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Slowdowns could reduce noise impacts of increased Arctic shipping

Animal Communication, Ocean, shipping Add comments

Several recent studies highlight the heightened risks of increased Arctic shipping, along with some opportunities to minimize the effects of shipping noise on specific Arctic species and populations.

With the retreat of sea ice, both the Northwest Passage (along Canada’s northern coast) and the Northern Sea Route (along Russia’s northern coast) are seeing increases in commercial and fishing vessel traffic. While the first cruise ship crossed the Northwest Passage in 2016, Russia’s Northern Sea Route is the current center of activity, with both container ships and LNG (natural gas) tankers making pioneering transits without icebreakers over the past two summers.  Total ship numbers are still modest, as it’s not yet cheaper than the longer route through the Suez canal, but these test runs are explicitly intended to chart the course for rapid increases in the coming years; Russia aims to ship 80 million tons of cargo by 2024, up from 10 million tons in 2017 and 2018, and China is moving rapidly to implement a “Polar Silk Road” initiative to encourage companies to build the infrastructure necessary to ramp up this shortcut to European markets.

Two recent studies address key questions about the biological impact of increased shipping on Arctic ecosystems.  The first, from researchers at the University of Washington and the University of Alaska at Fairbanks, examined the ranges of 80 localized subpopulations of seven key Arctic species, and found that just over half (42) of these would hear increased shipping noise.  Of these, some species are more vulnerable than others:

“Narwhals have all the traits that make them vulnerable to vessel disturbances — they stick to really specific areas, they’re pretty inflexible in where they spend the summer, they live in only about a quarter of the Arctic, and they’re smack dab in the middle of shipping routes,” said co-author Kristin Laidre, a polar scientist at UW Applied Physics Laboratory’s Polar Science Center. “They also rely on sound, and are notoriously skittish and sensitive to any kind of disturbance.”

In addition to narwhals, beluga and bowhead whales and some subpopulations of walrus are likely to be vulnerable to increased noise; ringed and bearded seals, as well as polar bears, will be less vulnerable, thanks to widespread populations and spending much of the summer on land rather than in the water.  In addition, the researchers stressed that the Bering Strait is a key chokepoint for both Arctic sea routes, as well as being a crucial migratory corridor.

“I think we can learn a lot from areas that have already been thinking about these kinds of conflicts between ships and marine mammal populations — for example the North Atlantic right whale, or fin and blue whales around California,” Laidre said. “We could aim to develop some mitigation strategies in the Arctic that help ships avoid key habitats, adjust their timing taking into account the migration of animals, make efforts to minimize sound disturbance, or in general help ships detect and deviate from animals.”

A second study took a different tack, looking at whether speed reductions (as implemented in some areas around busy ports) would reduce the noise impacts.  They used an increasingly common metric, “listening space,” the area or volume of water within which an animal can hear its brethren, its prey, or other biologically important sounds. The researchers modeled ship noise in several key chokepoints on the Northwest Passage, calculating the distance over which vessels sounds would impact the listening space for several species, and at how much the effect could be moderated if the ships were slowed in key areas.  And indeed, the effects were significant:

Under quiet conditions, beluga whales experienced a 50 percent listening space loss when they were 7 to 14 kilometers (4.3 to 8.7 miles) away from a ship traveling at 25 knots. When ships slowed to 15 knots, whales could get as close as 2 to 4 kilometers before they experienced the same loss of listening space.

In other words, when a ship was going faster, the area over which it cut a beluga’s listening space in half might be more than three times larger. This difference is important because there are many places where whales cannot distance themselves from ships in the Arctic (in the narrow Prince of Wales Strait, animals can maintain a maximum distance of just 7 to 10 kilometers).

As always, the results are not all as simple as that; the researchers found that for some species, the effects are less in certain weather conditions or for different kinds of ships (container vs. cruise), and that in some situations, the effects can actually cover a larger area when ambient noise is high (as it increasingly is with loss of ice cover). And, as always with vessel-slowing programs, planners must consider the tradeoffs between moderating the noise level and increasing the time during which ships are audible during slower passages.

With the inevitable increase in Arctic shipping, it will be crucial for both governmental and commercial players take steps to minimize the acoustic impacts in these remote waters, among the last areas in the seas where human noise intrusions have been relatively modest.

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