Climate change poses a serious threat to the habitats of the bowhead whale, which may shrink by up to 75 percent by the end of the century, a new projection from the University of Copenhagen shows.
It weighs up to 100 tons, is 18 meters long, and can live for more than 200 years.
This giant of the sea, the bowhead whale, currently thrives in the planet's coldest, northernmost waters.
But the bowhead whale's habitats - and thus the whale itself - are severely threatened by climate change: According to a projection prepared by researchers from the University of Copenhagen, the whale's habitats risk being reduced by up to 75 percent by the year 2100.
"Our study shows that 65 to 75 percent of the bowhead whale's habitat will disappear during this century. This will have enormous consequences for the distribution of the bowhead whale and its ability to survive in the future," says the study's lead author, PhD Nicholas Freymueller from the Globe Institute at the University of Copenhagen and the Environment Institute, University of Adelaide.
The Sea of Okhotsk, located between eastern Siberia and Japan, is home to one of the four existing populations of bowhead whales. Researchers expect this habitat to disappear completely.
"In the Sea of Okhotsk, the whale's suitable summer habitat will likely disappear as early as 2060. This means the species will no longer have suitable habitats in the region," adds Nicholas Freymueller.
The ice is disappearing
The disappearing ice cover is the overwhelming reason why the bowhead whale's habitats are vanishing.
"For millennia, bowhead whales have preferred to forage in sea ice," explains Nicholas Freymueller, who, along with his research colleagues, used computer models, fossils, and whaling ship logs to map the bowhead whale's summer habitat over the past 11,700 years and determine where and how large the habitats have been over time.
The bowhead whale (Balaena mysticetus) is one of the heaviest whales on Earth. It can grow up to 18 meters long and is the only baleen whale that spends its entire life in Arctic waters.
The bowhead whale is one of the few whales that uses song to communicate with others of its kind.
Source: Greenland Institute of Natural Resources
"When we compare our knowledge of the ice cover since the end of the previous ice age 11,700 years ago with fossil records of bowhead whales and whalers' catch logs, we can see that the bowhead whale has preferred to live in areas where the summer sea ice cover is 15-30 percent," explains co-author Professor Eline Lorenzen from the Globe Institute.
The researchers calculated that the whale's habitats have been relatively stable over time despite significant climate changes - until very recently.
"The extent of Arctic sea ice has shrunk significantly in recent years, and this will accelerate in the coming decades, leading to further loss of the bowhead whale's summer habitat," points out Eline Lorenzen.
Historical data can help
Finally, the researchers found that the few areas with potentially suitable habitats expected to remain in 2100 will mostly lie outside the regions where the bowhead whale currently lives. This will also put pressure on the species.
65 to 75 percent of the bowhead whale's habitat will disappear during this century.
"In the future, there will still be areas in the Arctic with the right percentage of ice cover. But they are outside the continental shelf, where the water is much deeper, and therefore there is not as much food," says Eline Lorenzen.
This knowledge can have a direct impact on how efforts to conserve the species are shaped going forward.
"Our models contribute crucial knowledge for the global management of the species by mapping the extent and location of habitats likely to be lost in the coming decades. The study shows how knowledge of the past can improve our predictions about the future when it comes to species' vulnerability to climate change."
Read the study "21st Century Sea Ice Loss Will Upend 11,700 Years of Stable Habitat for Bowhead Whales".
