Ecology, Climate Change and Related News

Conservation Science for a Healthy Planet

Eroding coasts need protection — and new solutions are at hand

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by Maria Dolan March 2018  Read full ensia article here

Graphic courtesy of NOAA

…shorelines with seawalls, rip-rap (jumbled boulders) or other forms [are] what’s often called shoreline armoring. A 2016 paper describes detailed research …that shows how Puget Sound armoring can change everything from the texture of the beach (beaches get coarser, with less sand and more cobble) to the presence of logs and washed up plant life. The more armoring along a stretch of beach, the more impact it has.

…In many cases, armoring can temporarily protect land — and structures — from erosion. But …armoring puts a wall between the upland shore and the water, creating a disconnect and often loss of important habitat such as wetlands. A National Oceanic and Atmospheric Administration (NOAA)–funded study found that shoreline hardening, particularly rip-rap, was associated with a reduced abundance of vegetation even below the water’s surface, such as the eelgrass that shelters juvenile fish, crustaceans and shellfish and helps ecosystems function in other ways. Along beaches with seawalls, researchers find less diversity in fish and invertebrates….

Some 14 percent — or 14,000 miles (23,000 kilometers) — of U.S. tidal shoreline is currently behind some form of shoreline armoring, put in place by both local and federal governments and private landowners. This number is projected to grow as sea levels rise and more severe storms give shoreline property owners more to worry about and as more properties are built in shoreline locations that are vulnerable to erosion. If trends continue, researchers estimate up to one-third of U.S. shorelines could be armored by 2100. 

…the U.S. Army Corps of Engineers, known in the past for canals, dams and other distinctly “hard” structures, has been supportive of the concept and in 2017 issued a streamlined permit specifically for living shoreline projects. The Department of Defense has used hybrid living shoreline techniques to stop erosion while improving habitat at several sites, such as installing shell-based reefs for oysters at MacDill Air Force Base in Tampa…

….According to research published last year by University of California, Santa Cruz, civil and coastal engineer Siddharth Narayan and colleagues, coastal wetlands have protected many properties from flood damage during storm events, specifically helping property owners avoid US$625 million in direct flood damages during Hurricane Sandy. The researchers estimate a 16 percent average reduction in annual flood losses — and up to 70 percent in some locations — in Ocean County, New Jersey, due to the presence of salt marshes, indicating that wetlands help protect shorelines outside major storm events, too.

Additionally, salt marsh meadows may help slow climate change — one of the drivers of some storms — by storing carbon dioxide. According to NOAA researcher Jenny L. Davis and colleagues, salt marshes can store more carbon per acre over the course of a year than mature tropical forests….

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