Alaska’s Scorching Heat Claims Lives of 4 Million Seabirds: A Grim Record

Subscribe to CNN’s Wonder Theory science newsletter. Discover the universe with updates on intriguing findings, scientific progress, and more.

CNN
 — 

A marine heat wave has resulted in the death of approximately 50% of Alaska’s common murre population, representing the most extensive recorded mortality of a single species in contemporary history, research indicates. This devastating decline suggests widespread alterations in marine habitats influenced by rising ocean temperatures, which are rapidly and significantly transforming ecosystems and hindering the capacity of these animals to flourish, as outlined in a recent study.

The Northeast Pacific heat wave, termed “the Blob,” affected the ocean ecosystem from California to the Gulf of Alaska between late 2014 and 2016.

This event is recognized as the largest and longest documented marine heat wave, with temperatures escalating by 2.5 to 3 degrees Celsius (4.5 to 5.4 degrees Fahrenheit) above average levels, stated Brie Drummond, coauthor of the study published on December 12 in the journal Science.

Common murres, or Uria aalge, are distinguished by their unique black-and-white plumage, resembling the tuxedo look of penguins. These predators play an essential role in maintaining energy flow within the marine food web of the Northern Hemisphere.

Although murres have faced smaller population declines in earlier years due to environmental and anthropogenic factors, they usually rebound quickly when conditions become favorable. However, the scale and rapidity of the die-off during this heat wave were particularly concerning to Drummond and her research team.

The researchers assessed the extent of this devastating population decline by observing drastic population reductions at 13 colonies throughout the Gulf of Alaska and Bering Sea that have been observed over a long period. By the conclusion of the 2016 heat wave, Drummond and her team identified over 62,000 common murre carcasses, which represented only a small portion of those lost, as the majority of deceased seabirds are rarely found on land.

Subsequently, biologists tracked the mortality and reproduction rates of common murres and observed no indications of the colonies returning to their former numbers.

“The only reason we possessed this information and could identify this (event) was because we had these long-term data sets and enduring monitoring,” remarked Drummond, a wildlife biologist at the Alaska Maritime National Wildlife Refuge. “(Monitoring) is the sole method by which we can continue to observe what transpires in the future.”

Prior to the 2014–2016 Northeast Pacific marine heat wave, a common murre census plot at the Semidi Islands, Alaska, contained 1,890 birds (left). By 2021, the plot registered 1,011 birds (right).

As temperatures in Alaska increased, the murres’ food resources diminished, with one of their main targets, Pacific cod, decreasing by approximately 80% between 2013 and 2017, the research indicated. The collapse of this vital food resource resulted in around 4 million common murres perishing in Alaska during the timeframe from 2014 to 2016, according to the scientists’ estimates.

“There are roughly 8 million residents in New York City, so it would be akin to losing half of the population … in just one winter,” Drummond remarked.

Prior to the onset of the 2014 heat wave, the murre population in Alaska represented 25% of the global population of this seabird species.

Nevertheless, when assessing the seven-year time frame preceding the heat wave (2008 to 2014) and the seven-year span that followed (2016 to 2022), the study uncovered that the murre population across 13 colonies dispersed between the Gulf of Alaska and Bering Sea contracted between 52% and 78%.

Drummond and her associates maintained observation of the murres from 2016 to 2022 following the conclusion of the heat wave but did not observe any indications of recovery.

While additional studies are essential to completely comprehend why murres are failing to rebound, Drummond’s group posits that the alterations stem from shifts in the marine ecosystem, particularly those related to food availability.

Reproductive challenges and difficulties in relocation might also be playing a role in the species’ inability to recover, according to Dr. Falk Huettmann, a wildlife ecology associate professor at the University of Alaska, Fairbanks, who did not participate in the study.

Unlike certain other species, seabirds like murres require a longer period to reproduce, leading to a more gradual repopulation process, remarked Huettmann.

Furthermore, Huettmann pointed out that murres are tied to the colonies they inhabit, making it more challenging to adapt to new environments when they are compelled to relocate.

As temperatures persist in rising in regions such as Alaska, tropical or subtropical waters are shifting into new areas, Huettmann noted, thereby creating conditions conducive to an entirely different ecosystem.

Amidst these environmental transformations, animals will either adapt or struggle to endure in the new climate.

Murres are not the sole species in Alaskan waters experiencing substantial changes. Huettmann mentioned that the tufted puffin, a delicate marine bird, has been observed migrating northward due to adverse conditions in southern regions of the North Pacific, including California, Japan, and Russia, yet it is struggling to acclimatize to its new surroundings. Other species like king salmon, whales, and crabs are also facing challenges in finding their new niches, he stated.

While heat waves have impacted numerous species, other populations remain largely unaffected, remarked Drummond.

Half of the data obtained from organisms such as phytoplankton and even homeothermic top predators exhibited “neutral” responses to the heat wave. Additionally, twenty percent of these apex predators reacted positively to the unusual heat exposure, according to the research.

Homeothermic creatures, including birds and mammals, maintain stable internal body temperatures regardless of the surrounding temperature.

“This provides us insight into which species may more readily adapt to these types of warming water events in the future and which may not,” Drummond commented.

Though increasing temperatures are the main element affecting animals like murres, other factors may also be contributing to changes in marine life.

“From an ecological viewpoint … microplastics, ocean acidification, rising sea levels, and chronic oil spills … represent other significant mortality factors in action,” Huettmann stated.

Nonetheless, research tracking the prolonged effects of climatic phenomena on marine life is scarce, leaving scientists uncertain about how these creatures will continue to be affected moving forward.