and supply ships transporting food and fuel, the Canadian Coast Guard, and fishing and hunting boats.

The study builds on the team’s previous research in this region to detect narwhal sounds, understand the natural underwater sounds encountered by narwhals, and assess the additional noise introduced to their environment by maritime transportation.

Unlike the earlier studies, this one offers specific insights into how narwhals react to ship noise. To understand the species’ responses to vessels in Eclipse Sound, the research team examined underwater acoustic recordings and ship tracking data collected over a five-year period, between 2016 and 2021.

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“Narwhals use echolocation clicks primarily for navigation and foraging, and these clicks can be consistently detected in our acoustic recordings when narwhals are present nearby,” says Jack Ewing, the principal author of the study and researcher in the Whale Acoustics Lab at the Scripps Institution of Oceanography at the University of California, San Diego.

The team’s main finding was an inverse relationship between ship proximity and narwhal acoustic presence.

“We found that within 20-kilometre distance between ships and the recorder, as ships get closer, narwhals appear to either go quiet or move away from the area,” Mr. Ewing said.

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While previous studies have established a link between increased underwater noise from rising shipping traffic and marine mammal vulnerability, none adequately captured how sensitive narwhals are to shipping noise pollution, said Joshua Jones, an oceanographer from the Scripps Institution of Oceanography at UCSD who specializes in the use of passive acoustic monitoring.

“Inuit were saying repeatedly during the environmental impact assessment process that narwhals are sensitive to disturbance from noise and that they have excellent hearing from very low to very high frequencies. That was different from the predictions based on studies of other whale species in other regions,” he said.

The study is the result of extensive local partnership, including with the Mittimatalik Hunters and Trappers Organization, which Mr. Ootoowak said is considered “the eyes and ears of hunters and community members in Pond Inlet.”

Twenty years ago, the Committee on the Status of Endangered Wildlife in Canada assessed the narwhal as “special concern,” meaning it is sensitive to human activities or natural events but not threatened or endangered. With a Canadian population estimated at roughly 161,000, mostly mature adults, the narwhal is “not at risk,” the committee reported last year.

“Catches are well within sustainable limits, but a bigger issue is the impact of climate change over time, and then related to that, industrial development, ship traffic over time. Will it increase? How much will it increase?” said Michael Hammill, co-chair of the committee’s marine mammals panel, referring to a decline in sea ice due to climate change that affects both narwhals’ seasonal movements and the length of shipping season.

With increased shipping over the past 20 years, Kristin Westdal, a marine biologist and science director at the non-profit Oceans North said she’s encouraged to see this “unseen threat” garner greater global attention.

Last month, Canada and Panama launched a High Ambition Coalition for a Quiet Ocean, which aims to curb noise pollution caused by the global shipping industry to protect marine life. To date, 37 countries, which represent more than 50 per cent of the globally flagged fleet, have signed the declaration.

“We have this opportunity now, where we’re seeing this increase in vessels, and we’re seeing this response in marine mammals, but we’re not at a doom and gloom state yet. It’s this opportunity to get ahead,” she said.

In an attempt to reduce the threat of underwater radiated noise, Fisheries and Oceans Canada is planning to release its Ocean Noise Strategy later this year, while Transport Canada operates a number of seasonal measures, such as vessel slowdowns and rerouting of vessel traffic in sensitive areas for endangered whales. However, no such federal regulations are in place in Pond Inlet, given narwhals are designated as “not at risk.”

As a result, Baffinland has implemented its own measures, in consultation with local communities, to reduce vessel noise and mitigate potential effects on sensitive species, says Peter Akman, the company’s head of stakeholder relations and communications.

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“Our approach includes reducing vessel speeds to minimize noise and disturbance, implementing a designated marine shipping lane, avoiding ecologically sensitive areas, and scheduling vessel transits to avoid breaking ice at the beginning of the shipping season. We also require vessels to maintain minimum distances from marine mammals and to follow strict protocols,” Mr. Akman said.

Among those protocols are speeds no faster than nine knots, the use of convoys whereby vessels travel as a group, and relying on trained Inuit marine monitors to track vessels as well as observe and report on marine activity in real time.

Canada is also working with the International Maritime Organization, the UN specialized agency that regulates international shipping, to promote a longer-term solution that stands to be more effective than reducing vessel speeds: designing quieter ships.

“A slowdown is only good where they slow down. And in some places, it’s actually not safe to slow down. Or some ships are louder when they slow down,” Michelle Sanders, the alternate permanent representative of Canada to the IMO, said last month at the United Nations Oceans Conference in Nice.

This story is produced in partnership with the Pulitzer Center’s Ocean Reporting Network.