Oysters Are ‘Nature’s Architects’—and Coastal Conservation’s Secret Weapon
To give new life to shoreline habitats, a growing number of projects are harnessing the reef-building power of oysters.
The twin islands of Alafia Bank were washing away. The state-designated bird sanctuary, whose sandy shores sit just above sea level in Florida’s Tampa Bay, offers a haven for more than 10,000 nesting pairs consisting of 17 different bird species, including Roseate Spoonbills and Reddish Egrets. But every year, some of the islets’ mangrove trees would topple as boat wakes, storms, and rising seas eroded the coast. In the 1980s, conservationists strapped thousands of donated tires together and placed them along the beach to stop waves from eating away at the shore, says Jeff Liechty, sanctuary manager with Audubon Florida. But the rubber barriers later broke apart.
So, in 2011, Audubon Florida, which leases and co-manages the site with The Mosaic Company and Port Tampa Bay, tried a different approach: lining more than a mile of shore with hollow concrete structures. The devices, which have holes to let water and sea life through, are designed to dampen wave impacts and attract some hardworking coastal residents—oysters. Within a year, mollusks covered the concrete, turning the breakwater into “a big buffet” for birds, Liechty says.
About 80 percent of the world’s oyster reefs have now been lost, leaving coastal habitats vulnerable.
It’s just one of a growing number of projects harnessing the power of oysters to restore coastal ecosystems. Given the right material, oysters build complex reefs. These natural formations, once abundant along North American coasts, began to disappear toward the end of the 1900s due to development, dredging, and overharvesting. About 80 percent of the world’s oyster reefs have now been lost, leaving coastal habitats vulnerable to erosion and climate change.
Today, recreating these natural barriers has become a popular alternative to other human-built breakwaters like concrete seawalls, which can do ecological damage and have failed to keep up with sea level rise and more extreme storms. NOAA has funded dozens of such “living shorelines” across the country and aims to wrap up the world’s largest oyster reef restoration in the Chesapeake Bay this year. “Oysters are nature’s architects,” says Bethany Carl Kraft, Audubon’s senior director for coastal and marine resilience. “In the last couple of decades in particular, we’ve seen this resurgence of interest in not just protecting our shorelines from erosion, but also using the benefits of nature to do that work.”
To rebuild reefs, engineers use various bases where baby oysters, called spat, can grow. In many waterways, these larvae naturally drift around and just need some solid material, usually other oyster shells, to start their next life stage. The concrete shapes at Alafia Bank feature ridges and divots that encourage spat to settle. In North Carolina’s Cape Fear River, conservationists offered both hollow concrete “reef balls” and mesh bags filled with recycled oyster shells. Meanwhile, on New York’s Staten Island, the state-led Living Breakwaters project used computer models to design a specific reef shape to blunt the area’s unique wave patterns; a local nonprofit is now placing live oysters on the stone-and-concrete structures. “There’s no one right way to do this. It’s an evolving science,” says Pippa Brashear, a resilience expert at SCAPE Landscape Architecture who worked on the New York reef.
Once infrastructure is installed, the benefits quickly start flowing in. The Cape Fear River reefs helped expand nesting habitat for species such as American Oystercatchers, which nest on piles of old shells, says Audubon North Carolina coastal biologist Lindsay Addison. Oysters also filter excess sediment and nutrients from the water, providing a healthier environment for fish. But the biggest benefit of the reefs is their ability to stop coastal erosion, Carl Kraft says. A 2011 study in Alabama found that adding natural breakwater reefs reduced erosion by 40 percent.
In Tampa Bay, recent severe weather put living shorelines to the test. Back-to-back hurricanes hit the area in late 2024, while Liechty was overseeing the construction of new oyster reef breakwaters around four more Audubon-managed sanctuaries. Once the storms passed, the results were clear: Along stretches of coast without the structures, wind and waves washed sand away. But on shores where new reef balls were already installed, mangroves still stood tall—a signal of resilience for birds’ beachfront homes.
This story originally ran in the Summer 2025 issue as “Shored Up.” To receive our print magazine, become a member by making a donation today.