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What Would An Ocean Without Sharks Look Like?

Imagine taking the lion out of the plains or the eagle out of the air. Consider how food webs, strung together by millions of years of survival and predation, would stretch and strain if we did. We know that when we take an apex predator out of an ecosystem, other organisms fill the gap with sometimes disastrous consequences. But that is exactly what we are doing with the sharks in our oceans.

In his latest video, biologist Joe Hanson tries to get beyond the fear and fable surrounding these sleek predators and to the heart of the problem: In a world where we kill 100 million sharks every year (over 3 per second, as Hanson tallies), what would an ocean without sharks look like? In short, not good:

The importance of sharks is directly related to their prowess as predators. Toothy eating machines they might be, but sharks keep other, peskier fish in check. Sharks are one of the equilibrium keepers of the state of the ocean as we know it. In fact, we already know how important apex predators are to their ecosystems because of how we’ve treated whales and wolves.

Writing at io9, science writer Jason Goldman notes that when wolves were hunted out of Yellowstone, the effect was swift:

When wolves were driven out of Yellowstone, the elk population exploded because they were no longer supressed by wolf depredation. But more elk meant that the plants they ate suffered. And the bears, beavers, and bison, who relied on many of the same plants as the elk, suddenly found themselves without enough food to eat. The entire Yellowstone ecosystem had shifted.

After the Yellowstone wolves were reintroduced, the equilibrium of the forest returned. Large predators’ “ecosystem services” are often overlooked, Goldman notes.

In the same piece, Goldman shows just how important large predators are by linking whales to climate change. The amount of carbon alone that blue whales and their kin are able to gobble up in the form of krill and plankton could be equivalent to some of our planned carbon sequestration efforts, if the whales returned to their pre-whaling levels.

Being at the top of the food chain precisely means that you are an essential link in that chain. If that link is suddenly broken, if the chain changes faster than nature has ever experienced, there will be a radical shift. If we continue removing sharks from our oceans, that shift will likely have unintended consequences. Jaws is scary, but a future without any sharks is scarier.

Kyle Hill is the Chief Science Officer of the Nerdist enterprise. Follow the continued geekery on Twitter @Sci_Phile.

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