Physical Address
23,24,25 & 26, 2nd Floor, Software Technology Park India, Opp: Garware Stadium,MIDC, Chikalthana, Aurangabad, Maharashtra – 431001 India
A catastrophic marine heatwave, fueled by climate change, has killed nearly four million common murres (Uria aalge) in Alaska, marking the largest single-species wildlife die-off in recorded history.
This unprecedented event spanning 2014 to 2016, detailed in the journal Science, highlights the serious impacts of rising ocean temperatures on marine ecosystems, serving as a strong warning about the ever-increasing threats posed by global warming.
The Heatwave and Its Devastation
Known as “The Blob,” the Northeast Pacific heatwave engulfed the region from California to the Gulf of Alaska, elevating sea surface temperatures by 2.5 to 3 degrees Celsius (4.5 to 5.4 degrees Fahrenheit) above average. Lasting three years, the anomaly drastically altered ecosystems and disrupted food chains vital to marine species. Common murres, highly resilient diving seabirds, bore the brunt of this unusual weather.
Alaska, home to approximately eight million murres—a quarter of the global population—saw nearly half of its seabirds perish. Declines ranged from 52% to 78% across 13 monitored colonies.
before and after the 2014–2016 northeast Pacific marine heatwave.
Common murres in 2014 (before the heatwave; left) and in 2021 (after the heatwave; right) on two census plots (A and B) in the Semidi Islands, Alaska.
Causes of the Mass Die-Off
Starvation emerged as the chief cause of the Murres’ deaths. The heatwave severely impacted the availability and quality of fish that the murres forage, such as small schooling species and juvenile predatory fish. Populations of the Pacific cod, a key food source, declined by about 80% in the Gulf of Alaska during this period, leading to mass starvation and the deaths of millions of murres.
The study also noted that several colonies exhibited signs of decline even before the heatwave, indicating pre-existing stressors heightened the seabirds’ susceptibility. Seven years later, many colonies remain unrecovered, with reproductive rates and population sizes still far below pre-heatwave levels.
Bubbles are scaled to the number of individual murres that were recorded at each colony before the 2014–2016 heatwave. Population changes after the heatwave at 13 monitored colonies are shown in colour; colony names are noted in parentheses when loss was calculated from arithmetic means rather than the Bayesian hierarchical model. Grey bubbles represent colonies with no long-term monitoring data available.
Domino Effect on Marine Ecosystems
The heatwave’s impact extended beyond murres. Pacific cod populations collapsed, leading to fisheries closing down, while humpback whale numbers in the North Pacific dropped by 20%. These interconnected disruptions show just how fragile the marine ecosystems are, where disturbances at one level have a ripple effect across species.
A New Threshold in Ecological Responses
Scientists caution that the murres’ mass mortality marks a potential tipping point in ecosystems’ response to global warming. The dramatic decline of a key predator signals the vulnerability of marine systems to climate-induced shifts. “To our knowledge, this is the largest mortality event of any wildlife species reported during the modern era,” the researchers stated.
Challenges Ahead for Murres and Marine Species
Common murres face major challenges in adapting to their altered environment. Unlike some mobile species, murres are tied to specific colonies, complicating relocation and adaptation. Their slow reproductive rates further hinder recovery. Other species, such as tufted puffins and king salmon, also struggle to adjust to the rapidly changing marine environment.
References:
https://www.science.org/stoken/author-tokens/ST-2308/full
https://www.nps.gov/articles/theblob.htm
Image: Science
Banner Image: https://www.usgs.gov/media/images/common-murres-their-colony-cook-inlet-alaska
