Sea walls have been around for centuries. They protect prized coastal property—San Francisco's Embarcadero, Taylor Swift's Rhode Island mansion, and the Indian shores of Pondicherry, to name a few—by deflecting incoming waves and storm surges.
The town of Bay Head, New Jersey, credits a hidden, hundred-year-old sea wall with saving scores of houses from destruction during Hurricane Sandy. In a place where homes could have been reduced to rubble, only "minor structural effects" were observed, scientists say: "Despite the immense magnitude and duration of the storm, a relatively small coastal obstacle—the seawall—reduced potential wave loads by a factor of two."
More and more cities are expected to suffer from extreme weather in the years ahead—and more frequently. Worldwide sea levels are expected to rise, too, putting coastal communities at great risk. Accordingly, the global market for sea walls is projected to be worth $9 billion by 2023.
The problem is that demand is growing for what one market-research firm calls "next-generation" sea walls, built with more advanced, pricier materials. Seattle, for example, is spending more than $300 million to reconstruct an existing sea wall on Elliott Bay. But not all cities can afford this kind of project, and as the sea-wall market grows, construction costs may continue going up.
In these cases, there may be a less high-tech solution: oyster reefs. They're not as formidable-seeming as the concrete- and granite-based boulders installed on beaches and under boardwalks around the country, but they have other attractive advantages.
Antonio Rodriguez, a coastal geology professor at the University of North Carolina at Chapel Hill, and his colleagues spent 15 years measuring oyster reefs in intertidal zones on the Carolinian coast. In a study released this week, the team reports that, over the years, these reefs have grown at a pace that would match any future sea-level rise. According to Rodriguez, this is a good case for actively restoring oyster reefs on the East Coast. "One could end up with a reef that will help protect the shoreline from erosion, filter water, provide fish habitat, and be able to keep up with sea-level rise," he says. "No rock sill can do those things."
Oyster walls are dynamic, in other words. Conventional sea walls, tough though they may be, are static. After the ocean rises enough, waves will be able to swoosh over the top of stone walls. Oyster reefs grow by accumulating drifting oyster larvae that latch on and are kept in place by sediment buildup. In addition to protecting land from sea, the oysters also filter water—plus, they can be commercially harvested for food.
It's an eco-friendly solution, for sure, but restoring oyster habitat isn't the easiest or cheapest thing to do. New York architect and Columbia University professor Kate Orff floated this idea years ago, coining the term "oyster-tecture" in a lauded TED talk. Since then, Orff's concept has popped up regularly in publications like The Atlantic Cities and Bloomberg, but specific project proposals haven't progressed much.
If oyster-tecture ever does happen—and Rodriguez's research may help it along—it will be a great example of American adaptation to climate change.
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