In Alaska, scientists report the largest ever recorded die-off of a single species known to have occurred in modern times, based on concerning new findings.
New research has revealed an unprecedented marine heat wave led to the deaths of close to half of the Alaskan population of common murre, also known as the common guillemot, a short-winged seabird found mostly in low-Arctic regions of the North Atlantic and North Pacific.
The concerning die-off is the result of shifting marine environments near Earth’s poles, driven by increasingly warmer oceans that are causing significant changes to these environments and their resident animal populations.
The new findings have left scientists probing for answers to how such catastrophic die-off events might be prevented amid rising concerns associated with climate change.
Attack of “The Blob”
Between 2014 and 2016, a massive climate event, the Northeast Pacific heat wave, severely impacted marine environments along the California and Alaska coasts. The event, informally known as “the Blob,” represents the longest known marine heat wave in modern history.
“Recent marine heatwaves have had pervasive effects on marine ecosystems, from declines in primary production to die-offs of top predators,” write the authors of a new study on the event, published in Scienceearlier this month.
Although seabird mortalities linked to heatwaves are known to occur, their broader population effects remain poorly understood. In their new study, the research team examined the loss of nearly half of Alaska’s common murre population over a seven-year period, where murre populations declined by 52 to 78% across 13 colonies within two large marine ecosystems.
This equates to an estimated loss of 4 million common murres, marking it as the largest recorded wildlife mortality event scientists have documented in modern history.
“No evidence of recovery has yet been observed, suggesting that these ecosystems may no longer support historic numbers of seabird top predators,” the researchers wrote.
Largest Known Die-Off in Modern History
Although scientists are aware of smaller die-offs of murres that have occurred in the past due to both anthropogenic factors and natural environmental changes, generally these birds are able to recover quickly.
However, the severity of conditions between 2014 and 2016 were such that the magnitude and speed could have far longer-reaching implications.
For their study, the researchers observed extreme population declines at 13 murre colonies along the Gulf of Alaska and the Bering Sea, noting more than 62,000 murre carcasses. Despit that huge number, their observations are believed to only represent a small fraction of the larger total.
Alarmingly, there appeared to be virtually no sign of recovery of these populations that indicated they were returning to their size prior to the heat wave event, according to Brie Drummond, a wildlife biologist at the Alaska Maritime National Wildlife Refuge, who told CNN that monitoring the region and the decimated murre populations will be “the only way we’ll be able to continue to look at what happens in the future.”
Slow recovery rates observed in the region could involve the murre’s slow reproductive cycles, as well as challenges in relocating to new environments. Murres are known to be highly attached to their colonies, making it difficult for them to adapt to new conditions when forced to move.
A Broader Environmental Concern
As temperatures rise in Alaska, tropical and subtropical waters are shifting north, creating new ecosystems that some species struggle to adapt to. Currently, scientists are aware of other species that are encountering challenges, such as tufted puffins which, migrating north from poor conditions in the North Pacific, are now struggling to thrive in their new habitats.
Not all species are negatively affected by marine heatwaves. According to Drummond, around half of studied organisms, including phytoplankton and top predators, showed neutral responses, while 20% responded positively, potentially offering insights into which species can adapt to warming waters.
Along with rising temperatures, there are a range of other environmental concerns that have scientists on alert. These include microplastics, ocean acidification, rising sea levels, and chronic oil spills, all of which have contributed to marine life changes in recent decades.
While scientists are aware of the impact of such environmental stressors, there is a lack of long-term studies on the impact of these climate events, which foments uncertainty about the future of marine ecosystems.
Drummond and her team’s study, “Catastrophic and persistent loss of common murres after a marine heatwave, appeared in Science on December 12, 2024.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.