Nearly three-quarters of dolphins, whales and seals under U.S. jurisdiction are highly vulnerable to climate change, a new study has found.
Warming oceans, rising seas: Climate change could have stark effects on the distribution, behavior and movements of marine mammals, according to the study, published on Wednesday in PLoS One.
Rising ocean temperatures and sea levels could yield lower levels of dissolved oxygen, declining sea ice coverage, acidification and salinity shifts, per the study.
Disrupted distribution: “Marine mammal species with restricted geographical distributions and habitat tolerances will have limited opportunities to adapt to the changing conditions of their environment,” the authors warned.
Leading the study, which included researchers from across the country, was Matthew Lettrich of the National Oceanic and Atmospheric Administration’s Fisheries branch.
From the North Atlantic to the Caribbean: To understand the magnitude of these climate-related threats, Lettrich and his colleagues conducted what is known as a “climate vulnerability assessment” for marine mammals.
- Such assessments provide a framework for evaluating climate effects for a broad range of species.
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The scientists implemented this trait-based appraisal for 108 U.S. marine mammal stocks in the western North Atlantic, the Gulf of Mexico and the Caribbean Sea.
How did they quantify vulnerability? The researchers assigned scores to each marine mammal stock in two district categories:
- 1. Degree of exposure to climate change — scored by accounting for 16 factors likely to impact marine mammals, their prey or their habitat.
- 2. Sensitivity and capacity to adapt to the resultant environmental shifts.
What did they find? The scientists determined that 72 percent of U.S. cetacean (whales, dolphins, porpoises) and pinniped (seals, sea lions, walruses) stocks are highly or very highly vulnerable to climate change.
About 44 percent of marine mammal stocks had a “very high” climate vulnerability score, according to the study.
Which mammals were most at risk? Baleen whales, toothed whales, medium-sized whales and dolphins were among mammals most vulnerable to the effects of climate change, the authors observed.
And the biggest factors driving that change? Ocean temperature, acidity and dissolved oxygen were the biggest drivers of impacts from climate change, according to the study.
- These effects altered the availability of prey and habitat for marine mammals.
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Changes in acidity and temperature can also alter sound absorption and transmission, disrupting echolocation among certain species.
What can be done? The authors voiced their support for conducting a repeat climate vulnerability assessment, when more enhanced input data is available.
Some such tools, they explained, could include higher-resolution climate projects and better species-specific biological data.
Refining responses to climate change: “Using a systematic approach allowed us to look across all of these stocks and better understand what drives their vulnerability to climate change,” Lettrich said in a statement.
“We can now go out and look at some of these individual responses to climate change, and explore approaches to reduce the impacts of climate change on these vulnerable populations,” he added.
