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Living Shorelines: Birds and Blue Carbon
We often say that healthy coastal ecosystems can help reduce risks from climate change impacts like sea level rise, more frequent and intense coastal storms, and related erosion, while providing valuable habitat and ecosystem services, like water purification.
A recent study in PLoS ONE offers important new evidence that choosing natural infrastructure to protect our coastlines, over hard armoring like bulkheads and seawalls, adds value above and beyond the primary purpose of erosion control. It finds that living shoreline management approaches can also come with a substantial carbon benefit.
What this study adds to the mix is that, on top of providing wildlife habitat, fish nurseries, and land & water conservation benefits, living shorelines can actually help keep carbon out of the atmosphere by sequestering it as what is called “blue carbon” that is buried for long time periods in tidal wetlands.
Plants take in carbon dioxide in the process of photosynthesis; wetland vegetation therefore assimilates atmospheric carbon dioxide and can store it as underground biomass for centuries.
So marsh vegetation is keeping carbon out of the atmosphere not only by physically holding the shorelines together and slowing carbon losses from shoreline erosion, but also through physiological functions of the plants themselves, as part of the carbon cycle.
The study’s authors point out that tidal wetlands actually sequester carbon at much greater rates than terrestrial ecosystems, like mature tropical forests, because of their high primary productivity and low remineralization rates. This is in contrast to hard armored shorelines, which do not provide carbon sequestration benefits. In fact, if armored shorelines involve concrete, they can have a large carbon footprint, on top of eliminating habitat.
While the primary purpose of constructed living shorelines is to prevent shoreline erosion, studies like this demonstrate that there are additional benefits to living shorelines over hard armored shorelines. These results give us one more reason to encourage the use of natural or hybrid green-gray infrastructure to protect our coastlines, over strictly hard armoring.
According to the study’s authors, this is the first study to evaluate blue carbon sequestration in living shoreline projects. Much of what was previously known about blue carbon came from broader expanses of natural marshes, so much less was known about the potential of constructed living shorelines to sequester carbon.
According to NOAA Director Dr. Russell Callender, “Shoreline management techniques like this can help reduce carbon dioxide in the atmosphere while increasing coastal resilience.”
Living shorelines can also be incorporated into hybrid bank stabilization designs that use some engineered elements combined with native biological materials, getting the benefits of engineered solutions while still getting some of the ecological functions of a more natural system. They can also be designed to keep pace with sea level rise by incorporating wetland processes, which hard armoring does not offer.
The National Wildlife Federation is actively encouraging the use of living shorelines and project designs that take sea level rise into account, through several channels: community outreach and collaborations with scientists and coastal land use planners in the Hurricane Sandy impact area and the Gulf Coast region, as well as advocating for more widespread adoption of living shorelines approaches, via federal permitting processes and the courts.