Sharks have killed 7 people in Australia this year, the most since 1934. Climate change could be a factor

Days of search uncovered the man’s surfboard, but his body was never found. He was counted as Australia’s seventh victim of a shark attack that year – an alarming spike that has not been seen in the country in 86 years.

“There’s been a little slip in Australia (this year),” said Culum Brown, professor in the Department of Biological Sciences at Macquarie University in Sydney. “In fact, the long-term average is one – one death per year. So seven is way beyond that, there’s no doubt about it.”

The average of one death per year has remained stable over the past 50 years, the Taronga spokesman said.

It’s not that shark attacks in Australia have increased significantly overall – there have been 21 shark incidents this year, which is normal and in line with previous years. The difference is in the death rate.

There are a number of possible explanations – several experts have suggested that the numbers fluctuate from year to year and this could just be bad luck. But there is another possible culprit: the climate crisis.

As the oceans warm up, entire ecosystems are being destroyed and have to adapt. Fish migrate where they have never been before. The behavior of the species is changing. And as the marine world changes, sharks follow their prey and approach the shores popular with humans.

Australia is a hotspot for global warming

On land, Australia’s climate crisis has resulted in raging bush fires, extreme heat waves and one of the worst droughts of all time.

But it has also inundated the oceans with acidification and rising temperatures, which can destroy entire ecosystems. The south-eastern region of Australia in particular is at the forefront of the climate crisis – near-surface waters are warming around four times the global average.

The Great Barrier Reef, a vital marine ecosystem along the east coast, has been repeatedly bleached so frequently that more than half of the corals on the reef are dead. In the past decade, huge mangrove forests have also died.

“These two ecosystems alone are responsible for a massive variety of marine ecosystems. So you see huge ecosystems disappear and / or move,” Brown said.

All of this means that animals migrate further south than normal in search of a suitable environment. Species like yellowtail kingfish, which are typically found in northern tropical waters, are found in flocks near the southern island state of Tasmania. The common Sydney octopus has relocated to Tasmania from the northeastern state of Queensland. Even plankton and plants like seaweed move south.

These types of “tropical marine animals” often travel up and down the coast, Brown said, riding the Eastern Australian Current, famous in the movie “Finding Nemo.” But now climate change means winters are warm enough for these fish to survive the season. Some species therefore choose to stay in the southern waters permanently.

“I spend a lot of time in boats offshore and this year I don’t remember a year I’ve seen so many baitfish populations so close to shore,” said Brown. Researchers are still not entirely sure what drives the movement of many of these species – but Brown added, “There’s no doubt that the sharks are only responding to where the baitfish are.”

Sharks follow the water temperature

The ocean is by no means a stagnant mass; Due to the strong currents, there are areas with hot and cold water. The Eastern Australian Current plays an important role in this dynamic – it has also gotten much stronger over the past few decades, meaning it is pumping more warm tropical water along the coast.

But because the current is more intense, it also pushes cold, nutrient-rich water against some east bank.

These dynamic, changing water temperatures may also be the reason why sharks begin to move into human spaces. Some species, like bull sharks, like warm water – so they spend more time in the warm southern waters, said Robert Harcourt, a shark ecology researcher and director of Macquarie’s marine predator research group.

Meanwhile, species like whites, which prefer lower temperatures, are being drawn closer to the coast, where pockets of cold water also hold abundant prey. Tiger sharks are also usually found further north – but have ventured as far as Sydney, probably also affected by the current.

These three species – bull, white and tiger sharks – are responsible for most of the deaths from shark attacks in Australia.

“I would anticipate that there will be greater movement and geographic range for many of these species,” said Harcourt. “This is because the dynamics of climate change also change the suitable habitat in terms of water temperature and prey distribution. And these animals are large, far-reaching apex predators.”

“You will potentially come into more contact with humans, and at the same time human use of the ocean is constantly increasing,” he added.

There are other possible factors

Modern technology, improved medical care and faster emergency response times mean the death rate from shark attacks has fallen significantly over the past decade – which is why this year’s increase is “a real anomaly,” Harcourt said.

Apart from climate change, other factors could also play a role. Happiness matters: there have been several close calls in the past few years where the victim was saved because a medical worker happened to be around at the time, Brown said.

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“We’ve saved several people over the past few years just by being lucky enough to have someone on the spot who qualifies immediately for the trauma, and that makes a huge difference,” he added.

It also depends on where the victim is bitten. “An inch to the left if your leg is bitten and can die in at least seconds or minutes,” said Harcourt. “You know, an inch to the right gives you a terrible scar and a lot of pain, but if you don’t go into shock, you have a good chance of survival.”

There’s also a chance people will be spending more time in the water this year because they are working from home during the Covid-19 pandemic or because it has been particularly hot in Australia recently, Harcourt said – what the odds increases that they might have run into a shark.

We are in a new era of unpredictability

Brown and Harcourt warned that the 2020 death rate from shark attacks is based only on a single year of data. Given that shark numbers can fluctuate from year to year, it’s difficult to say whether climate change is directly causing this year’s increase. It could be a simple bad luck thing; We can’t know until a few years later when there’s enough data to determine if it’s a trend or an outlier.

However, both experts agreed: the ocean is changing and the sharks are changing with it. Climate change has devastated and unbalanced the world’s natural environment, disrupting the life, movement, and potential interaction of marine ecosystems with humans.

“You can’t infer anything based on (just a year), but there is no doubt that we are effectively entering a time of the unknown,” Brown said.

“All the old species distributions and how we deal with them – you can pretty much throw that out the window. Whatever comes in the future will be new.”