Bowhead whales are endemic to the icy waters of the Arctic and prefer living in shallow waters near sea ice, filtering krill and tiny crustaceans called copepods for food. However, the Arctic is warming faster than any other region on Earth, and a recent study estimates that if this continues, then by 2100 the whales could lose up to 75% of the current area where their prime habitat now exists.
Previous studies have looked at their past distributions over small geographic areas and used data from just the last 50 years or so. The new study looks at the whale’s distribution throughout its entire range, examining data going back nearly 12,000 years, from fossil evidence to whaling logbooks to more recent databases and published studies.
The researchers wanted to “build a long-term baseline for this species that stretches back thousands of years so we can understand how resilient they actually will be to future climate change. Use the past as the key to the present,” study lead author Nick Freymueller, a doctoral candidate at the University of Adelaide, Australia, and the University of Copenhagen in Denmark, told Mongabay in a video call.
Their modeling showed that, historically, bowheads whales (Balaena mysticetus) thrived in areas where summer sea ice covered 15-30% of the ocean surface. It also found that such bowhead habitat has been relatively stable for all of the Holocene, the last 11,700 years since the end of the last ice age.
However, even under a moderate-emissions scenario, suitable bowhead habitat is expected to decrease in quality by roughly 50% by 2100. Under a high-emissions scenario, high-quality habitat could decrease by 90%. The area with the warmest habitat today, Russia’s Sea of Okhotsk, will be completely uninhabitable for the whales within the next 35 years, the researchers forecast.
Bowheads might respond to warming by moving north to colder, ice-covered waters; however such areas are frequently too deep and lack sufficient food.
Thought to be the longest-living mammal on Earth, bowheads live for up to 200 years and are listed as endangered under the U.S. Endangered Species Act. They were nearly wiped out by commercial whaling, and fewer than 3,000 individuals remained by the 1920s. Today, they face peril from climate change; and as the Arctic continues to melt, opening up new shipping lanes across the Northwest passage, ship traffic can add further stress to Arctic marine life.
Freymueller said he hopes this study will help identify areas of bowhead whale habitat that will still be suitable for them in the future, “and we can maybe try to design those as nature reserves, or try to usher any sort of ship traffic from going through there, that might at least give some of these species, you know, a better leg up,” he said.
Banner image: A group of bowhead whales off the coast of Alaska. Image courtesy of NOAA.
