Days’ search revealed the man’s surfboard, but his body was never found. He was considered Australia’s seventh shark attack victim this year – an alarming tip that has not been seen in the country for 86 years.
“In Australia (this year is) a bit of a blip,” said Culum Brown, a professor at Macquarie University’s Department of Biological Sciences in Sydney. “And in fact, the long-term average is one – one death per year. So seven is far above that, there is no doubt.”
That average of one death a year has been stable for the past 50 years, the Taronga spokesman said.
It is not that there has generally been a sharp increase in shark attacks in Australia ̵
There are a number of possible explanations – several experts have pointed out that the figures for year to year always fluctuate, and this can be simple misfortune. But there is another possible culprit: the climate crisis.
When oceans heat up, entire ecosystems are destroyed and forced to adapt. Fish wander where they have never gone before. The behavior of the species is changing. And as the ocean world transforms, sharks follow their prey and move closer to shores that are popular with humans.
Australia is a hotspot for global warming
On land, Australia’s climate crisis has led to violent bush fires, extreme heat waves and one of the worst droughts recorded.
The Great Barrier Reef, a vital marine ecosystem along the east coast, has experienced such widespread repeated bleaching that more than half of the corals on the reef are dead. Massive stretches of mangrove forests have also died in the last decade.
“These two ecosystems alone are responsible for a massive diversity of marine ecosystems – so you see huge ecosystems disappearing and / or moving,” Brown said.
These types of “marine tropical hikers” often travel up and down the coastline, Brown said, driving on the Eastern Australian Current famously depicted in the movie “Finding Nemo.” But now climate change means the winters are warm enough for these fish to survive the season – so some species are choosing to become permanent in southern waters.
“I spend a lot of time in boats off the coast, and this year I can’t remember a year where I saw so many baitfish aggregations so close to shore,” Brown said. Researchers are still not entirely sure what drives the movement of many of these species – but Brown added, “there is no doubt that sharks are just reacting to where the baitfish are.”
Sharks follow the water temperature
The sea is by no means a stagnant mass; the strong currents mean that there are areas of hot and cold water. The Eastern Australian Current is a major player in this dynamic – it has also grown much stronger in recent decades, meaning it is pumping warmer tropical waters down the coast.
But because the current is more intense, it also pushes cold nutrient-rich water toward some eastern shores.
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 researcher in shark ecology and director of Macquarie’s marine predator research group.
Meanwhile, species such as large whites, which prefer lower temperatures, are drawn closer to the shores, where pockets of cold water also have abundant prey. Tiger sharks are also found further north – but have ventured down to Sydney, probably also affected by the current.
These three species – bull, great white and tiger sharks – are responsible for most of Australia’s deaths from shark attacks.
“I would predict that there will be greater movement, an increase in geographic reach, in many of these species,” Harcourt said. “This is because the dynamics of climate change mean that their habitat in terms of water temperature and prey distribution is also changing. And these animals are large, far-reaching predators.”
“They will potentially come into more contact with humans, and at the same time, human use of the ocean is increasing all the time,” he added.
There are other possible factors
Modern technology, improved medical care, and faster response times mean that the death toll from shark attacks has dropped markedly in the last decade – that’s why this year’s rise is “a real anomaly,” Harcourt said.
But apart from climate change, there may also be other factors that play a role. Happiness is most important: there have been several close calls in recent years where the victim was rescued because there happened to be a medical worker nearby at the time, Brown said.
“We have managed to save more people over the last few years, just by having the fortune of having someone qualified on site to deal with the trauma immediately, and that makes a huge difference,” he added.
It also depends on where the victim is bitten. “An inch to the left if you get bitten on the leg and you can die in at least seconds or minutes,” Harcourt said. “You know, an inch to the right, you’re getting a terrible scar and a lot of pain, but if you do not go into shock, you have a good chance of surviving.”
There is also a chance that people are just spending more time in the water this year because of work from home during the Covid-19 pandemic, or because it has been particularly hot in Australia recently, Harcourt said – increasing the chances they could run into a shark.
We are in a new era of unpredictability
Brown and Harcourt warned that the death toll in 2020 for shark attacks is only based on a single year of data; given shark numbers may fluctuate year by year, it is difficult to say whether climate change is directly causing this year’s increase. It could be a simple matter of mishaps; we just may not know until a few years later when there is enough data to determine if it is a trend or an outlier.
But both experts agreed on one thing: the sea is changing, and sharks are changing with it. Climate change has destroyed the world’s natural environments and thrown everything in balance and disrupted how marine ecosystems live, move and potentially interact with humans.
“You can not draw any conclusions about anything based on (only a year), but there is no doubt that we are moving into a period of the unknown, effectively,” Brown said.
“All the old spreads of species, and how we interact with them – you can pretty much throw it out the window. Whatever comes in the future, it’s going to be new.”