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– Even before the ocean caught fever and reached temperatures no one had ever seen, Australia’s ancient giant kelp was cooked.

Rodney Dillon noticed the day he squeezed into a wet suit several years ago and dove into Trumpeter Bay to catch his favorite food, a big sea snail called abalone. As he swam amid the towering kelp forest, he saw that “it had gone slimy.” He scrambled out of the water and called a scientist at the University of Tasmania in nearby Hobart. “I said, ‘Mate, all our kelp’s dying, and you need to come down here and have a look.’

“But no one could do anything about it.”

Climate change had arrived at this island near the bottom of the world, and the giant kelp that flourished in its cold waters was among the first things to go.

Over recent decades, the rate of ocean warming off Tasmania, Australia’s southernmost state and a gateway to the South Pole, has climbed to nearly four times the global average, oceanographers say.

More than 95% of the giant kelp — a living high-rise of 30-foot stalks that served as a habitat for some of the rarest marine creatures in the world — died.

Giant kelp had stretched the length of Tasmania’s rocky east coast throughout recorded history. Now it clings to a tiny patch near Southport, the island’s southern tip, where the water is colder.

“This is a hot spot,” said Neil Holbrook, a professor who researches ocean warming at the Institute for Marine and Antarctic Studies at the University of Tasmania. “And it’s one of the big ones.”

Climate scientists say it’s essential to hold global temperatures to 2.7 degrees Fahrenheit (1.5 degrees Celsius) above preindustrial times to avoid irreversible damage from warming.

The Tasman Sea is already well above that threshold.

A stretch of the sea along Tasmania’s eastern coast has already warmed by nearly 3.6 degrees Fahrenheit (2 degrees Celsius), according to ocean temperature data from the Hadley Center, the U.K. government research agency on climate change.

As the marine heat rises and the kelp simmers into goo, Dillon and other descendants of Tasmania’s first people are losing a connection to the ocean that has defined their culture for millennia.

Aboriginals walked to present-day Tasmania 40,000 years ago during the Stone Age, long before rising sea levels turned the former peninsula into an island.

Cut off from Aboriginals on the mainland, about a dozen nomadic tribes were the first humans to live so close to the end of the Earth, fishing amid the giant kelp for abalone, hunting kangaroo and mutton birds, turning bull kelp into tools, and fashioning pearlescent snail shells into jewelry for hundreds of generations.

But that was before British colonizers took their land and deployed an apartheid-like system to wipe them out.

Now, as descendants try to get full recognition as the first people and original owners of Tasmania, climate change is threatening to remove the marine life that makes so much of their culture special.

The warming waters off Tasmania are not just killing the giant kelp, but transforming life for marine animals.

Warm-water species are swimming south to places where they could not have survived a few years ago. Kingfish, sea urchins, zooplankton and even microbes from the warmer north near the mainland now occupy waters closer to the South Pole.

“There’s about 60 or 70 species of fish that now have established populations in Tasmania that used not to be here,” said Craig Johnson, who leads the ecology and biodiversity center at the Institute for Marine and Antarctic Studies. “You might see them occasionally as sort of vagrants, but they certainly did not have established populations.”

But the region’s indigenous cold-water species have no place to go. Animals such as the prehistoric-looking red handfish are accustomed to the frigid water closer to the shore. They cannot live in the deep-water abyss between the tip of Tasmania and Antarctica.

“It’s a geographic climate trap,” Johnson said. Marine animals unique to Australia — the wallabies and koalas of the deep — could easily vanish. “So there’s going to be a whole bunch of species here that we expect will just go extinct. You know, it’s not a happy story.”

In 1950, giant kelp stretched over 9 million square meters in a thick band along Tasmania’s coast, said Cayne Layton, a research fellow at the marine and Antarctic institute. Today, it covers fewer than 500,000 meters in little spots on the coastline.

Giant kelp needs cool, clean, nutrient-rich water to survive, and it’s losing all three.

It is a serious loss. Divers coveted swimming amid plants that grew like the mythical beanstalk to glimpse some of the world’s rarest creatures. Squid fed there, red handfish hid there, spiny pipehorse lounged about, and rock lobster were abundant.

The most recent study — nearly 10 years old — estimated that 95% of giant kelp had been lost to warming and pollution, Layton said, and the problem is probably much worse now.

The less spectacular common kelp, which grows on the coastal slope leading to deep water, is overtaking the spaces where giant kelp grew, Layton said. Along with long, straplike bull kelp that clings to giant rocks near the shore, common kelp appears to be more tolerant to warming temperatures.

But even these species aren’t safe. The warming water has introduced a new plague: long-spine sea urchins, an animal that greedily devours kelp.

A single urchin was found in the cold waters off Tasmania by divers conducting a survey in 1978. Now, there are more than 18 million, according to the most recent survey by the Institute for Marine and Antarctic Studies.

Sea urchins prefer warm water. They swarm rocky reefs where kelp grows, leaving oceans barren and devoid of life.

Kelp forests’ “importance is equal to forests on land,” said Layton, “so if you can imagine what the world would be like without trees, that’s what a world without kelp forests would be like.”

Scientists say there is only one explanation for why sea urchins migrated so far from their warmer natural habitat near Sydney to the cold waters around Tasmania: the East Australian Current.

The current, made famous in the film “Finding Nemo,” is fed by a vast stream of tropical water that reaches Australia’s coast after traveling all the way from South America. The water then flows south down the east coast of Australia and then swings back east just north of Sydney.

At that point, the warm-water current splits, with some water flowing southward toward the Tasman Sea in the form of swirls of tropical water called eddies — and this secondary branch has intensified.

This extension of the East Australian Current is spewing thousands of eddies deeper southward toward Tasmania, carrying the larvae of warm-water species to places they had never been.

According to research compiled by Prof. Gretta Pecl at the University of Tasmania, toxic algae blooms lurk where giant kelp once flourished. Abalone have gone from healthy to “stressed.” The brightly colored Maori octopus is being replaced by the gloomy octopus, more common to the waters near Sydney. And a yellow-bellied sea snake has migrated to the habitat.

The warmer water disintegrated most of the giant kelp over two decades and contributed to a record-breaking marine heat wave in 2015.

“You can’t say that this event was due to climate change,” said Holbrook, the ocean scientist. “But what you can say is that the intensity was much more likely due to climate change.

“You liken it to smoking,” he said. “If you smoke cigarettes, you increase the likelihood of getting lung cancer.”

The marine heat wave left something behind when it finally ended: disease.

A sickening smell at the shallow Pipe Clay Lagoon is how Pacific oyster mortality syndrome introduced itself to Steve Calvert.

The syndrome, known as POMS, turned his small oyster farm in the lagoon into a mass grave, and the smell of the dead stretched for miles. Calvert lost 75% of his oysters in 2016.

Oyster mortality disease had stricken France, China, the United States, New Zealand and even Sydney, but never pristine Tasmania.

“We’ve got a reputation in Tasmania of having pure water and some of the freshest air in the world,” said Calvert’s son, Liam, a manager at the farm. “So that’s part of why there’s an attraction to the Tasmanian oyster, because people think pristine-forest freshness and all that kind of thing.”

In an encouraging sign that Tasmania’s aquaculture can adapt, scientists had prepared the Calverts and other farmers for the possibility that POMS would strike.

“We’ve been working with industry for quite a long time, and we’ve always had the philosophy that scientists need to know how to farm and farmers need to know how to do science,” said Sarah Ugalde, a research fellow at the University of Tasmania.

Ugalde and her team persuaded the farmers to buy oysters from other areas that survived a disease outbreak. They used that stock to cultivate a disease-tolerant oyster. The Calverts lost about a million oysters but rebuilt the stock with spat — oyster babies — recommended by scientists.

Tasmania’s $25-million-per-year oyster farming industry is thriving. The product price, driven up to $1 per oyster from demand during the disaster, stayed the same, helping the Calverts to increase revenue.

“It’s good performance work, and there’s a good return for the hard work,” Steve Calvert said. “We still love this ocean.”

It’s a matter of adapting to a warming world.

“For southeastern Tasmania, which accounts for most of Australia’s fishery production, the projections are that the fishery production will decline,” said Johnson, the marine institute researcher.

“Like I said, it’s not a particularly happy story.”