Bird Deaths Caused by 'Blob' Were 'Way Worse' Than Thought

After a marine heatwave called "the Blob" killed off large numbers of a seabird called the common murre along the West Coast between 2014 and 2016, scientists estimated that up to 1 million birds had died. But it was "way worse than we thought," US Fish and Wildlife Service wildlife biologist Heather Renner tells the Washington Post. Renner is the lead author of a study published in the journal Science that estimates at least 4 million common murres died in the "largest documented wildlife mortality event in the modern era." Renner, supervisory wildlife biologist at the Alaska Maritime National Wildlife Refuge, and her colleagues believe the two-year heat wave killed off more than half Alaska's population of the birds.

"To put this in perspective," Renner says in a Fish and Wildlife Service report, "the common murre die-off was approximately 15 times larger than the number of seabirds killed during the Exxon Valdez oil spill, an environmental disaster of epic proportions." The National Audobon Society describes the common murre as a large auk that "sits upright on sea cliffs, looking like a northern version of a penguin." The researchers believe they starved to death as the "blob" of unusually warm water, which stretched for 1,000 miles, disrupted marine food chains. They described the loss as "catastrophic and persistent," noting that common murre numbers have not recovered, suggesting there has been a permanent change in the ecosystem.

The researchers say they were able to get a more accurate picture of the loss with before and after counts at breeding colonies in the Gulf of Alaska and the Eastern Bering Sea. "We saw exactly the same really clear signal at every single colony," Renner says. "It wasn't some of them, it was all of them." Mark Mallory, a seabird biologist at Acadia University in Nova Scotia, tells the New York Times that the die-off reminds him of how overfishing caused the collapse of the Newfoundland cod fishery more than 30 years ago. "Here we are decades after that catastrophic event, and that marine ecosystem has not recovered," he says. "It's entirely conceivable to me that we are witnessing the early stages of a similar effect, caused by a different catastrophe, in these Alaskan waters." (More bird die-off stories.)