Louisiana used 13 million pounds of discarded oyster shells to build 8,000 feet of living shoreline; studies found oyster reefs can reduce wave heights under some conditions

Oyster shells are post-meal waste for most Americans, left behind on the plates, swept into the bin, and gone. However, they might be the start of something completely different along the coast of Louisiana. National Geographic's 2003 report on the oyster-reef restoration in Louisiana notes that volunteers and community groups placed nearly 13 million pounds of discarded oyster shells to create over 8,000 feet of “living shoreline,” which is like using oyster shells as a physical barrier against an increasingly vulnerable coastline. The concept is simple: leave the shell in place, for the oysters to grow on it and for the reef it creates to act as a countermeasure to erosion.

It's a real issue in Louisiana, where the loss of coastal land isn't just a climate abstract. The question that becomes increasingly significant for the low-lying communities in the state, as they confront erosion, storms, and rising water, is: what will be left between homes, wetlands, and the Gulf? Oyster reefs themselves do not make up a magic wall, but research indicates that they could be a valuable component of that wall.

Your oyster dinner can have a second life


The rationale of the project is quite circular. After the restaurant oysters are eaten, the shells do not end up in landfills, but rather get collected; volunteers then use these shells for reef restoration, and the shells serve as a hard surface upon which young oysters can settle. In a 2005 study titled “The Potential for Created Oyster Shell Reefs as a Sustainable Shoreline Protection Strategy in Louisiana,” published in Restoration Ecology, researchers looked in detail at three-dimensional oyster-shell reefs in the eroding marshes of Louisiana as a shoreline protection measure.

Piazza, Banks and La Peyre’s study also contributed to developing the science behind making restored oyster reefs more than habitat projects. The other, more subtle benefit is that the reef is a living organism. The oysters may form a rough, complex structure that interacts with incoming water, as the oysters grow on the shells.

The perennial beauty of nature can serve as infrastructure, except when it doesn't

The key word in the sentence is can. Morris et al. in their 2021 research paper, “Large-scale variation in wave attenuation of oyster reef living shorelines and the influence of inundation duration,” published in the journal Ecological Applications, demonstrated that oyster-reef living shorelines can decrease wave height but that effectiveness is highly dependent on the frequency of inundation. Structures inundated less than half the time reduced wave height up to 68%, while reefs more appropriate for oyster establishment (inundated more than half the time) reduced wave height closer to 5% than reefs without structures. Just because a seawall is natural, that does not necessarily make it a better seawall. The design, elevation, location, and local water conditions count.

Louisiana’s experiment is bigger than oysters

The 8,000-foot Louisiana project is noteworthy because it takes a community approach to coastal restoration as opposed to a one-engineering-fix solution. Through the work of volunteers and communities, the Coalition to Restore Coastal Louisiana has transformed restaurant shells into reefs and living shorelines, including sites that will help preserve culturally significant places along the coast, according to the reporting by National Geographic.

The concept is slowly moving past the individual projects. According to Restore America’s Estuaries, NOAA-backed oyster-shell recycling and reef restoration are spreading across the Gulf states, and this one-of-a-kind initiative is known as the Gulf Regional Oyster Network. Its goal is expanding development, sharing oyster-reef restoration technology, and involving communities.

The solution

Louisiana's oyster reefs could be a feel-good climate story: "eat oysters, save the coast.” But it's not quite as neat in real life. The research points to only specific environmental conditions in which oyster reefs are most effective, and to the fact that oyster reefs cannot provide all types of coastal protection. Morris et al. found that living shorelines can be a challenge to design to maximize both the oyster habitat and wave-attenuation benefits; thus, restoration is flexible and adaptable to a particular shoreline. Nonetheless, the concept of the principle is strong. Empty shells create habitat. Habitat becomes reef. The reef can act as a barrier. A common item on the American dinner table can be one small part of a broader coastal-restoration effort. This is a climate solution that has its limits, and acknowledging that, it leverages existing resources and brings nature back to serve humanity.