7 Reasons Why We're Lucky to Have Sharks

Sharks are widely respected by people, but that doesn't always mean their presence is appreciated. We tend to focus on the small chance of being bitten, overlooking the valuable benefits these ancient fish have to offer.

Of more than 375 known shark species, only about 30 are known to have attacked a human, and even these species pose little risk overall. Millions of people enter the ocean every year, yet the global yearly average for unprovoked shark attacks is 75, fewer than 10 of which are fatal. The odds of a shark attack are roughly 1 in 11 million, much lower than other beach hazards like rip currents, lightning or boats.

Sharks, on the other hand, have very good reasons to fear us. Humans kill an estimated 100 million sharks every year, largely due to fishing, finning and accidental bycatch. Combined with less direct threats like climate change and overfishing of prey species, this is raising serious concerns about the future of some shark species.

And the decline of sharks is not just an academic or ethical issue. Sharks play important roles in ocean ecosystems, and have also become a useful source of biomimicry. If sharks' recent troubles don't improve soon, we could end up learning to appreciate their presence the hard way. In hopes of shedding more light on the bright side of sharks, here are a few ways they benefit people:

Sharks help regulate marine food webs.

Over the past 400 million years or so, sharks have evolved deep, interdependent relationships with their ecosystems. These systems consist of complex food webs, often with sharks at the top as apex predators. Like tigers, wolves and other top-level predators, many sharks are keystone species, which means they play such key roles that their disappearance would significantly alter the ecosystem.

Along the U.S. Atlantic Coast, for example, overfishing between 1970 and 2005 led to the collapse of several large shark populations — scalloped hammerhead and tiger sharks may have declined by more than 97 percent, while smooth hammerhead, bull and dusky sharks fell by more than 99 percent. This led to an explosion of prey species once suppressed by those predators, including hordes of cow-nosed rays that wiped out North Carolina's bay scallop fishery, researchers found.

Studies have revealed similar dynamics elsewhere, too. Off the coast of Brazil, a 2014 study found that tiger sharks, dusky sharks, sand tiger sharks, scalloped hammerheads and smooth hammerheads "are species with large ecological function values and may exert a powerful influence over lower levels" of the food web. And in Australia, a 2013 study found that as shark numbers shrank, mid-sized predators like snapper increased while smaller, algae-eating fish faded.

Sharks protect coral reefs and seagrass beds.

As they've evolved along with their ecosystems over time, many sharks have grown so influential their mere presence seems to protect the habitat. In the 2013 study mentioned above, the loss of big, predatory sharks at coral reefs off northwestern Australia correlated with a rise of "mesopredators" like snapper and a decline of small herbivorous fish. With fewer grazers around, algae can overwhelm a reef system and limit its ability to rebound from stress like bleaching.

Sharks have been shown to protect other kinds of ocean ecosystems, too, in some cases by hunting herbivores instead of helping them. That's the case in Western Australia's Shark Bay, where a long-term study of tiger sharks has found benefits similar to those of apex predators on land. When seagrass beds were struggling after a 2011 heat wave, they recovered more quickly in areas where tiger sharks roamed, since the sharks scared away grass-eating sea turtles and dugongs. The sharks don't even need to kill to have this effect; fear alone can change how herbivores forage.

"It's all about how predators and prey interact," Florida International University (FIU) scientist Mike Heithaus said in a statement. "Just the fear of sharks can be enough, in many cases, to keep a marine ecosystem healthy and able to respond to stresses."

Some sharks help mitigate climate change.

Tiger sharks' protection of seagrass may ripple far beyond the beds themselves. While seagrass beds occupy less than 0.2 percent of the planet's oceans, they account for more than 10 percent of all carbon absorbed annually by ocean water. Per unit area, these underwater meadows can store up to twice as much carbon as Earth's temperate and tropical forests, according to FIU seagrass expert James Fourqurean.

Coastal seagrass beds hold up to 83,000 metric tons of carbon per square kilometer, mostly in the soils beneath them. A typical forest on land, by comparison, can store about 30,000 metric tons per square kilometer, mostly in the trees' wood. Losing these meadows not only disrupts the local ecosystems where they grew, but also removes a valuable buffer against global greenhouse gas pollution. By protecting seagrass, sharks are thus indirectly helping fight human-induced climate change.

Sharks are worth more alive than dead.

Although large numbers of sharks are hooked or netted accidentally as bycatch, humans also widely hunt them for their meat and their fins, a key ingredient in the Chinese delicacy shark-fin soup. It's rarely a good idea to eat shark meat or cartilage, however, since the predators are especially prone to bioaccumulation of heavy metals like mercury. And despite the purported health effects of shark fins, which are relatively flavorless, there's no evidence to suggest they confer any benefits.

Shark fins can fetch notoriously high prices, yet that one-time payoff for a bland chunk of cartilage still pales in comparison with the value a live shark can generate during its lifetime. Aside from the economic effects of their ecological roles, certain shark species are tourist magnets, and as long as they're part of a responsible eco-tourism industry, they can provide a major boost for local economies.

Australia, for instance, has four major shark-tourism industries — great white, gray nurse, reef and whale sharks — worth a combined $25.5 million per year, according to a 2017 study. At South Ari Atoll in the Maldives, whale-shark tours brought in $7.6 million in 2012 and $9.4 million in 2013. Reef-shark tourism adds roughly $18 million per year to the economy of Palau, a 2011 study found, which is 8 percent of the country's gross domestic product. Each of about 100 sharks in Palau's top dive spots is thus worth $179,000 a year, totaling $1.9 million over its lifetime. If each shark's meat and fins would sell for $108, as the researchers estimated, that means tourism appeal alone can make some sharks 17,000 times more valuable alive than dead.

Sharks are inspiring better airplanes and wind turbines.

Although sharks are still killed for their meat and fins, there's also a growing push to steal concepts and designs from wildlife instead of just taking the wildlife itself. That includes things like imitation shark-fin soup, but also far more advanced ideas that can improve a wide array of technology. Known as biomimicry, this has rapidly gained popularity in recent years, drawing inspiration from all kinds of creatures.

With sharks, the focus of biomimicry is mainly on V-shaped, tooth-like scales known as denticles. Scientists have been studying these scales for decades, and as Harvard University researchers reported in 2018, denticles offer powerful aerodynamic qualities by both reducing drag and increasing lift. Many kinds of vehicles use vortex generators to improve their performance, but scales modeled after shark skin seem to provide higher-powered vortex generation with a lower profile.

Shark-inspired vortex generators can achieve lift-to-drag ratio improvements of up to 323 percent compared with an airfoil lacking vortex generators, the study's authors reported, indicating they can outperform traditional designs. "You can imagine these vortex generators being used on wind turbines or drones to increase the efficiency of the blades," study co-author Katia Bertoldi said in a statement. "The results open new avenues for improved, bioinspired aerodynamic designs."

Sharks could help us battle superbugs.

Shark denticles also give the fish other superpowers beyond aerodynamics, such as resistance to algae, barnacles and other pests that colonize the skin of marine animals. Shark skin itself is not an antimicrobial surface, but it is highly adapted to resist attachment by these kinds of organisms, and that resistance has inspired some powerfully antimicrobial synthetic materials. That includes the micropattern known as Sharklet, an array of tiny ridges modeled after shark skin.

In a 2014 study, Sharklet harbored 94 percent less MRSA bacteria — short for Methicillin-resistant Staphylococcus aureus, a dangerous drug-resistant superbug — than a smooth surface, and also outperformed copper, a common antimicrobial material that's toxic to bacterial cells. Rather than relying on toxins or antibiotics, Sharklet's antibacterial properties are entirely structural, modeled after the way shark denticles naturally repel algae and barnacles.

The U.S. already has more than 2 million bacterial infections per year, leading to about 23,000 deaths, and the rise of drug-resistant strains like MRSA — fueled by overuse of antibiotics — poses a growing public-health threat. Shark-inspired micropatterns can reduce this risk, especially when fortified with other antibacterial substances like titanium dioxide nanoparticles, which boosted the material's resistance to E. coli and Staph infections in a 2018 study.

Sharks are just inherently cool, even if they don't help us.

Sharks have existed on Earth for almost 450 million years, which means they were prowling the oceans 200 million years before the first dinosaurs existed. For all the reverence we give dinosaurs and their extinct ilk, it's worth noting that even older animals have been swimming under our noses this whole time. These animals may indirectly benefit us in the ways described above, but even if they didn't, they're innately amazing creatures that deserve to exist for their own sake.

Sharks have racked up a lot of incredible quirks over that time, too many to list here. They've diversified into everything from the enormous whale shark, the largest fish on Earth, to the tiny dwarf lanternshark, a deep-dwelling species that can fit into a human hand. There are cookiecutter sharks that take little chunks of flesh from living prey, goblin sharks with protrusible jaws and giant filter-feeders that gulp down plankton. Greenland sharks can live for 400 years, not reaching sexual maturity until their 150th birthday, boasting the longest known life span of any vertebrate animal. Many sharks have a legendary sense of smell, along with special organs to sense the electrical fields of prey, and hammerheads enjoy 360-degree vision.

Certain species can pose a threat to people, of course, but that relatively small risk shouldn't blind us to all the benefits and fascination sharks can provide. And even though clashes are rare, once you know how to avoid a shark attack, it can be much easier to focus on how lucky we are to share the seas with these phenomenal fish.