For years, South Africa’s Seal Island was a bucket-list destination for marine wildlife lovers hoping to witness the breathtaking power of great white sharks leaping from the ocean in pursuit of seals.
But in a troubling turn, the great whites have all but disappeared, as National Geographic detailed — and their absence is sending shockwaves through the entire marine ecosystem.
What’s happening?
A new study from the Shark Research Foundation, built on over 20 years of data and published in Frontiers in Marine Science, revealed just how much the ecosystem around South Africa’s Seal Island has changed since great white sharks began to vanish. The decline started around 2010, but by 2018, the iconic predators had disappeared entirely from the region.
“We saw things that we’d never expect,” marine ecologist and executive director of the Shark Research Foundation Neil Hammerschlag, a coauthor of the study, said.
What followed was a cascade of unexpected shifts, according to the researchers. Without great whites keeping them in check, broadnose sevengill sharks — typically hidden away in nearby kelp forests — surged into the area, sometimes appearing in groups as large as 15. Cape fur seals, once cautious and elusive, began to raft in bold, floating clusters and even chase after cage-diving bait.
These changes marked more than just strange new behavior. They signaled a dramatic reshuffling of the food web — one that researchers never expected to witness firsthand.
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Why is this concerning?
Great white sharks play a crucial role in maintaining ocean balance. As apex predators, they keep populations of other species in check — removing the sick and weak, thereby maintaining healthy food webs. When they disappear, ripple effects follow.
With fewer sharks to keep them in check, seals and sevengills increased — but their own prey populations, including anchovies, Cape horse mackerel, and other smaller sharks, plummeted. This domino effect shows what scientists call a “trophic cascade” — when the loss of a top predator causes dramatic changes at every level of the food chain.
And while the exact reason for the sharks’ disappearance isn’t crystal clear, the finger points toward both human and natural threats. Killer whales may be targeting them, but shark nets — which kill up to 30 great whites a year — likely contribute to the decline. Because these sharks reproduce slowly and mature late, even small losses can have major consequences.
What’s being done about it?
Experts like Hammerschlag say it’s time to rethink how we protect both people and predators. One major change? Ending outdated netting programs and adopting non-lethal beach safety measures, such as shark spotters and electronic deterrents.
On the individual level, supporting shark conservation groups and marine policy reforms is one way to help. You can also check out organizations like the Shark Research Foundation and follow science-backed efforts to reduce harmful fishing practices.
As Hammerschlag put it: “We can’t stop the orcas. But we can stop the nets.” And doing so might just help restore balance to a fragile underwater world.
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