Humpbacks Might Someday Steer Clear of Hawaiʻi Because of Climate Change

A new paper by a research team that included three University of Hawaiʻi at Mānoa graduate students found that humpback whales might one day avoid Hawaiian waters because of climate change and increasing greenhouse gases.

The paper was recently published in Frontiers in Marine Science. The UH-Mānoa students who were part of the research team were 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.

According to von Hammerstein, Setter, van Aswegen and co-researchers from the Pacific Whale Foundation, climate change is warming the oceans at unprecedented rates. At the current pace, it is likely some humpback breeding grounds — tropical coastal waters, including those around the Hawaiian Islands, where sea surface temperatures range from 70-82 degrees — will become even warmer throughout the next century.

Research suggests two possible climate change scenarios:

• By 2100, in a worst case scenario with continuing high development and unabated carbon emissions, 67% of humpback whale breeding grounds will surpass the critical sea surface temperature of 82 degrees.
• In a “middle-of-the-road” scenario, with global and international institutions working toward emission mitigation goals, that number would fall to 35% of breeding grounds.

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

“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 in the release

While it is not known whether humpback whales will continue to migrate to breeding grounds with temps of more than 82 degrees, the researchers hope their findings can be an incentive for policymakers to work toward reducing emissions 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 in the press release. “Improving our understanding of how ecosystems are going to change is critical for the effective and timely implementation of mitigative measures.”