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The first was the feathered bodies Alaskan beaches. They were common murres, sleek black-and-white seabirds that typically spend months at a time away from land. But in 2015 and 2016, officials 62,000 emaciated corpses from California to Alaska.
Since then, scientists have been what happened to the birds, along with other in the northeast Pacific that suddenly died or disappeared. It became clear that the was a record-breaking heat wave, a mass of warm water that would come to be known as the Blob. New findings on its effect on murres, published on Thursday in the journal Science, are a sign of the facing in a warming world.
About half of Alaska’s common murres, some four million birds, died as a result of the marine heat wave, the scientists found. They believe it is the largest die-off of a single species of wild birds or mammals. The state is home to about a quarter of the world’s common murres, scientists say.
Murres were the victims of a domino effect of oceanic changes tied to the warm water, according to a growing body of research. It affected marine life from plankton to humpback whales. Critically for the murres, it led to a collapse in the fish they depend on.
One of the most in the new study is that the birds have not even begun to .
“If the conditions are good, I think there’s hope,” Ms. Renner said. “Our fear is that events like this are predicted to become much more common, and we haven’t seen any signs of at all yet, eight years after the event.”
For decades, the world’s oceans have more than 90 percent of the excess heat produced as humans burn fossil fuels and destroy ecosystems like forests. That heat has coral reefs, kelp forests and other marine ecosystems. Last year and into this year, the ocean’s surface temperature records.
For the murres, earlier estimates from the Blob were lower. In 2020, a team of some of the same scientists estimated that half a million to a million of the birds had died in Alaska. But the new research uses a different and far more reliable method, earlier data to before and after counts at 13 colonies throughout the Gulf of Alaska and the Eastern Bering Sea. The authors then those declines across the entire population.
“We saw exactly the same really clear signal at every single colony,” Ms. Renner said. “It wasn’t some of them, it was all of them.”
Avian flu has had huge on some bird populations around the world, but researchers have not seen much in Alaska, Ms. Renner said, so it does not appear to be playing a major role.
, while various species were by the Pacific marine heat wave, including some fisheries stocks, not all showed declines. That suggests the changes created “pinch points” in the food web rather than, say, all .
Mark Mallory, a seabird biologist and professor at Acadia University in Nova Scotia who was not involved with the study, said the research the importance of long-term data in allowing scientists to understand the changes on Earth.
The finding that murres, a species, are not regaining their numbers, him of what happened when people overfished Atlantic cod stocks off Newfoundland, which had once been thought .
“Here we are decades after that event, and that marine ecosystem has not recovered,” Dr. Mallory said. “It’s entirely to me that we are witnessing the early stages of a similar effect, caused by a different catastrophe, in these Alaskan waters.”