In the last century, 85% of the world’s oyster reefs have vanished. And we’re only recently beginning to understand what that’s 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.
Now, several projects from New York to the Gulf of Mexico and Bangladesh are aiming to bring the oysters back. Because not only are oysters vital ecosystems; they can also protect us from the rising oceans by acting as breakwaters, deflecting waves before they hit the shore. It won’t stop the seas from rising – but embracing living shorelines could help protect us from what’s to come.
When you picture 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 not 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 be an effective defense against the rising ocean.
We’re losing our coasts to climate change. As oceans 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.
Oysters’ charisma lies in their functionality rather than their form. Oysters don’t move around. And that’s precisely part of the appeal. Oysters stick together. Baby oysters called “spat” attach to older and even dead oysters to grow. And over generations, all of these oysters reproducing, it builds up the oyster reef.
In some places, that sturdy reef can help defend the coast by dampening the force of incoming waves. 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 has reflected 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 limit the damage. And the larger they grow, the more protection they can offer.
As time goes on, sea levels will rise. Unlike artificial breakwaters that will need to be rebuilt over time, oyster reefs 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 grow.
In New York, one organization puts recycled shells in cages for oyster spat to grow on. Groups in Bangladesh and the US have placed considerable concrete barriers offshore for oyster spat to grow on. Now, on their own, concrete structures like this are effective breakwaters.
So, why add oysters? To understand, it helps to look at a more familiar type of reef. 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 bay’s bottom, and clean water is expelled.
A single oyster can filter up to 50 gallons of water every day. As the water clarity improves, seagrasses start to grow, fish return, and other sea creatures make the crevices in the reef their home. 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, we set up, more or less, walls, to try to slow the rate of waves, 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 the point. We don’t think we can put it back just the way it was. We don’t think that’s necessarily a realistic goal. But we’ve got an excellent opportunity to start thinking about multiple benefits and the different kinds of needs of society, whether to reduce wave impacts, offset nutrient inputs, or generally increase the bay’s health and resilience. 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. It feels hopeful. And it feels like something that we can achieve.