Extreme Heat Provokes Mass Marine Life Die-Off

Heart shaped open mussel shell on the beach. Valentine day background.

by Natasha Lasky, ODP Staff Writer

The one-two punch of heat and drought in the Western United States and Canada isn’t just affecting people— it’s also cooking marine wildlife across the Pacific Northwest. After two weeks, climate-fueled extreme heat has killed an estimated 1 billion marine animals and threatens freshwater life as well, according to a preliminary assessment from Christopher Harley, a marine biologist at the University of British Columbia. 

Terrestrial animals from birds and other wildlife to pets were also severely impacted by these record-breaking temperatures.

Why This Matters: Heat is one of the most deadly forms of extreme weather, for both people and ecosystems — hundreds of people died last week as a heatwave swept over the Pacific Northwest. Meanwhile, the mass deaths of staple foods in marine ecosystems like blue mussels could have a ripple effect on those who rely on them to survive, like sea ducks. 

Many animals had been struggling to survive already because of human interference in their habitats. The chinook salmon, for instance, were already threatened by dams blocking their migration path, but warming waters could put the species at a 90 percent mortality rate

Climate-Fueled Disaster: It would have been impossible for these extreme temperatures to arise without global warming, and it’s predicted that these conditions will only get worse should humankind refuse to curb fossil fuel emissions. 


Like in “Postapocalyptic Movies”

Dr. Harley had estimated the death toll of extreme heat on marine life by looking at the number of blue mussels living on a particular shoreline, and what fraction of the mussels died. What he found was shocking — hundreds of millions of mussels were lost. Factoring in the other sea creatures who inhabit the shore, from barnacles and hermit crabs to worms and sea cucumbers, the death toll could be well over a billion. 

I want to find the positives and there are some, but it’s pretty overwhelming right now,” Dr. Harley, the University of British Columbia marine biologist, told the New York Times. “Because if we become too depressed or too overwhelmed, we won’t keep trying. And we need to keep trying.”

Fatigued Mussels: Mussels and other bivalves are a bedrock species as they provide habitat and food for a multitude of species. While mass die-offs are not unprecedented, scientists have stated that climate change is making these traumatic events more frequent. Mussels are resilient but marine scientists worry that they will be unable to evolve to live through extreme heatwaves.


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