Breeding waters getting too hot for humpback whales due to global warming

Gray Whale Festival in Puerto López Mateos BCS January 29-31 (Photo: Baja Insider)

The warm, shallow waters near Hawaii are a renowned breeding ground for humpback whales. An estimated two-thirds of North Pacific humpback whales are born there, and the massive creatures — adult males can be up to 52 feet long and can weigh 45 tons — figure in the mythology of native Hawaiians. For the locals who make their living giving tours to whale-watching visitors, they are also an important part of the state’s economy.

But that may all be upended in the decades to come, due to climate change — and the more greenhouse gases that are emitted this century, the fewer whales there will be in Hawaii, according to a new study.

Humpback whales give birth in waters that range from about 70°F to 82°F, but at their current pace of warming, two-thirds of the waters near Hawaii will surpass 82°F by the end of this century, the study found.

A breaching humpback whale off the Hawaiian coast.
A breaching humpback whale off the Hawaiian coast. (David Fleetham/VW PICS/Universal Images Group via Getty Images)

The paper, published earlier this week in Frontiers in Marine Science, was authored by three graduate students at the University of Hawaii at Manoa and two co-researchers at the Pacific Whale Foundation.

“We expected to see critical warming in some of the breeding grounds, but the number of critically affected areas was a surprise,” said Hannah von Hammerstein, one of the co-authors, in a statement that accompanied the study’s publication.

But the findings were not hopeless. The research also showed that in a “middle of the road” scenario, in which nations cut emissions to a more moderate level, only 35% of current breeding grounds would become too hot by 2100.

“While the results of the study are daunting, they also highlight the differences between the two emission scenarios and what still can be won by implementing emission mitigation measures,” said von Hammerstein, a graduate student in geography and environment.

“Our findings provide yet another example of what is to come with anthropogenic climate change, with humpback whales representing merely one impacted species,” said the paper’s co-author Martin van Aswegen, a graduate student in marine biology.

The Yucatan Times
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