What is the real cause? Is it climate change, or have humans had other impacts?
Sharks have always been seen as the ocean’s assassins. They are at the top of the food chain, equipped with the traits of cold-blooded predators (such as muscles, sharp teeth, and high swimming speeds).
As frightening as they are, there is a surprising fact: the number of people attacked by sharks each year is not high. Over the past 60 years, there have been just over 2,700 reported shark attacks worldwide, resulting in approximately 439 deaths. In contrast, the number of sharks killed each year reaches… over 100 million (according to Dalhousie University data from 2013), making the figures almost laughable.
In recent years, the number of shark attacks has been increasing rapidly.
However, in recent years, the number of shark attack cases has been rising quickly, especially in North Carolina, USA. Just a few days ago, an 8-year-old boy was attacked by a shark at South Beach (North Carolina), leaving a bite mark on his leg. A week earlier, a young man returned to shore with a “deep bite wound” on his foot after surfing at Ocean Isle Beach.
The most catastrophic incident occurred on June 2, 2019. The victim was a 17-year-old girl named Paige Winters, who almost lost her left leg and two fingers due to a shark attack. She was fortunate to survive thanks to her father, who noticed the situation and rushed in to deliver five punches to the shark’s nose (its weak point) to make it release her.
Paige Winters was saved thanks to her father’s powerful punches.
According to Gavin Naylor, director of the Shark Research Program in Florida, it is difficult to link all three incidents as they involve different shark species. “People often equate sharks as the same species, but that’s not true,” Naylor stated.
He mentioned that the bites on the lower legs might have been from blacktip sharks, a small shark species that is not overly aggressive. In Winters’ case, it was likely a larger predator like a bull shark.
However, according to data from the International Shark Attack File, in recent months, North Carolina has seen more shark attack victims than the total number for all of 2018 combined. This suggests that regardless of the perspective taken, the number of people attacked by sharks is indeed increasing. So, what is the reason?
The warmer the sea, the more sharks?
George Burgess, a former program director, suggests that the cause may be climate change. Warmer sea temperatures will create conditions for more large shark species to thrive, meaning we have more sharks.
“The sea temperatures along the East Coast of the United States are gradually rising, and some species thrive in this environment, especially sharks,” Burgess explained.
Warmer sea temperatures create favorable conditions for sharks to move northward.
Oceans can absorb up to 93% of the heat generated by greenhouse gases on the planet. This significantly impacts the lives of cold-blooded animals like sharks, which rely on their environment to regulate body temperature.
“Climate change is causing the oceans to warm, and the effect is gradually spreading northward,” Burgess noted. This means that shark species are also moving gradually to northern waters.
According to a study published in 2018 in the journal Scientific Reports, predatory sharks like bull sharks are expanding their range northward, including the waters off North Carolina.
The terrain plays a role
The coastal waters of North Carolina are also an excellent habitat for bull sharks, as they have numerous river systems flowing into the ocean.
“Bull sharks are capable of surviving in freshwater environments, which is why they can appear far inland,” he said.
Particularly in brackish waters – where freshwater mixes with seawater, creating a paradise for sharks, as many other fish species inhabit these areas.
“Bull sharks can attack various prey, occasionally including humans. They are large and tend to be quite persistent when attacking.”
More sharks, but the primary reason is still human overpopulation
Excluding the case of Winters, other cases have only resulted in minor injuries. According to Naylor, blacktip sharks are generally not very aggressive. For them, biting a human can be just as surprising as the victim being bitten. Furthermore, these bites are usually not very dangerous.
“These are essentially exploratory bites. They want to understand what the entity in front of them is,” stated Erich Ritter, a shark researcher from Princeton University.
There are more sharks, but the main issue lies in the fact that there are now many more people swimming in the ocean. According to Burgess, the tourism industry in North Carolina’s coastal areas attracts a significant number of visitors each year. With both sharks and humans frequenting the same waters, the chances of encounters inevitably increase.
If you see a school of fish swimming frantically, leave the water immediately.
“The main reason is that the number of people now far exceeds that of 50 years ago. When we coexist in the same waters, we may encounter sharks. If you wave your hand and touch them, they will react, leading to an incident,” he said.
Burgess also mentions that the best way to avoid a shark attack is to immediately leave the water if you see schools of fish panicking. This is a sign that sharks are hunting.
Additionally, a recent study found that great white sharks observe humans swimming or paddling, with movements resembling those of seals and sea lions, their preferred prey.
They researched and compared underwater videos of seals, sea lions, and humans swimming in various ways, using rectangular floats or paddleboards, before drawing conclusions.
Laura Ryan, a postdoctoral researcher in animal sensory systems at Macquarie University’s Neuroscience Laboratory and the lead author, stated: “We attached a GoPro camera to an underwater vehicle and set it to move at the speed of a hunting shark, modeling how great whites perceive the motion and shape of different objects. The results showed that humans swimming, paddling, or surfing resemble seals and sea lions in the eyes of great white sharks. This indicates that great whites may mistake humans for their favorite prey.”
Researchers noted that most shark species are colorblind, meaning colors on surfboards and wetsuits make no difference from the shark’s perspective underwater.
Laura Ryan added: “Understanding why sharks attack humans helps us find ways to prevent these incidents while ensuring the safety of both humans and sharks.”
Moreover, there is another reason that sharks may confuse humans with prey like seals, according to Daniel Abel, a marine science professor at Coastal Carolina University, USA.
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