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The Environmental Cost of Shoreline Hardening

Wednesday, June 21st, 2017

New study shows hardened shorelines may mean fewer fish and crustaceans. 

by Ryan Greene

A split image with a wooden bulkhead on the left and a rocky riprap revetment on the right.

A new SERC study shows that both bulkheads (left) and riprap revetment (right) are associated with lower abundance of several species of fish and crustaceans in the Chesapeake Bay and the Delaware Coastal Bays. Credit: SERC

For decades, ecologists have suspected that hardened shorelines may impact the abundance fish, crabs, and other aquatic life. But now they have evidence that local effects of shoreline hardening add up to affect entire ecosystems. A new study by scientists at the Smithsonian Environmental Research Center (SERC) shows that more shoreline hardening means fewer fish and crustaceans in our waters.

Given the predictions for the coming years (i.e. rising seas and more of us living on the coast), this finding is a cause for concern. Many people will likely try to protect their land from flooding and erosion by armoring their shorelines with vertical retaining walls (bulkheads) or large rocks (riprap revetment). But as SERC researchers found in their new paper, published in Estuaries and Coasts, the impact of these hardened shorelines adds up.

Lead author and former SERC postdoc Matt Kornis likens shoreline hardening to littering. While each individual bit of trash isn’t a huge problem, the combined effect can be enormous. Kornis, now a biologist for the U.S. Fish & Wildlife Service, says the same is true of shoreline hardening. Each individual bulkhead or riprap revetment may not be catastrophic, but cumulatively they can contribute to shrunken populations of ecologically—and economically—important species like the blue crab.

“Shoreline hardening can cause loss of habitats important for young fish, like wetlands and submerged vegetation,” Kornis says. “That may be one reason we observed low abundance of many species in estuaries with a high proportion of hardened shoreline.” Click to continue »