Shoring up nature’s resistance

Carter Smith, lecturing fellow in the Division of Marine Science and Conservation, heads the Living Shorelines team and has been working with Silliman on Duke Restore since its inception in 2019. The Duke Marine Lab on Pivers Island, in Beaufort, N.C. itself exhibits a living shoreline. For the past few years, the team has been working with the U.S. Navy on a shoreline project at the Marine Corps Air Station in Cherry Point, N.C. that will be installed soon.

“Living shoreline” is a broad term that covers a range of interventions. “On the really green end of the spectrum, you could just restore a salt marsh. In a low-energy area, that’s going to help attenuate sediments, and help provide coastal protection. In that sense, it might mimic a natural salt marsh really well. On the opposite end of the spectrum, you could have a very highly engineered shoreline, this is closer to the project that we’re working on at Cherry Point, where coastal protection is really important,” said Smith. “They’re trying to protect the shoreline from major hurricane events so they’re putting in a very highly engineered large, granite breakwater, with some marsh plantings behind it.”

Smith described adaptations like putting in a granite sill just offshore a marsh, with gaps that allow fish passage, so that the fish aren’t obstructed from using the marsh behind these breakwaters, and can flux in and out at will, at high tide. In Beaufort, local species like red drum, pinfish and mummichog swim through to protected areas.

“People are excited if they hear that there are blue crabs and red drum in an area,” Smith said. Red drum, or channel bass, is the state saltwater fish of North Carolina. 

Near conventional infrastructure, hardened shorelines like concrete seawalls, she said, scientists observe significantly lower biodiversity across plant and animal groups. “What we know now is that they’re not actually as effective, in a lot of circumstances, as people think that they are and they’re definitely not as resilient in the long term, because they typically have very high maintenance costs. They require a lot of continued human intervention.”

Seawalls are built with a fixed sea level in mind, “which is really problematic, if we’re going to see feet of sea-level rise, in North Carolina, over the next 50-75 years,” Smith said. “That makes a big difference in terms of the effectiveness of this structure that was built assuming that the sea level was fixed.” 

Using natural elements in coastal infrastructure, she said, has multiple benefits. “One, it is going to be better for the environment — hopefully, we’re going to see higher biodiversity along these natural shorelines if we do it correctly and restore significant portions of habitats — and two, it actually has potential to be really effective, because natural ecosystems can adapt! And change. And they can repair if they get damaged,” she said. “And so, there’s the potential for them to be a more sustainable and more resilient option.”