According to CNN, 21 shark attacks on humans in Australia this year have killed seven people, the largest number of deaths since 1934. The surge in deaths from shark attacks has worried experts, with some arguing that the main culprit in the tragedy may be the climate crisis.
One morning in early October, a not uncommon scene appeared on the beaches of Western Australia. A shark attacked a surfer, and then the surfer went missing. Authorities immediately launched a search and rescue operation, and after several days of searching, the man's surfboard was found, but his body has never been found. He was Australia's 7th victim of a shark attack this year, the highest number of deaths from shark attacks in the country in 86 years.
This year's shark attacks have taken place in several Australian states, including Queensland, New South Wales and Tasmania. There were no shark attacks that killed humans in Australia in 2019, and in previous years, there had been only one or two deaths a year.
According to a spokesman for the Tarunga Conservancy of Australia, the last time there were seven shark attack deaths in the country was in 1934, and the highest annual death on record occurred in 1929, when nine people died. Over the past 50 years, the data on an average of 1 person dying per year has remained stable.
Carum Brown, a professor in the Department of Biological Sciences at Macquarie University in Sydney, said: "In Australia, [this year] is a bit overdone. In fact, the long-term average mortality rate is 1 person per year. So there's no doubt that 7 people is much higher than that. ”
This is not to say that shark attacks have increased dramatically in Australia as a whole. There have been 21 shark attacks this year, which is normal and consistent with previous years, with the difference being the mortality rate.
Some experts point out that the numbers fluctuate every year and may just be bad luck this year, but there is another possible culprit: the climate crisis. As the oceans heat up, entire ecosystems are being destroyed, fish are forced to migrate to places they never have been, and species behavior is changing. As the ocean world shifts, sharks are following their prey closer to the coasts humans prefer.
Australia is a hotspot for global warming
On land, Australia's climate crisis has led to raging bushfires, extreme heat waves and the worst drought on record. At the same time, it also causes ocean acidification and temperature rise, causing damage to entire ecosystems. Australia's southeastern region is at the forefront of the climate crisis, where near-surface waters are warming up about four times faster than the global average.
The Great Barrier Reef, an important marine ecosystem off the east coast of Australia, has undergone extensive bleaching, with more than half of the coral reefs dead and large numbers of mangroves also dying over the past decade. Animals are migrating further south in search of a suitable environment. The yellow-tailed maw totoaba, common in tropical waters in the north, is emerging in colonies near Tasmania in the south, the common Sydney octopus has migrated from queensland in the northeast to Tasmania, and even plankton and plants like seaweed are migrating south.
Brown said these "marine tropical nomads" often come and go along the coastline with the famous East Australian currents from the movie "Finding Nemo". But now, climate change means that winters are warm enough for the fish to survive, so some species choose to stay in the southern waters permanently.
Sharks move with the water temperature
The ocean is by no means a stagnant water, and turbulent currents mean areas with warm and cold water. The East Australian Current is a major player in this trend, which has become increasingly powerful in recent decades, injecting more warm tropical waters into the coast, while at the same time pushing nutrient-rich cold waters towards some of the eastern coasts.
These dynamically changing water temperatures may also be the reason why sharks are beginning to enter human space. Robert Harcourt, director of the Marine Predators Research Group at Macquarie University and a researcher in shark ecology, said species like the bull shark prefer warm waters, so they stay longer in warm southern waters. At the same time, species like the great white shark, which prefer lower temperatures, are drawn to the coast, where there are also a large number of prey in cold areas. Tiger sharks usually appear further north, but they also now venture to Sydney, most likely also affected by ocean currents.
These three shark species, bull sharks, great white sharks and tiger sharks, are to blame for the deaths of most shark attacks in Australia.
"I can foresee greater migration and expanded geographical ranges for many shark species," Harcourt said. This is because the dynamic change of climate means that the water temperature and the distribution of prey that they are suitable for habitat are also changing. They may have more contact with humans, and at the same time, human use of the oceans has been increasing. ”
There are other possible factors
Harcourt said the fatality rate of shark attacks has dropped dramatically over the past decade due to modern technological advances, rising medical care and shortened emergency response times, which is why the spike in death rates from shark attacks this year is "a truly anomalous phenomenon."
In addition to climate change, there may be other factors at play. "Luck is a major factor," Brown said. In recent years, there have been several times when the victims have been rescued because there was a medical worker nearby who was able to treat the wound in time. "At the same time, it also depends on where the victim was bitten."
Harcourt said this year may be because people work from home during the COVID-19 pandemic, coupled with Australia's recent particularly hot, people may spend more time in the sea, increasing their chances of encountering sharks.
Climate change is throwing marine ecosystems out of balance
Brown and Harcourt warn that the 2020 shark attack mortality rate is based only on data from a given year, and given that the number fluctuates from year to year, it's hard to say whether climate change directly contributed to this year's surge, or maybe just bad luck. We only have enough data after a few years to know whether this is a trend or an outlier.
But both experts agree on one thing: The oceans are changing, and so are sharks. Climate change is destroying the natural environment and disrupting the way marine ecosystems live, move and interact with humans, throwing everything out of balance.
"You can't draw any conclusions [in just one year], but there's no doubt that we're in a new era of unpredictability," Brown said.
Upstream News Compiled by Ruochen Yang
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