Whales may avoid Hawaii as water temperatures warm

Whales may avoid Hawaii waters due to rising temperatures. Photo credit: HIHWNMS NMFS ESA Permit

Humpback whales may one day avoid making the trip to Hawaii’s waters due to climate change and rising greenhouse gasses, according to new findings published in Frontiers in Marine Science.

Three University of Hawaii at Manoa graduate students Hannah von Hammerstein and Renee Setter from the Department of Geography and Environment in the College of Social Sciences, and Martin van Aswegen from the Marine Mammal Research Program in the Institute for Marine Biology said that it is likely that some of the whale’s breeding grounds will heat up past the comfortable temperature range over the next century.

“We expected to see critical warming in some of the breeding grounds, but the number of critically affected areas was a surprise,” said von Hammerstein in a news release. “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.”

In the paper titled “High-Resolution Projections of Global Sea Surface Temperatures Reveal Critical Warming in Humpback Whale Breeding Grounds,” research suggest that anthropogenic climate change is warming the oceans at unprecedented rates.

Humpback whales are known to migrate toward tropical coastal waters, such as Hawaii’s, where they give birth to their calves, according to von Hammerstein, Setter, van Aswegen and co-researchers from the Pacific Whale Foundation.

These areas lay in regions with sea surface temperatures ranging between 7 and 82 degrees Fahrenheit, and the whales typically return to the same sites annually.

Using a statistical “delta down scaling” method to increase the resolution of global sea surface temperatures and track the critical temperature range that border humpback whale breeding grounds throughout the 21st century, research suggested two possible climate change scenarios.

By 2100, in a worst case scenario with continuing high development and unabated carbon emissions, 67 percent of humpback whale breeding grounds will surpass the critical sea surface temperature of 82 degrees.

The second scenario shows that with global and international institutions working toward emission mitigation goals, that number would fall to 35 percent of breeding grounds.

“It’s really crucial that we try to reduce our greenhouse gas emissions and really try to stay on that “middle-of-the-road” greenhouse gas emissions scenario at the very least, just so that we can save as many of those breeding grounds as possible from surpassing that critical temperature threshold,” Setter added.

The researchers noted that, while it is currently not known whether humpback whales will continue to migrate to breeding grounds above 82 degrees, they hope their findings may be an incentive for policymakers to work toward reducing emissions, not only in Hawaii but also on an international level.

“Our findings provide yet another example of what is to come with anthropogenic climate change, with humpback whales representing merely one impacted species,” van Aswegen said. “Improving our understanding of how ecosystems are going to change is critical for the effective and timely implementation of mitigative measures.”

* Dakota Grossman can be reached at dgrossman@mauinews.com.

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