Marine scientists evaluate coastal armoring

Overlapping constituencies and interests strive to preserve an appreciation for beauty and "nature" but perhaps without the accompanying respect for how nature actually works. This new NSF-supported study highlights that there is just so much that we don't understand about how the world works:

For nearly a century, the O'Shaughnessy seawall has held back the sand and seas of San Francisco's Ocean Beach. At work even longer: the Galveston seawall, built after America's deadliest hurricane killed thousands in Texas in 1900.

These are just two examples of how America's coasts -- especially those with large urban populations -- have been armored with human-made structures.

Though these structures help protect communities against natural disasters, these "lines in the sand" limit the ability of the shoreline to respond to changes in sea level and other coastal processes.

Recent research on the resulting ecological effects has largely been conducted in specific settings, making it difficult to generalize the results across ecosystems and structure types.

Now a study by marine scientists affiliated with three coastal sites in the National Science Foundation's (NSF) Long-Term Ecological Research (LTER) network provides a key first step toward generalizing ecological responses to armoring in the widely diverse coastal settings where these structures are used.

The team's findings appear online this week in a paper in Estuaries and Coasts, and will be published this fall in a special issue of the journal.

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Researchers at the Georgia Coastal Ecosystems LTER site have conducted studies of small-scale armoring in salt marshes. And investigations at the Virginia Coast Reserve LTER site have focused on the use of oyster reefs and living shorelines as coastal protection strategies.

"What's new about this cross-site collaboration is putting these site-specific studies into perspective by making comparisons across a broad range of habitats," said paper co-author Merryl Alber, a marine scientist at the University of Georgia and principal investigator of the Georgia Coastal Ecosystems LTER site.

The vulnerability and beauty of the Georgia coast go hand-in-hand. The barrier islands themselves have been poorly utilized since the plantation era, and their function not much better understood in the time since. The effects of rising seas will reek havoc upon many areas, but in some ways this will provide a forced, long-term perspective on coastal areas - whatever the causes of the rising tides. Kudos to Alber and her colleagues on this important work, and let's hope it begins to inform our relationship to these amazing coastal ecosystems.

Image: south end of Tybee Island, showing the sharp vertical drop between the beach and dunes because of the seawall between them. (Photograph by Anthony Martin)