The 2021 heat dome has raised temperatures above 50C along coasts, killing at least a billion sea creatures. That estimate could be 10 times higher, according to one scientist, in a mortality that could change what creatures dominate in the future.
When Chris Harley approached the rugged coast of West Vancouver’s Lighthouse Park, all he remembered was the smell.
“The shore was already dead,” he said.
Flocks of barnacles and starfish baked in the sun. The dark blue and purple mussel shells that underlie a concentrated intertidal life support system had split open – nearly everything was dead.
Beneath the June 2021 heated dome, air temperatures recorded at the nearby lighthouse had soared to 35C. But when the ecologist from the University of British Columbia’s zoology department turned his thermal cameras on the rocks on the shore, readings reached 56°C, well beyond the limit of the shells that inhabit them.
In the next few days, Harley would visit the beaches in the area, at White Rock and Porteau Cove between Vancouver and Squamish. On Galiano Islandhe found a patch of rocky shore the size of a tennis court where at least a million mussels lay dead.
Other scientists and local residents of North Georgia Straight sent him random readings of the shoreline. The results all indicated the same thing: mass mortality.
Ultimately, Harley calculated that the heat wave killed at least a billion sea creatures in the Georgia Straight and Puget Sound.
“I think that’s a pretty healthy understatement. I would say it’s probably 10 times more,” Harley recently told Glacier Media.
The space between high tide and low tide is one of the richest concentrations of life on Pacific Northwest shores. Here, a myriad of seagrass and small creatures create an ecosystem and feeding ground for everything from blue herons and crabs to otters and snails. It even provides shelter at high tide for migrating salmon.
In the nine months since the Heat Dome, Harley joined a group of researchers desperately trying to assess whether the death of so many low-level species would change the balance of the ecosystem.
When he returned to the shores around Victoria – at 10 Mile Point, Saxe Point and up to Sooke – Harley saw a remarkable comeback.
“They seemed pretty normal to me,” he said.
But when he returned to the beaches of White Rock, around Burrard Inlet and Howe Sound, the desolation was clear.
“The bad news is that the recovery is far from complete,” he said. “Last year the Kitsilano spot here in Vancouver with downtown in the background was just algae and mussels in this big field of rocks and now it’s bare rock and barnacles .”
The fact that Canada geese are back is a “silver lining”, he said, as they can facilitate the return of other animal and plant species.
Over the next two or three years, Harley says he hopes the ecosystem will begin to return to its former state. In the long term, it is less secure.
“The questions are: how often is this sort of thing going to happen? How serious is this going to be? ” he said.
According to one study, such a powerful heat wave could hit the coast again as early as the 2040s and return every five to ten years.
One of the effects of mass mortality is that Pacific mussels are expected to take hold. Originally embarking on ships from East Asia more than 100 years ago, oysters were already expected to expand their range and density as temperatures in the ocean are warming due to human-induced climate change. The heat wave, worries Harley, will only accelerate this transformation.
“Things die, it makes way for oysters,” he said. “I think our system is going to turn into this weird stew of things that we’re used to, and things would have appeared across the ocean that just evolved into a warmer climate.”
In other words, he says, the shores of British Columbia could increasingly resemble the subtropical ecosystems of southern Japan, Korea and China.
Die a warning of things to come
It is not only atmospheric heat waves that threaten life in and near the sea.
Direct human impacts, such as overfishing, pollution and habitat destruction, all endanger species on the world’s coasts and deep ocean habitats.
But so is global warming of the oceans and depletion of marine oxygen levels.
And in a study published Thursday in the journal Scienceresearchers have found that if the planet continues on its current trajectory of fossil fuel emissions, mass extinction events could sweep through the world’s oceans by 2300.
As sea creatures face their ecological limits, such mass mortalities would turn into a “great death” equivalent to the extinction at the end of the Permian, a period 250 million years ago when more than two-thirds marine species on the planet have been extinct, discovered. two scientists from Princeton University and the University of Washington in Seattle.
However, reversing the trends in greenhouse gas emissions would reduce the risk of extinction by more than 70%, “by preserving the marine biodiversity accumulated over the past years. [approximately] 50 million years of evolutionary history,” found researchers Justin Penn and Curtis Deutsch.
For Harley, these discoveries — along with the fallout from tragic events like last year’s heat wave — offer anyone who listens or remembers a choice.
“I never encourage weather disasters, but when they do happen, I hope it will serve as a wake-up call,” he said.