Seawalls protect our coastlines and have environmental impact

Many of America’s coastlines are dotted with massive armored structures of the non-military variety: seawalls. These man-made obstructions are designed to protect the shoreline and any human lives and infrastructure that may dwell behind it – particularly in urban areas.

But not every seawall is the same. These structures vary greatly depending on environmental setting, ranging from huge seawalls and revetments along the open coast to small bulkheads and manmade oyster reefs located in estuaries and tidal marshes. And although the design of these walls varies widely, the research hasn’t. While research efforts regarding the ecological effects of seawalls have increased, they have generally focused on specific settings and have not provided a bigger picture of how seawalls influence their environment.

A recent study by marine scientists at UC Santa Barbara and their colleagues from three coastal sites in the National Science Foundation’s Long-Term Ecological Research (LTER) network looks to increase knowledge of seawalls’ ecological impact. Their study attempts to generalize the ecological responses to armoring throughout a range of coastal settings where the structures exist.

“The size and shape of these manmade structures often result in the loss of intertidal habitats,” explains lead author Jenifer Dugan, a research biologist at UCSB’s Marine Science Institute. “The extent of that loss is a function of environmental setting, structure type and how far seaward and along the shore the structure extends.”

The three unique LTER programs analyzed armoring at a variety of different sites. At the Santa Barbara Coastal LTER, they studied the impact of seawalls on open coast beaches – revealing a significant ecological impact on many species, including birds. The Georgia Coastal Ecosystems project focused on the effects of small-scale armoring in salt marshes, while the Virginia Coast Reserve LTER looked at man-made oyster reefs and living shorelines being used as coastal protection structures.

“What was novel about this cross-site collaboration was putting these site-specific studies into perspective by making comparisons across a broad range of habitats,” says study co-author Merryl Alber, a professor at the University of Georgia.

The researchers also designed a model in order to analyze the environmental location relate to hydrodynamic energy, such as wave and tide action. Using existing literature, they evaluated how accurately their model could predict the ecological impact of seawalls.

Their review of previous studies showed how unbalanced previous research was in regards to varying environments and key factors of ecological effects.

“Our review not only revealed major gaps in knowledge but also highlighted the fact that existing information on ecological responses to armoring is unevenly distributed across soft sediment habitat types and does not necessarily cover the range of potential environmental and armoring contexts,” says co-author Kyle Emery, a doctorate candidate at UCSB. “Our work makes it clear that there is certainly room for more studies.”

The research team believes that coastal armoring structures will likely face greater hydrodynamic energy as sea levels continue to rise, resulting in even more significant ecological impacts on many environments.

With these increased research efforts and an effective model to determine the ecological effects of shoreline armoring, scientists are enhancing our knowledge of how these practices affect the world around us.

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By Connor Ertz, Earth.com Staff Writer