Sea walls have existed for thousands of years. They are built to prevent tides and waves from eroding our shoreline while protecting our communities from flooding. They are generally constructed of boulders, concrete, steel, vinyl, wood, and aluminum, fiberglass composite and biodegradable sand bags. They are expensive and require maintenance and replacement. They are at the mercy of rising sea levels and extreme events that can’t be predicted like Hurricane Sandy, where the waves come in over their top.
A team of researchers from the University of North Carolina at Chapel Hill published a study last April in Nature Climate Change suggesting rehabilitated oyster reefs could be used to provide our coastline from erosion and sea level rise.
Oyster reefs, also known as oyster bars, are submerged habitats. Some oyster larvae drift through the water and attach to an existing wall and continue growing. They join together forming an oyster reef. Once attached to a surface, oysters will stay there for the remainder of their lives. The reefs play an important ecological role by providing habitat for a number of species and improve water quality. They are also commercially valuable. Unfortunately, their numbers have been declining due to over harvesting and disease.
For their study, Antonio Rodriguez and his colleagues built 11 oyster reefs in intertidal areas on the North Carolina Coast and continued to measure them between l997 and 2011. They found that the reefs grew rapidly at a pace that would match any future sea level rise. Rodriguez said when the reef grows, “it’s a big cemented structure so it’s really hard, unlike the natural shoreline which is very soft. It will take the blunt of the waves and dampen them so that when they reach the shoreline, they have less of an invasive effect.”
An additional benefit is financial as an oyster reef bears a minimal financial burden in comparison to the construction of a sea wall. Rodriguez estimated that an entire reef would cost only a few hundred dollars.
The negatives to oyster reefs are that they have to be built close to the shoreline at the right depth and exposed to air 40% of the time. They also can be prone to diseases that can wipe out entire reefs. The research study reefs were built in intertidal reefs that are not found north of the Virginia coast, and if built further out to sea, they might not grow as quickly. Ocean acidification or predation could also hamper their growth.
More research is needed, but this may be the next big thing in managing our coastal waters.