New report questions hard-edged 'living shorelines' in estuaries

Science Codex: The increasing use of large breakwaters and other hard structures to reduce erosion in "living shorelines" along coastal estuaries may be no better for the environment than the ecologically harmful bulkheads they were designed to replace, according to a report this week by scientists at Duke and Western Carolina universities.

Originally, living shorelines were designed to use natural methods such as replanted native marsh grasses and oyster reefs to stabilize and protect eroding shorelines.

Many environmental groups and government agencies have advocated this approach in recent years as an eco-friendly alternative to wooden bulkheads and other forms of shoreline armoring in low wave-energy environments such as estuaries and sounds.

But this new report reveals that since 2000 the use of large-scale hardened structures such as rock walls or offshore breakwaters has increased dramatically at a growing number of sites classified and funded as living shorelines. The researchers surveyed sites from Maryland to Texas -- including the Chesapeake Bay, North Carolina's Pamlico Sound and the South Carolina Low Country -- and found dozens of miles of living shorelines armored with hard stabilization, constructed at a cost of tens of millions of dollars.

"The intent is often to deflect waves and provide extra protection until new grasses or oyster reefs can take hold. But once installed, the barriers are rarely removed," said Orrin Pilkey, James B. Duke Professor Emeritus of Geology at Duke's Nicholas School of the Environment.

"Many projects now contain massive rock structures, with little habitat gain," he said. "These kinds of living shorelines are probably no more ecologically responsible than bulkheads."

"We're concerned the use of massive hard-engineered structures in some of these so-called living shorelines will cause long-term environmental degradation, provide a false sense of accomplishment and shift the focus away from trying to maintain the most natural estuarine shoreline feasible," said Robert S. Young, professor of geology and director of the Program for the Study of Developed Shorelines at Western Carolina....

Old sea defence on Dee estuary Wall of stones placed upright in a line - now overwhelmed by erosion, shot by Peter Aikman, Wikimedia Commons via Geograph UK, under the Creative Commons Attribution-Share Alike 2.0 Generic license