A new study released on Dec. 13 attributes the catastrophic loss of roughly four million of Alaska’s common murre seabirds to the 2014-2016 Pacific Marine heatwave.
The persistent loss of Alaska’s dominant seabird during the heatwave represents the largest documented vertebrate die-off linked to warming oceans, according to the study released by EurekAlert – a publication of the American Association for the Advancement of Science.
Study authors, led by Heather M. Renner with the U.S. Department of the Interior, said that although research on the impacts of global warming on marine birds clearly suggests major shifts in species’ ranges and abundance, documented changes have been gradual, from years to decades.
“To our knowledge, this study is the first to show that climate impacts can be swift (1 year) and intense (eliminating half of the population),” they wrote.
Marine heatwaves – which are intense, prolonged and expansive warming events – are becoming increasingly common because of climate change and are reshaping marine ecosystems globally, the study said.
These heatwaves have led to mass mortality of key habitat-forming species like kelps and corals, triggering cascading trophic effects that alter ecosystem productivity, displace lower-trophic-level species, and amplify food shortages for top predators.
While many upper-trophic-level species suffer from reduced reproduction, increased mortality and even massive die-offs because of marine heatwaves – broader population impacts are poorly understood, the study said. Renner and her colleagues at the University of Washington evaluated the impact of the 2016-2024 heat wave in the northeast Pacific on Alaska’s common murre seabirds. They analyzed colony counts before 2008-2014 and after 2016-2022 and documented a 52%-78% population decline across 13 murre colonies, equating to the loss of four million birds in less than two years.
The authors concluded that this represented the largest documented wildlife mortality event in the modern era. Their findings also revealed no evidence of population recovery since, which suggests potential long-term ecosystem shifts and an overall diminished capacity to support historical seabird populations.
“We suggest that the pronounced decline of an abundant and widespread upper trophic predator to less than half of its former population size in Alaska may signal a new threshold of response to global warming,” they said.
