Why More Extreme Rain Could Mean More Shark Bites

In nan abstraction of conscionable 48 hours this past January, 4 group were bitten by sharks on Australia’s eastbound coast, pinch a 12-year-old boy dying from his injuries. Just 1 time prior, record-setting rainfall soaked nan region. That series of events whitethorn not person been a coincidence: a increasing assemblage of investigation suggests that shark bites, though rare, whitethorn go little truthful arsenic ambiance alteration triggers much dense rainfall events, altering shark behavior.

As pinch immoderate shark bite, it’s intolerable to find nan nonstop drivers down this January cluster, says Charlie Huveneers, head of Flinders University’s Marine and Coastal Research Consortium successful Australia. But nan rainfall, he says, apt contributed: “It mightiness beryllium that because of nan rain, they were much concentrated astatine that time.”

The mentation is that nan deluge, which broke January regular rainfall records for Sydney, flushed sewage and different discarded into nan adjacent coastal waters, attracting baitfish, which successful move lured sharks person to shore. Previous studies successful Australia person shown this correlation, including 1 study that suggests bites from tiger sharks are much common pursuing dense rainfall. Other investigation has recovered that accrued sediment successful water—common pursuing aggravated rain—also raises risks because it reduces h2o visibility, making it much difficult for sharks to spot and debar people.

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Additional factors were apt astatine play successful nan January encounters, Huveneers says, including summertime temperatures that drove group into nan ocean. Bull sharks, nan type believed to beryllium down nan January bites, are besides much communal successful nan section waters during warmer months. “It really goes backmost to this overlap betwixt group and sharks,” he says.

Though utmost rainfall whitethorn not beryllium nan only facet down nan cluster, its apt engagement raises nan mobility of really nan consequence of shark bites mightiness alteration arsenic these events go more predominant and severe globally, including successful nan U.S., wherever shark encounters are reported most. “Extreme rainfall is expected to summation successful wide because a warmer ambiance tin clasp much water,” says John Nielsen-Gammon, a meteorologist astatine Texas A&M University. “And, of course, much utmost rainfall leads to much utmost runoff.”

Figuring retired nan narration betwixt dense rains and shark bites is complicated, though, because there’s a batch we don’t know astir what drives a shark to wound someone, says Catherine Macdonald, head of nan University of Miami’s Shark Research and Conservation Program. What we do cognize is that ambiance alteration is influencing their behavior.

Rising water temperatures are already changing migration patterns, research suggests. One 2022 study search tiger sharks on nan U.S. East Coast recovered that populations complete nan erstwhile decade had progressively shifted north. But different shark type and moreover different individuals wrong type whitethorn respond otherwise to these changes, says shark intelligence Neil Hammerschlag, executive head of nan not-for-profit Shark Research Foundation and nan 2022 study’s lead author. Warmer oceans whitethorn repel immoderate type from coastlines while luring others toward it, he says. And though utmost rainfall whitethorn thief pull baitfish person to shore, nan influx of caller h2o lowers salinity levels, driving immoderate shark type away.

People shouldn’t beryllium afraid, Hammerschlag says, because human-shark encounters are highly rare—you’re statistically much apt to beryllium killed by lightning. Instead beachgoers should beryllium “shark smart” by knowing, for example, erstwhile and wherever definite type are typically astir progressive aliases avoiding swimming astatine dusk and dawn. Proximity doesn’t guarantee interaction, he says, but nan look for immoderate wound requires it. “And immoderate biology information that makes those things hap will summation nan chance of human-shark interaction.”