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Brian Boutin, a Nature Conservancy biologist, stands protectively over a newly planted bald cypress sapling. Park managers hope to slow the submersion of the Alligator River National Wildlife Refuge. (Lynda Richardson)

Rising Seas Endanger Wetland Wildlife

For scientists in a remote corner of coastal North Carolina, ignoring global warming is not an option

Taking all the data into account, a panel of North Carolina scientists told the state this past spring to prepare for a three-foot rise by 2100, though some regional experts think that estimate is low. (The only places in North America more imperiled are the Mississippi River delta, the Florida Keys and the Everglades.)

Moreover, as the ocean surface warms, some experts predict that stronger storms will hit the Atlantic Seaboard. A major hurricane could bring extreme tides and crashing waves, which can make short work of a wetland. In 2003, scientists in Louisiana predicted that the state stood to lose 700 square miles of wetlands by 2050. Two years later, during hurricanes Katrina and Rita, 217 square miles vanished practically overnight.

Already at Alligator River, salty water from the surrounding estuaries is washing farther inland, poisoning the soil, Boutin says. The salt invasion triggers a cascade of ecological change. The pond pines turn brown and the dying forest is overrun by shrubs, which themselves wither into a dead gray haze. A salt marsh takes over, until it, too, is transformed, first into little jigsaw pieces of land and finally into open water.

Boutin says his team has a decade or less to act. “If we don’t stop the damage now, it’s all going to start crumbling,” he says. “We don’t want the transition to open water to happen so quickly that the species that depend on the land don’t have enough time.” Sea walls and other traditional engineering techniques aren’t an option, he says, because sheltering one portion of coast can speed erosion in another or choke the surrounding wetlands.

Healthy wetlands can keep up with normal sea-level fluctuation. They trap sediment and make their own soil by collecting organic matter from decomposing marsh plants. Wetlands thereby increase their elevation and can even slowly migrate inland as the water rises. But the wetlands can’t adapt if the seawater moves in faster than they can make soil.

The Alligator River project aims to buy time for the ecosystem to retreat intact. Boutin and co-workers hope to create migration corridors—passages for wildlife—connecting the refuge with inland conservation areas. But the relocation of plants and animals must be gradual, Boutin says, lest there be a “catastrophic loss of biodiversity.”

Boutin drives me in a pickup truck to the edge of a vast marsh full of salt meadow hay and black needle rush. Small waves smack the shore. In the distance, across Croatan Sound, we can see the low-slung island of Roanoke. This is Point Peter, the project’s testing ground.

Like many East Coast swamps, Alligator River is crisscrossed with man-made drainage ditches. Workers will plug some of those ditches or outfit them with gates, to keep the saltwater back at least awhile.

There are 40 acres of newly planted saplings—native bald cypress and black gum, which are salt- and flood-tolerant—intended to keep the forest in place a bit longer as the sea level rises. Wolves, bears and other animals depend on the forest, and “we’re holding the line to allow them to use the corridors” to get to higher ground, Boutin says.

Out in the water, white poles stake the outline of an artificial reef that is scheduled to be built soon. Made of limestone rock poured from a barge, the reef will attract oysters and shield the marsh edge from violent waves. This living buffer will also cleanse the water and create habitats for other marine animals, increasing the marsh’s resilience. In other places, the scientists will restore aquatic plants and remove invasive grasses.

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About Abigail Tucker

A frequent contributor to Smithsonian, Abigail Tucker is writing a book about the house cat.

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