How Oysters Can Stop a Flood?

In the last century, 85 percent of the world’s oyster reefs have vanished. And we’re only recently beginning to understand what that cost us. While they don’t look incredibly appealing from the shore, oysters are vital to bays and waterways around the world. A single oyster can filter up to 50 gallons of water every day. And over time, oysters form incredible reef structures that double as habitats for various species of fish, crabs, and other animals. In their absence, our coastlines have suffered.

 For example, in New York City, there are so many iconic things that come to mind. But, before the yellow cabs and hot dog stands, New York was known for something else; Oysters.  From the 1600s through the 1800s, New York was booming with them. And it was oysters, not hotdogs, sold streetside by the millions. Oyster reefs covered over 220,000 acres along the coastline. The reefs were so large that ships needed to navigate around them. But, of course, this isn't the case today. Oysters were overharvested nearly out of existence, and just in New York. Experts estimate we've lost 85% of the world's oyster reefs in the last 200 years. Today we’re trying to put them back. Because this animal that you often find on a dinner plate might actually be an effective defense against the rising ocean. We are losing our coasts to climate change. As ocean levels rise, the water erodes the shoreline. This pushes the entire coast back, encroaching on homes and destabilizing land. So, enter the oyster.  This uncharismatic rock of an animal.

 ȘTEPHANIE WESTBY: “Oh come on! You don't think they're charismatic?”

Stephanie Westby has been helping to restore oyster reefs in the US's Chesapeake Bay for over 10 years. Westby: Their charisma really lies in their functionality, rather than their form. Oysters obviously don't move around. And that's exactly part of the appeal. Oysters stick together. Baby oysters called "spat" attach to older and even dead oysters in order to grow. Westby: And over generations, all of these oysters reproduce, it builds up the oyster reefs. In some places, that sturdy reef can help defend the coast by dampening the force of incoming waves.

 Westby: “If you have an oyster reef that's "intertidal" -- that sticks up at low tide then it can perform some of that wave energy protection function. Oyster reefs can break up waves by catching the brunt of the force. Part of the wave is deflected back to the ocean, and the rest can more gently reach the shoreline, which slows long-term erosion. On its own, an oyster reef won't stop a hurricane-level storm surge, but it could definitely limit the damage. And the larger they grow, the more protection they can offer: As time goes on, sea levels will rise. Unlike man-made breakwaters, that will need to be rebuilt over time, oyster reefs just keep growing upward. Various organizations around the world are working to restore oyster reefs. But reef restoration isn't as simple as just dumping oysters into a bay. They need something to stick to in order to grow. In New York, one organization puts recycled shells in cages for oyster spat to grow on, and groups in Bangladesh, and around the US, have placed large concrete barriers offshore for oyster spat to grow on. Now, on their own, concrete structures like this are actually effective breakwaters.

 So. Why add oysters? To understand, it helps to look at a more familiar type of reef: Seab Corson: “Oyster reefs provide much the same function as coral reefs. They provide the same kind of habitat. They are the underpinning of the ecological systems where they exist, just like coral reefs. Oysters are filtration systems. They eat by pulling in large quantities of water. Algae, nitrogen, and other contaminants are eaten, or harmlessly dumped to the bottom of the bay, and clean water is expelled.” A single oyster can filter up to 50 gallons of water every day. As the water clarity improves, sea grasses start to grow, fish return, and other sea creatures make the crevices in the reef their home. Seab Corson: “They are this aggregating, reef-building, hard structure. And so, if you look at the way we try to deal with reducing erosion right now, as a society, for the most part, we put rocks, big pieces of concrete, for the most part, we put rocks, big pieces of concrete, reduce the wind-driven erosion, that type of thing. Oysters can serve in that capacity in many ways, but bring added advantages. Places like New York city or even the Chesapeake Bay are way too industrialized to bring back the reefs of the 1600s. But that's not really the point. Corson: “I don't think we can put it back just the way it was. I don't think that's necessarily a realistic goal. But I think we've got a great opportunity when we start thinking about multiple benefits, and the different kinds of needs of society, whether it's to reduce wave impacts, or offset nutrient inputs,  or generally increasing the health and resilience of the bay. Resiliency against the rising oceans isn't as simple as undoing the mistakes we made in the past. We don't live the way we did 200 years ago, and the world looks very different. But what we can learn from oysters, is that restoring one species from the past can create a chain reaction to a more sustainable future.” Corson: “It feels hopeful. And it feels like something that we can achieve.”