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A woman died after a great white shark bit her off the coast of Maine two weeks ago. It was the state's first shark fatality ever.
Some experts say warming waters along the East Coast may lead some shark species to expand their ranges northward.
Multiple beaches in Cape Cod, Massachusetts, also closed last week after great white sightings.
Shark researchers say great whites are attracted to Cape Cod because of its growing population of seals — the predators' favorite food.
A great white shark bit Julie Dimperio Holowach off the coast of Maine's Bailey Island late last month. She died before paramedics arrived, making the event the state's first fatal shark attack.
The tragedy prompted questions about why a great white might swim so far north.
Although these sharks have occupied waters off of Maine and northern Canada for thousands of years, one trend may increase the likelihood of unfortunate encounters: Oceans are heating up.
"Global climate change has prompted warmer water temperatures farther northward," George Burgess, former director of the Florida Program for Shark Research, told Business Insider. That leads more members of cold-water-loving species, like great whites, to travel farther up, where water is cooler.
That could mean more fin sightings — and possibly attacks.
Great whites will be "found more commonly in Maine waters in the years ahead," Burgess predicted.
Warming waters may mean more sharks farther north
According to Burgess, between 15 and 20 shark species swim in East Coast waters.
"Of those, perhaps only six or seven of them are potentially dangerous to humans in the sense of being biters," he said.
Sharks rely on the water temperature to regulate their body heat. But oceans absorb 93% of the excess heat trapped on the planet by greenhouse gases. The year 2018 was the hottest on record for the world's oceans, and that change impacts the ranges of marine animals.
"I think it is highly likely that warming waters will result in the northward movement of sharks in the Northern Hemisphere that were previously restricted to more southern latitudes," Gavin Naylor, the current director of the Florida Program for Shark Research, told Business Insider via email.
"We have incontrovertible data that show these kinds of patterns in Australian waters," he added.
Not all sharks like their water to be the same temperature. Bull, tiger, dusky, spinner, silky, and black-tipped sharks all prefer warm, tropical waves and are typically responsible for attacks in Florida and the Carolinas.
But as ocean waters heat up, more areas are becoming hospitable to those shark populations.
"Their distribution has widely increased beyond the southeast US," Burgess said, adding, "those species found in warmer waters will now proceed all the way up to southern New England in the summer."
Great whites, by contrast, like frigid oceans.
"For white sharks, the total area occupied by them probably won't change, but where that area is will change — it'll shift farther north," Burgess said.
Still, Naylor cautioned that one fatal attack does not constitute a trend in a particular region.
"While the fatality in Maine was the first we have on record, it should not be taken to mean that white sharks are 'moving in to the area,'" he said, adding, "white sharks have been in the waters off Maine (and most of the North Atlantic) for thousands of years."
Growing seal populations are fueling shark encounters in Cape Cod
Warming waters aren't the only reason for an increase in human-shark encounters, though.
In Massachusetts, the presence of more great whites is likely a consequence of ballooning populations of grey and harbor seals, Burgess said.
Last week, officials closed several beaches in Truro, Wellfleet, Eastham, and Orleans, Massachusetts for swimming due to a great white sighting off shore, the Boston Globe reported.
Seals have flourished since the passage of the Marine Mammal Act in 1972, which protects them and other sea creatures from hunting and human interference.
"In the 50 years since, we've seen a recovery of those mammals. What that means for New England, though, is colonies of seals along Cape Cod beaches — seals that white sharks come close to shore to eat," Burgess said.
Sharks, too, are protected, so their populations are also increasing along the East Coast.
"More people, more seals, and more sharks in concentrated areas like Cape Cod is bound to result in conflict of interest," Burgess said, adding, "our playground is the sharks' dining room."
"Sharks follow their food," he said.
However, your odds of being bitten by a shark are about 1 in 4 million, according to the International Wildlife Museum. We're not the predators' preferred meal, so if a shark bites a human, it's typically an exploratory nibble.
"The shark is trying to figure out what we could be," Ritter said.
Read the original article on Business Insider