In 2011, underwater temperatures shot up by two degrees Celsius in Western Australian waters — and stayed that way, well above normal, for a staggering 10 weeks.
This punishing heatwave changed the ecosystem for good.
Returning five years later, scientists found that 100 kilometers of kelp forests had been wiped out — replaced by tropical and subtropical fish, seaweed, and coral.
They don’t expect the kelp to return.
It’s now clear: Climate change is happening as much below the waves as above.
A new study in Nature Communications finds that marine heatwaves have been increasing sharply over the last century.
Comparing data from two periods — 1925-1954 and 1987-2016 — the study found heatwaves jumped by 34 percent in frequency.
And the duration of heatwaves (number of days per year where underwater temperatures reached high extremes) more than doubled.
Finally, the studied showed that intense heating had spread geographically, extending across 65 percent of the ocean’s surface.
Less than a hundred years ago, it was common for regions of the sea to go a full year without experiencing a heatwave.
Now, the opposite is true: at any particular place, marine heatwaves happen each year more often than not.
This isn’t just bad news for kelp forests, but also for many other ecosystems and species, and for people who depend on the oceans for their livelihoods.
Perhaps of greatest concern is the world’s coral reefs—bastions of biodiversity, the tropical rainforests of the ocean.
Reefs have evolved to survive within certain temperature ranges. But now, the best available evidence—based on massive data-sets and analyses published in the world’s most rigorous scientific journals—suggests we’re blowing right past those thermal limits.
When the waters around coral reefs become too warm, the coral expel their symbiotic algae (called “zooxanthellae”), which normally feed the coral via photosynthesis.
With their algae gone, the coral turns ghostly white—a phenomenon known as “coral bleaching”.
If the heat wave lingers over weeks or months, the corals and their algae can’t recover, and the corals and the reefs perish.
Hit with a double dose of hot temperatures in 2016 and 2017, Australia’s Great Barrier Reef experienced its worst coral bleaching to date.
These heat waves were linked directly to global warming, based on an exhaustive battery of statistical analyses.
The upshot: Nearly a third (29 percent) of the Great Barrier Reef has been decimated by overheating in just the past two years.
BIG FAIL FOR POLITICAL CONSERVATIVES
Although the calamity on the iconic Great Barrier Reef was global news, the Australian government is failing to protect its seas at every turn.
Australia is, on a per-capita basis, among the very worst carbon polluters in the world—and also sells huge amounts of coal to China, India, and other big-polluting nations.
Hence, when it comes to global warming, Australia is part of the problem, not part of the solution.
The political conservatives currently running Australia get their marching orders and most of their donations from the country’s massive coal, gas, and mining industries.
And if being one of the world’s worst polluters isn’t bad enough, the Australian government has also recommended cutting its marine sanctuaries by half.
Indeed, if the current rightwing government has its way, 76 percent of the Coral Sea, home to the Great Barrier Reef, would be opened up to commercial fishing and trawling, practices that are notoriously damaging to marine life.
How much more wrong-headed can things be?
A MESSAGE TO REMEMBER
Many people in the world, including ALERT scientists, see things like this:
The next time they go to the voting booth, Australians need to remember the shocking trends and dire warnings revealed by long-term scientific studies of their seas and the global environment.
Among many things, Australians are renowned for their heartfelt saying: “Do the right thing.”
The world is watching, Australia.
It’s time to do the right thing.