Major Die-Off of Common Murre Population Marks Largest Recorded Decline in Marine Heat Wave
A marine heat wave in 2014-2016 led to the loss of approximately half of Alaska’s common murre population, according to a recent study published in the journal Science. This die-off marks the largest recorded decline of a single species in modern history.
The Northeast Pacific heat wave, also known as "the Blob," lasted from late 2014 to 2016 and resulted in temperatures rising by 2.5-3°C above normal levels. Common murres, known for their distinctive black-and-white feathers, are key predators in regulating energy flow in the marine food web. They typically recover quickly from environmental factors, but this heat wave had a catastrophic impact on their populations.
Researchers found that by the end of the heat wave, more than 62,000 common murre carcasses had been counted, accounting for a fraction of the actual loss since many dead birds never appear on land. Monitors also reported no signs of colonies returning to their previous sizes.
The researchers attributed the catastrophic loss to a decline in food supply, specifically Pacific cod, which dropped by 80% between 2013 and 2017. With their key food source collapsed, an estimated 4 million common murres died in Alaska between 2014 and 2016. This equates to half the population, akin to losing 8 million people in New York City in a single winter.
The study revealed that while 25% of the world’s common murre population lived in Alaska before the heat wave, the seven-year period after saw a decline in 13 monitored colonies between 52% to 78%.
Dr. Brie Drummond, a wildlife biologist at the Alaska Maritime National Wildlife Refuge, noted that "there are only two ways" for the population to recover: "Either food comes back to normal levels or they adjust their breeding and nesting habits."
Colleagues in the field agreed, highlighting shifts in marine ecosystems and changes in food supply as driving forces. However, ongoing research is needed to understand why the population isn’t recovering as expected. With rising temperatures driving ecological shifts and potentially affecting populations of various marine species, researchers emphasize the need for long-term monitoring and ecological assessments.
