What would happen if sharks went extinct?

Sharks are the ocean’s most fearsome creatures—if Hollywood has anything to say about it. Movies like Jaws, the Meg, and Deep Blue Sea have elevated the great white to international infamy—but in reality more than 100 million sharks are killed by us every year. There are more than 500 different shark species alive today, each in charge of protectinging their delicate marine ecosystems and keeping our oceans healthy and biodiverse. New species are still being discovered all the time. 

Sharks are a diverse group, coming in all different shapes, sizes, and some are even known to live for hundreds of years. Sharks have been a vital part of our world and its processes for more than 450 million years—that’s around 90 million more years than trees and 190 million years before the dinosaurs. Yet for the first time in all those years, around one third of all chondrichthyans* species (sharks and their relatives) are severely threatened from overfishing, accidental bycatch and habitat loss. 

But why should we care? What would really happen if all sharks disappeared? How would an extinction that dramatically impact our oceans, world, and us?

The Current State of Global Shark Populations

Quick Facts:

• Since 1970, we have lost 71.1% of sharks and rays.
• Faster-swimming species, such as hammerheads and requiem sharks, have been particularly affected.
• Humans are killing sharks at a much faster rate than sharks can repopulate.
• Despite regulations, shark mortality rates remain high globally, particularly in areas where destructive fishing methods like gillnets and trawls are used.
• Sharks are keystone species, and play a crucial role in maintaining the health of marine ecosystems.

Of all the known shark and ray species, more than one third are now classified as endangered or critically endangered on the IUCN Red List of Threatened Species. Among the sharks on the IUCN Red List are the Great hammerhead (Sphyrna mokarran), the Basking shark (Cetorhinus maximus), the Sand tiger shark (Carcharias taurus), and the Oceanic whitetip (Carcharhinus longimanus). Sharks and rays now rank second among vertebrates (after amphibians) in terms of extinction threat. 

Even more devastatingly, some scientists have concluded that we have already lost a handful of important species. The Lost shark (Carcharhinus obsoletus), Java Stingaree (Urolophus javanicus), and Red Sea Torpedo (Torpedo suessi) have not been recorded for over 80 years, which leads scientists to believe that they have gone extinct. These probable extinctions are some of the first to come as a direct result of overfishing our oceans. 

Why are so many shark species endangered?

The state of the world’s shark populations is the result of overfishing. Our love of ocean bounty has driven many species of shark to the brink of extinction. Especially fast oceanic species like hammerheads and whitetips often get accidentally caught  in commercial nets. This is called bycatch, and kills around 100 million sharks per year. 

Overfishing

Overfishing refers to the process of catching fish faster than they’re able to reproduce, leading to a steady decline in fish populations. This practice is particularly detrimental to sharks due to their slow growth, late maturity, and low reproductive rates. Destructive fishing methods like gillnets and trawling are particularly harmful. 

However, the depletion of shark populations isn’t just accidental. The value of shark products worldwide is nearly $1 billion traded per year. Shark fins and shark meat are the most sought after, used in soups and other delicacies around the world. In some cases, sharks caught as in bycatch are kept for their meat and fins. 

Bycatch

Bycatch is closely linked to overfishing. Popular seafood like tuna, mackerel, swordfish, and other pelagic fish are sought out by thousands of commercial fishing nets every day. This means we end up indiscriminately capturing millions of species. Alongside sharks, other victims of bycatch include sea birds, sea turtles, juvenile fish, and cetaceans*. Evolving fishing technology like Fish Aggregating Devices (FADs)*, giant purse seine nets*, and illegal driftnet fishing* which are designed to increase catch volume all contribute to the problem.

Habitat loss

Habitat loss is another problem for shark populations, especially those that rely on coastal habitats like mangroves, kelp forests and reef systems. These habitats are important feeding and nursing grounds for baby sharks and rays, providing safety and shelter from predators. But reef ecosystems are particularly vulnerable right now, as they’re under threat from ocean plastic, pollution, and mass tourism. 

Policy

While bycatch, overfishing, and ocean pollutants have the most direct impact, these problems are exacerbated by inactivity and lack of shark protection policies. One example is the case of the oceanic whitetip. This shark was once one of the most common sharks in the open ocean, but it is now among the most threatened. This is partly because the regional fisheries management organizations (RFMOs) have failed to fully address the shark’s decline. Despite laws like the 2010 Shark Conservation Act, which prohibits finning, and the creation of ‘shark sanctuaries’ in places like the Maldives, much still needs to be done to help shark populations recover from the last 50 years of exploitation.

What would happen if sharks went extinct?

Ecosystems are built on the balance of relationships between organisms. These relationships play a crucial role in supporting all life on Earth. When certain species in an ecosystem starts to disappear, it creates a ripple effect that impacts all the parts of the ecosystem, making it unstable. and in the worst case, causing a trophic cascade* that can lead to mass extinction. This is why abundant and varied biodiversity is so important—with keystone species like sharks playing a crucial role in keeping ecosystems healthy.

If all the world’s sharks went extinct, planet Earth would go through several major irreversible changes that would deeply impact us and our oceans. Sharks are top predators, so the first thing we would notice is a population explosion in their prey. Fish, seals, seabirds, and other sea creatures would overwhelm our oceans, causing massive biological imbalance. Their overpopulation would deplete resources further down the food chain, creating what is known as a trophic cascade and cause long term damage to ecosystems.

Without sharks to keep fish and sealife populations in check, disease and competition for resources would increase, which could deplete populations further. Some sharks are vital for maintaining healthy ocean habitats such as reefs, as they eat species that feast on the corals. Some species are totally dependent on sharks for survival. The extinction of sharks would lead to the extinction of many other shark-dependent species, further reducing marine biodiversity​. An example is the pilot fish, who have a mutualistic relationship with sharks as they feed on parasites and food scraps.

The direct impact of global shark extinction on us would also be catastrophic. The oceans would become so degraded that the catch most of the world’s fisheries rely on would vanish or be disease-riddled and unsellable. Our oceans would become barren and empty, with some dominant populations outcompeting the rest. 

The mysterious case of great whites in South Africa

To help us understand the impact of what could happen if sharks start disappearing, we can look at stories where sharks have started to vanish. Along the coastline of Southern Africa, great white sharks were once the ocean’s number one predator. False Bay’s Seal Island was a famous shark spotting destination, where many visitors captured magnificent images of great whites breaching as they hunted and fed on the abundance of cape fur seals. Over the years scientists began to wonder why the number of great white sightings were dropping every year. Even more mysteriously, dead great whites began washing up on Cape Town’s beaches, completely disemboweled.

Two orcas, expertly skilled in removing the livers of great white sharks, were originally blamed for the dramatic decline and disappearance of great whites in False Bay and Gansbaai. These two male adult orcas have learned how to attack and kill great white sharks with deadly accuracy, which has meant the shark population has all but disappeared in the last 10 years. 

This kind of orca/shark behavior is a natural predation process, and has been observed in other parts of the world. Usually the great white populations return to an area within a few weeks or months. In South Africa, the great white sharks have still not returned.

In the years since, conservationists have challenged that orcas are fully to blame. Many attribute biodiversity loss and a lack of fishing regulations as key reasons for the great whites’ disappearance. Unchecked fishing in recent years has led to the collapse of the smooth-hound and soupfin shark populations, who are integral to the great whites’ food chain. Almost 90% of South Africa’s soupfin sharks have been fished out. Even if the practice was banned today it would take 50 years for the species to recover. This is one of the reasons, alongside the orcas, that has influenced the sharks’ relocation to other parts of the African coastline. 

The true impact of the disappearance of South Africa’s shark species is still unfolding, with big consequences on the economy, as well as local biodiversity. Great white sharks were once a big part of Cape Town’s $2.5 billion per-year tourism industry, and shark tours and cage diving bookings are down 50%. However, for biodiversity the problems are more of a concern. A 2019 study observed that sevengill sharks were seen at Seal Island—a top predator from a different habitat. 

Sevengill sharks are usually seen in the inshore kelp beds, and their behavioral shift away from the kelp could have community-level effects, as have been observed with other kelp-associated predator-prey dynamics (e.g. the sea otter–urchin–kelp trophic cascade witnessed off the Pacific Northwest of the United States). 

What can we do to protect the world’s sharks?

As we have observed from this one example alone, the disappearance of just one shark species can have a profound and long lasting impact on the ecosystem around it. So what needs to be done to protect the planet’s incredible shark populations?

• Combat Illegal, Unreported, and Unregulated (IUU) Fishing: Regulations like catch limits, quotas, restricting bycatch, and a total ban on finning are vital to shark protection. Unchecked and unregulated fishing is one of the biggest threats to shark populations today. 
• Create and expand Marine Protected Areas (MPAs): By creating shark sanctuaries and MPAs, sharks have a protected environment to breed and feed. Shark sanctuaries have been shown to be effective in protecting shark populations and allowing them to recover.
• Better law enforcement: Passing laws and regulations is one thing, but enforcing those laws is key to shark protection. Technology like satellite monitoring and drones can improve the surveillance of protected areas and ensure compliance with fishing regulations​.
• Strengthen international cooperation: Shark protection is a global responsibility, so it’s important nations collaborate on international agreements aimed at reducing IUU fishing and protecting shark populations, such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)​.
• Increased public awareness: Better awareness of the important role sharks play in marine ecosystems helps reduce demand for shark products and garner support for conservation measures​. Ecotourism can also offer a sustainable alternative to fishing for coastal communities.

Sharks are an integral part of marine ecosystems, and guaranteeing their protection and survival is important to our own. In some parts of the world, conservationists are going to great lengths to save sharks from becoming even more endangered. In Malta, one man came up with a sci-fi technique to save baby sharks from certain death. Watch Mission 17 below, and consider becoming a Planet Wild member to fund groundbreaking projects just like these!

About Planet Wild

Planet Wild is committed to rewilding the planet through monthly missions that work directly with grassroots organizations dedicated to fighting the biodiversity crisis. When you become a Planet Wild member, your contribution will directly fund innovative and exciting projects all over the world, so you can make a difference from home. Learn more about what we do here.

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*Glossary of terms

‍Cetaceans: Aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises.

‍Chondrichthyans: A class of jawed fish that contains cartilaginous fish which all have skeletons primarily composed of cartilage. Includes all species of sharks and stingrays. 

Driftnet fishing: A fishing technique where nets, called drift nets, hang vertically in the water column without being anchored to the bottom.

Fish Aggregating Devices (FADs): Man-made, usually floating wooden structures with hanging nets to attract fish. They can be floating or anchored to the seabed.

Pelagic fish: Fish that inhabit the water column (not near the bottom or the shore) of coasts, open oceans, and lakes.

Purse seine nets: An enormous wall of netting deployed around an entire area or school of fish.

‍Trophic cascade: An ecological phenomenon triggered by the addition or removal of top predators, impacting the predator and prey relationships throughout a food chain. Trophic cascades often result in dramatic changes in ecosystem structure.