As originally reported in The Guardian, our planet's climate crisis is currently pushing great white sharks into new and uncharted waters. This, in turn, is causing local populations of endangered wildlife to plummet.
The world's oceans hit a new record high temperature in 2020, leading young great white sharks to migrate over 600 kilometres north into unfamiliar territory. These waters, found off California's coast, represent a new habitat for the sharks - where temperatures were previously too low to support the species. Since the start of this shift in range, scientists have observed a dramatic rise in the number of sea otters killed by white sharks and a plunge in their population, with the number of otters in Monterey Bay dropping by over 80%.
As temperatures continue to rise, the normal range suitable for great white sharks has shrunk dramatically, forcing these apex predators and their prey to share more common ground, upsetting ecosystems and altering the natural cycle of predation in the region. And, this problem affects more than just sea otters. Salmon fisheries are also at risk, and there is a growing concern over the potential for new and unwelcome encounters between sharks and people, as well.
Scientists hope that drawing attention to the change in habitat of such a high-profile shark will highlight how global heating is affecting our planet's ecosystems. As the equator warms up, more and more marine animals are pushed towards the poles. These changes in the oceans' ecosystems have unpredictable and potentially harmful consequences. Sadly, the shifting of species' ranges is part of a disturbing global phenomenon taking place both above and below water - and the change in white sharks territory is just one example of the broader pattern.
Scientists began studying this specific population of white sharks back in 2014. Their research analysed the relationship between the location of great white sharks and the temperature of the ocean. Using millions of measurements, from monitoring tags placed on the sharks to sightings reported by amateur wildlife watchers, researchers were able to document a dramatic rise in the population of juvenile white sharks in Monterey Bay. This shift appears to have started with a marine heatwave in 2014, and the trend currently shows no sign of slowing.
This spike in north Pacific ocean temperatures lasted from 2014 to 2016 and was nicknamed "the blob" by scientists. In addition to affecting the sharks, this area of warm water eventually developed into a dead zone, harming countless marine animals, causing the death of a million seabirds, and leading to other mass die-offs. Unexpectedly, once the initial heatwave stopped, the white sharks didn't leave. These new predators are able to capitalise on a population of unsuspecting fish, otters, and sea lions.
While the movement of these sharks might seem like a small environmental affair, it likely plays a pivotal role in the region's marine ecosystem. The California coast is now seeing a rapid decline in fish, including salmon, one of the area's most important species. These waters are already under pressure from overfishing, pollution and sound pollution. And, adding a new top predator to the mix will only exacerbate that plight.
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