Oysters and Mangroves: How Far Can They Go?

North Carolina, one of the places hit hardest by Hurricane Matthew, had been battling coastal erosion long before the storm. The threat comes not only from the ocean side, but from the land as well. As this article explains, “ditching and draining for forestry and agriculture changed the inland hydrology and allowed salt water to penetrate miles inland, a dynamic exacerbated by intense hurricanes and sea-level rise. Salinization causes forests to turn to shrublands, shrublands to become marsh, and shoreline to erode into the sound—as much as 10 to 12 feet each year.”

The article predates Matthew, but it details combinations of techniques being used to prevent or reverse erosion in North Carolina, New York, and elsewhere—and shows how they might be used in other places. The techniques center on restoring ecosystems to enhance the natural processes that once protected the shorelines. They include planting salt-tolerant vegetation; restoring oyster reefs, which have water-quality benefits as well as providing a barrier against wave-induced erosion; rebuilding and reconnecting forested floodplains; and even replanting mangrove forests, which research has shown can help accumulate sediment and prevent inland encroachment of sea water.

Many of these demonstration projects are led and funded by the Nature Conservancy. The organization acknowledges that it’s a balancing act; on the one hand, it says, natural systems alone can’t protect coastal areas that are already heavily developed: “Natural defenses are not a panacea, but they are a valuable tool.” On the other, “Just building higher sea walls or more levees is equally unrealistic.” The article quotes the Conservancy’s director for North American conservation programs: “It’s not green versus gray [infrastructure]. It’s both/and.”