David Irons was driving past a beach in Whittier, Alaska, on New Year’s Day four years ago when something caught his eye. It was an endless line of white lumps near the water’s edge—piles of something that shouldn’t be there.
They were dead sea birds, and the bodies were everywhere. “I just couldn’t believe it,” said Irons, a recently retired biologist with the U.S. Fish and Wildlife Service. “We started counting them, and we just counted a section and we got to 1,500.”
In all, he and his wife, son and a friend found 8,000 dead birds on a beach about a mile long. A dead zone of common murres—a species known for its resilience.
For almost a year, people had been reporting finding dead common murres up and down the Pacific coastline, from California to Alaska. From the summer of 2015 through the spring of 2016, about 62,000 washed ashore, part of a mass species die-off that scientists are attributing to an extreme marine heat wave.
In a study published Wednesday in the journal PLOS ONE, a group of scientists from various state and federal agencies, universities and bird rescue organizations documented the die-off and concluded from the data that it was caused by a record-breaking ocean heat wave in 2014 through 2016 that triggered systemic changes throughout the ocean ecosystem.
The authors estimate that 1 million common murres died during the period, an event they called “unprecedented and astounding.”