Melting sea ice means more for whales and polar bears than simply habitat loss. A new study suggests that a dramatic jump in Arctic shipping traffic, thanks to longer open-water seasons, could put a host of Arctic-dwelling marine mammals at risk.
As summer sea ice coverage retreats, shipping routes such as the Northwest Passage have become ice-free during warmer months, boosting the number of seagoing vessels by three-fold in some regions. With some projections suggesting the Arctic’s summer sea ice could vanish by 2040, such traffic is only expected to balloon further.
The more ships that pass through, the more likely mammals are to be struck, stressed by underwater noise, or have their daily activities interrupted.
To determine which animals are most vulnerable, researchers looked at 80 populations of seven species, including belugas, narwhals, bearded seals, and polar bears. For each population, they computed what they called a “vulnerability score,” based on two factors: how major shipping routes will likely overlap with each group’s habitat and how sensitive each population is to vessel traffic. Sensitivity scores were based on data about animal-ship collisions, noise disruptions, and how current ship traffic interferes with daily activities like mating, migrating, and foraging for food.
On thin ice
As melting sea ice boosts Arctic ship traffic, these marine mammals may be most at risk from collisions, disrupted migrations, and noise-induced stress. Vulnerability scores are averaged from multiple populations.
Narwhal populations had the highest average vulnerability scores, followed by walruses, bowhead whales, and belugas, researchers report this week in the Proceedings of the National Academy of Sciences. Polar bears and ringed seals had the lowest scores, likely because these species spend most of the open-water season on land, where they aren’t generally disrupted by shipping traffic.
The researchers, who acknowledge some uncertainty caused by incomplete data, say their study is only the beginning; more data are needed to understand how individual species and the ecosystem as a whole will be affected by increased traffic.
For now, the researchers hope their results will lead to less-disruptive shipping routes—or at least quieter ships to help Arctic mammals keep their cool.