Scientists solve mystery behind largest species die-off in recorded history

A marine heatwave known as "the blob" caused the largest single-species die-off in modern history, decimating half of Alaska’s population of the common murre, a seabird that resembles a flying penguin. A new study published in the "Science" journal has reached the devastating conclusion that shifts in food webs and ecosystems led to the species' mass starvation, highlighting the devastating consequences of oceanic warming, not only for individual species but also for the broader ecological and cultural systems dependent on them.

The blob, an expansive mass of unusually warm water in the Pacific Ocean off North America, raised ocean temperatures by up to seven degrees Fahrenheit between 2014 and 2016, destabilizing marine ecosystems and diminishing food supplies for seabirds. The common murres, as described in the Science Daily publication which reported on the findings of the study, rely on fish, squid, octopus, and crustaceans for sustenance and were left starving due to the disruption of the food web caused by the heatwave. 

Before the heatwave, approximately 8 million common murres inhabited Alaska, representing about a quarter of the global population. Researchers, led by the US Fish and Wildlife Service and co-authored by Julia Parrish, analyzed data from 13 murre colonies surveyed between 2008 and 2022. They found a 50% reduction in colony size in the Gulf of Alaska following the blob with the species most alarmingly showing no signs of recovery. The catastrophic decline underscores the severe impacts of ocean warming on animal populations, as detailed in a study published in Science. 

The study revealed that the die-off was not due to direct thermal stress on the birds but rather to food scarcity caused by shifts in the marine food web. This lack of sustenance proved fatal for the murres, marking a significant and lasting impact of the heatwave on this top marine predator. While murre populations have experienced and rebounded from smaller die-offs in the past, researchers warn that this unprecedented decline might be too severe for Alaska’s murres to recover from.

The loss of common murres also affects Alaskan Native communities, where the birds have been a vital source of food and cultural significance. The population decline threatens traditional harvesting practices and cultural connections, compounding the ecological disaster with human and cultural costs.

The blob, identified as the most intense marine heatwave in recorded history, destabilized weather patterns and coastal ecosystems from California to Alaska. Scientists fear that as climate change drives more frequent and intense marine heatwaves, such events could become increasingly common, posing ongoing threats to marine species like the common murre. 

By Nazrin Sadigova