Rare sharks are vanishing fast - can they still be saved?

For over 400 million years, sharks have ruled the oceans, surviving mass extinctions and shifting climates. But right now, they’re facing something they may not survive – human pressure.

Overfishing, pollution, and habitat loss have pushed about one-third of the 500 known shark species to the brink of extinction. That’s bad news for the oceans – and for us.

The sharks with the greatest risk of extinction aren’t just the ones we’ve heard of, like great whites or hammerheads.

According to a new study, it’s the unusual species that face the greatest risk – the ones that patrol the deep seafloor, or the specialists with narrow diets and unique habits.
If they vanish, we lose more than species names. We lose entire sets of traits, behaviors, and ecological roles that no other creatures can fill.

Rare sharks are the most at risk

The findings come from researchers at Stanford University who looked closely at a group of sharks called Carcharhinus.

This genus includes 35 species, many of which are either “Vulnerable,” “Endangered,” or “Critically Endangered” according to the International Union for Conservation of Nature.

Among the most threatened are the bull shark and the oceanic whitetip – both powerful predators.

Unusual sharks could vanish

To understand which sharks are most at risk and why, the researchers analyzed over 1,200 fossil and modern teeth from 30 species.

Shark teeth reveal much of the story – their size offers clues about the animal’s overall bulk, while their shape exposes what kind of prey they preferred.

By looking at this data, the scientists found a pattern: sharks with unusual body types and diets are more likely to go extinct than the “average” ones.

Why this matters for the ocean

Sharks that grow bigger than average need a lot of food to survive, so they’re more vulnerable when prey becomes scarce.

Sharks with specialized diets or strange body features that fit specific environments – like shallow coasts or deep trenches – don’t adapt easily when those environments are damaged or overfished.

That means the survivors are more likely to be medium-sized, generalist sharks living in the middle of the ocean.

“Our study illustrates that if these major shark extinctions do happen, sharks will become more alike and simplified, and you end up with a more boring world with less diversity of forms,” said Mohamad Bazzi, a postdoctoral scholar in the Stanford Doerr School of Sustainability.

“Even small differences between species matter. They each bring something distinct and important.”

Losing rare sharks and their uniqueness

This loss of uniqueness isn’t just about looks. It affects how entire ecosystems function. In other parts of nature, when specialist species vanish, big problems follow.

When vultures declined in South Asia, for example, it led to increases in disease and scavenger species that disrupted human communities.

When sea urchins exploded in numbers due to a drop in predators, coral reefs suffered, and fisheries took a hit.

“This broader erosion of unique shark morphologies would mean that many distinctive features of each species, and the functions that they have in a given ecosystem, would go away,” said Jonathan Payne, a professor of Earth and planetary sciences at Stanford.

Shark traits that can’t be replaced

The concern goes beyond just aesthetics or ocean health. Some of the traits we might lose – body structures, resistance to disease, unique hunting strategies – could inspire new technologies or medicines.

Nature has often been a powerful teacher. When we cut off that possibility, we don’t just lose animals – we lose knowledge.

“With this huge loss of shark traits, humans would be undoing all of this evolutionary work that’s gone on for millions and millions of years,” said Payne.

“When we undo all of this work, we’re not only losing things that give us joy, but we’re also losing potential practical evolutionary solutions to problems, such as disease treatments or insights into new materials. We lose in basically every way when we drive species extinct.”

An ongoing pattern of extinction

The study adds to a growing pile of evidence that extinction tends to leave behind “average” species while wiping out the rare and unusual.

This pattern, called phenotypic homogenization, has been seen in birds, reptiles, and even plants. It flattens the natural world into something simpler, and often weaker.

But there’s still time to change course. The biggest threat to sharks – overfishing – is something we can control.

Other threats like habitat loss and pollution play a role, but ending the killing of sharks for their meat, fins, and as bycatch would make the biggest difference.

We can still save rare sharks

We’ve saved species before – we can save sharks too. Take the northern elephant seal. In the 1800s, hunters wiped them out almost entirely for their blubber.

Only about 20 seals were left by the time hunting was banned. Today, there are around 150,000 living along the West Coast, playing vital roles in the marine ecosystem.

“People don’t need to think about conservation of species as something theoretical, where if we make this change, only our great-great-grandkids might see a different world,” said Payne.

“Over the course of just a few decades for some of these threatened sharks, you could already see positive change.”

If we stop overfishing now, the oceans could still keep their weird, wonderful sharks – and all the benefits they bring with them.

The full study was published in the journal Science Advances.

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