Heat wave killed marine wildlife en masse

Dead mussels and clams covered the rocks of the Pacific Northwest, their shells gaping as if they had been boiled. The starfish have been cooked to death. Sockeye salmon swam slowly in an overheated Washington River, prompting wildlife officials to truck them to cooler areas.

The combination of extraordinary heat and drought that hit the western United States and Canada over the past two weeks has killed hundreds of millions of marine animals and continues to threaten countless species of seafood. freshwater, according to a preliminary estimate and interviews with scientists.

“It sounds like one of those post-apocalyptic movies,” said Christopher Harley, a marine biologist at the University of British Columbia who studies the effects of climate change on coastal marine ecosystems.

To calculate the death toll, Dr. Harley first looked at the number of blue mussels living on a particular shoreline, what part of the area is good habitat for mussels, and what fraction of the mussels he observed died. . He estimated the losses for the mussels alone at hundreds of millions. If you factor in the other creatures that live in the mussel beds and on the shore – barnacles, hermit crabs and other crustaceans, various worms, tiny sea cucumbers – the death toll easily exceeds one billion, a he declared.

Dr Harley continues to study the damage and plans to publish a series of articles.

Such extreme weather conditions will become more frequent and intense, scientists say, as climate change, caused by the burning of fossil fuels by humans, wreaks havoc on animals and humans. Hundreds of people died last week when the heat wave parked over the Pacific Northwest. A study by an international team of climate researchers found that it would have been virtually impossible for such extremes to occur without global warming.

Just before the heat wave, when Dr Harley took notice of the stunning weather forecast, he thought of low tide at noon, cooking up the mussels, starfish and barnacles on display. When he hit the beach last week on one of the hottest days, the smell of rot hit him immediately. The scientist in him was excited, he admitted, to see the real effect of something he had been studying for so long.

But his mood quickly changed.

“The more I walked and the more I saw, the darker it all got,” Dr. Harley said. “It just went on and on.”

The Dead Sea stars, usually the most eye-catching creatures in tidal pools, hit him particularly hard. But the obvious mass casualties were the blue mussels, an ecologically important species that feeds starfish and sea ducks and creates habitat for other animals.

Scientists have only started to consider domino effects. One concern is whether the sea ducks, which feast on mussels in the winter before migrating to their summer breeding grounds in the Arctic, will have enough food to survive the trip.

“At least that’s something we’re starting to think about,” he said.

Species that live in the intertidal areas are resistant, he noted, and the mussels on the shaded north side of the rocks appear to have survived. But if these extreme heat waves become too frequent, species will not have time to recover.

As the heat wave over the Pacific Northwest eased, distressing temperatures persisted across much of the U.S. West. Now another heat wave appears to be developing, only making the ongoing drought worse.

This means that biologists monitor the temperatures of the rivers with alarm. Salmon make an extraordinary migration, often hundreds of miles, from inland rivers and lakes where they were born, to the sea, and then back to spawn the next generation. A long-standing network of dams in Western states already makes the journey perilous. Now, with climate change worsening heat waves and droughts, scientists say conditions look grim without intense intervention, which comes with its own risks.

“We are already at critical temperatures three weeks before the most severe warming occurs,” said Don Chapman, a retired fisheries biologist specializing in salmon and rainbow trout, speaking of the conditions. along the Snake River in Washington, where four dams have been the subject of long-standing controversy. “I think we are heading for disaster.

The plight of salmon illustrates a broader danger facing all kinds of species as climate change worsens. Many animals were already struggling to survive due to human activity degrading their habitats. Throw in extreme heat and drought, and their chances of survival decrease.

As an emergency measure, workers at the Idaho Fish and Game agency began capturing a variety of endangered sockeye salmon at the Lower Granite Dam, putting them in a truck and driving them to hatcheries as an interim measure. to decide what to do next. (Idaho hunting officials first attempted to truck the adult fish during a heat wave in 2015. This was done for juvenile salmon on a variety of routes for a variety of reasons.)

In the Central Valley of California, Jonathan Ambrose, a biologist with the National Oceanic and Atmospheric Administration, said he wished he could do something similar. The chinook salmon he watches have always spawned in the mountains. But since Shasta Dam was built over three-quarters of a century ago, they have adapted by spawning right in front of the gigantic structure they cannot cross. The critical issue this year is that the water there is expected to get too hot for the eggs and juveniles. Previous efforts to secure state or federal funding to transport them past the dam have failed.

“We’re looking at maybe 90 percent mortality, maybe even more this year,” Ambrose said.

Elsewhere in California, for the first time since the state built the Iron Gate Fish Hatchery on the Klamath River in 1962 to compensate for lost spawning habitat, state biologists will not release juvenile salmon that ‘they bred in the wild because they probably died. Instead, they spread a million young salmon to other hatcheries in the area that could accommodate them until conditions improve.

“I want to find the positives and there are some, but it’s pretty overwhelming right now,” said Dr. Harley, a marine biologist from the University of British Columbia. “Because if we get too depressed or too overwhelmed, we won’t keep trying. And we have to keep trying.