In the waters of Albemarle Sound, baby oysters spell hope for the future.
Albemarle and neighboring Pamlico Sound form the second-largest estuary in the lower 48 states of the U.S. Tucked behind North Carolina’s fabled Outer Banks, millions of acres of marsh along the sounds once provided habitat for the abundant shrimp, crabs, and fish that still sustain local livelihoods.
Now a range of environmental threats have destroyed half the wetlands, and climate-driven sea level rise threatens to take the rest.
More and more scientists expect at least three feet of sea-level rise by the end of this century, and some now warn that the seas could rise six feet or even a devastating 15 feet. But even the limited sea-level rise to date is having devastating impacts in Albemarle Sound.
Rising salinity in thousands of miles of ditches dug through the wetlands is killing the trees that hold together the landscape. The salt also dissolves the peat that passes for soil here.
Without the trees and with the soil literally slipping away, the ditches can widen into lakes, pocking the landscape like holes in Swiss cheese. Meanwhile, the deepening water of the sound allows waves to reach the shore, causing erosion that can drive the shoreline back tens of feet every year.
This is where the baby oysters come in. In 2009, scientists from The Nature Conservancy installed artificial reefs made from limestone rocks or bags of oyster shells offshore of a small section of Albemarle wetlands. Oyster larvae settling on these reefs find them a suitable place to grow, and eventually the artificial structures will bear a living mantle of oysters, allowing the reefs to grow up as sea-level rise continues (to a point).
In their first year, the reefs appear to have cut erosion by more than 90 percent. Meanwhile, the Conservancy and the U.S. Fish and Wildlife Service are installing water-control structures to stop salt water moving up the ditches. And Conservancy volunteers have planted salt-tolerant native trees in areas where the tree cover has died back. Like the baby oysters, the baby trees will grow with time, providing long-lasting erosion-control benefits.
Our efforts to date are pilot projects to show the benefits that nature can provide. The challenges of the future include building this work up to a point where there are benefits for a biologically significant swath of wetlands, and demonstrating that helping nature provides benefits for people too.
For example, protecting the wetlands of the Albemarle peninsula helps prevent saltwater from intruding into farmland, and helps protect the foundations of the highways that carry millions of tourists to the beaches of Nags Head, Kitty Hawk, and other towns on the banks.
Off shore, the wetlands improve fisheries in the sounds and in the open ocean beyond the Outer Banks, while protecting water quality by keeping mercury and nitrogen trapped in the peat. Not to mention the unseen benefit of preventing still more global warming that would be triggered by the destruction of the millions of tons of peat that underlie the wetlands.
Some of these benefits accrue to local residents, others to tourists, and still others to all of us — in the U.S. and even the world. It all begins with the oysters.
Frank Lowenstein is climate adaptation strategy leader at The Nature Conservancy
Photo by: Frank Lowenstein/The Nature Conservancy (A dead oak by the side of Albemarle Sound, North Carolina. It was killed by rising sea level that inundated its roots in salty water.)
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