Experts Believe Spike in Shark Attack Deaths May be Caused by Climate Change


Image: ANDY CASAGRANDE / CORAL REEF IMAGE BANK

by Amy Lupica, ODP Contributing Writer 

Sharks have killed seven people in Australia in 2020, the most since 1934, and scientists believe climate change might be responsible. According to the Taronga Conservation Society Australia, for the past 50 years, the average number of yearly shark attack fatalities was one. Despite the total number of shark attacks not increasing significantly, experts worry that fatalities will increase as warming waters and devastated ecosystems change animal behavior.

Why This Matters: Australia’s ocean is warming at an alarming rate. The waters along the southeastern coast are warming four times faster than the global average. In the past 25 years, half of the coral in the Great Barrier Reef has been wiped out due to rising temperatures and overexposure to direct sunlight, a process called “bleaching.” The loss of these corals and the simultaneous decline of large stretches of mangrove forests, has had devastating consequences for marine life in the region

Without habitats, sea life has begun mass migrating south toward Tasmania and staying there longer due to warming winter temperatures. Many of the species migrating are bait fish, leading both locals and experts to believe that the sharks are following their food, leading them into areas where conflict with humans is more common. These developments raise questions about how other species will adapt to warming temperatures and the impact it may have on fishing, trade, and daily life.

Push and Pull Factors: Warming ocean temperatures and ocean stratification have been found to affect the strength of currents. One major current in the Pacific, the Eastern Australian Current, has grown stronger with warming temperatures and is now pumping warmer waters south, and cooler more nutrient-rich waters toward eastern shorelines. The nutrient-rich waters attract bait fish, and sharks, to human territory. 

Bull sharks, which prefer warmer water, have begun to move further south, but great whites and tiger sharks have made their way into cool pockets of water near shorelines occupied by humans. These three species are responsible for most shark attack fatalities in Australia. Experts believe that shifts in the geographic range of marine life will continue as global temperatures rise. Robert Harcourt, a researcher of shark ecology said, “I would foresee that there’s going to be greater movement, an increase in geographic range, in a lot of these species. That’s because the dynamics of climate change mean their suitable habitat in terms of water temperature and prey distribution is changing as well. And these animals are large, far-ranging apex predators.”

Confounding Variables: Increased fatalities may also be explained by other factors. Experts agree that chance plays a primary role in whether or not an injury becomes fatal. 

Culum Brown, a professor at Macquarie University’s Department of Biological Sciences, recalls several recent instances in which victims were saved because medical professionals simply happened to be nearby. Harcourt also notes the picky nature of shark attack injuries, “one centimeter to the left, if you get bitten on the leg, and you can die in seconds or minutes at least,” he said. “one centimeter to the right, you get a terrible scar and a lot of pain but if you don’t go into shock you’ve got a good chance of survival.” One year of anomalous data, they say, isn’t enough to know what exactly is causing the spike.

Both experts agree, however, that as the ocean changes, so will animal behavior. Brown explained, “all the old distributions of species and how we interact with them — you can pretty much throw that out the window. Whatever coming in the future is going to be new.”

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