What If There Were No Sharks?

In fact, gray reef shark forays between coastal waters and the deep sea in the Pacific Ocean's Palmyra Atoll bring the reef more than 200 lbs. (95 kilograms) of nutritious nitrogen per day.

A Murky Future

Approximately 25% of all shark, skate and ray species are currently threatened with extinction, according to the Smithsonian Institution’s Ocean Portal. Because sharks have few babies and are slow to mature, their numbers aren’t replenishing quickly enough to keep up with losses from commercial fishing, Daly-Engel said.

In recent decades, some shark populations have declined by up to 90%, reflecting an unsustainable trend of overexploitation in ocean habitats, according to Bortoluzzi.

“Many species also face the loss of habitats, with refuge areas such as mangroves being destroyed to accommodate our growing human population, and habitats such as seabed and reefs being damaged by destructive fishing methods such as trawling,” Bortolozzi said.

What does the future hold for sharks? Federal legislation and international treaties such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora can help to protect vulnerable populations. But many shark species are poorly understood, which can hinder conservation efforts, said Michael Scholl, CEO of the nonprofit Save Our Seas Foundation.

“Government institutions must have validated information to support significant decline in populations, for example,” Scholl told Live Science in an email. To that end, Save Our Seas works alongside marine researchers to gather shark data that can inform much-needed protective measures; the nonprofit also works to raise public awareness of shark diversity and its importance to their marine ecosystems, Scholl said.

But sharks may be running out of time. And if they were to disappear, the repercussions on ocean food webs would ultimately affect humans, too.

“Fisheries may collapse, with artisanal fishers being the likely most affected, and popular tourism destinations which rely on sharks to attract tourists will also suffer greatly,” Bortoluzzi said.

“It’s important to understand that as much as our oceans need sharks, so do we.”