Experts: Saltwater can’t be stopped, but we can adapt

CAMBRIDGE, Md. — The road through Blackwater National Wildlife Refuge on Maryland’s Eastern Shore could be called Ghost Tree Way for the story it tells about howinvading saltwater is killing vegetation and redesigning coastal lands.

From the Mid-Atlantic to the Gulf of Mexico, salt is killing groves of trees from the roots up. Advancing water is pressing landowners and farmers into wrenching decisions and challenging conservationists to find corridors for marshes to survive.

Stemming the saltwater invasion is not possible, researchers say. The aim now is to adapt to the continued resculpting of coastlines by finding crops that can thrive with salty feet and by maintaining marshes as long as possible for their many benefits, including reducing property damage during increasingly frequent storms.

Salt is the leading edge of climate change, an early harbinger threatening millions of dollars worth of storm protection as well as coastal ecosystems like Blackwater’s.

In 28,000-plus acres between the Atlantic Ocean and Chesapeake Bay, Blackwater encompasses a half-dozen ecosystems of the Chesapeake region, rivers, wetlands and forests. Since its founding in 1933, Blackwater has lost over 5,000 acres of its marsh lands to open water as the refuge basically collapses from within.

As saltwater intrudes from below and pours in from above as seas rise, forests die off, replaced by marshes and, eventually, open water.

Sea rise at Blackwater is accelerated because of subsidence along the MidAtlantic that began after the last ice age. The sped-up transition has created more of one ecosystem — about 3,000 acres of upland marsh — at the expense of forests.

“Blackwater is a living case study of the impacts of sea level rise. People come here to see dead forests right in front of their eyes,” said Matt Whitbeck, Blackwater’s supervisory wildlife biologist, gazing out over a dying marsh and tree skeletons on the horizon.

Tree after tree, Blackwater’s oaks, maples and American sweetgums have succumbed to the saltwater, leaving stands of the last to go, loblolly pines, dead and bleaching in the sun.

South and east of Blackwater, on Maryland’s lower Eastern Shore, tree loss is so widespread that the Maryland Department of Agriculture classifies saltwater intrusion as a pest — along with the gypsy moth, emerald ash borer and other hostile invaders.

Surveying forests by air in 2017, the state of Maryland found 13,096 acres of forest in four Shore counties affected by saltwater.

A year later, aerial surveys over the same territory showed an increase in mortality; saltwater was afflicting 41,094 forest acres — the majority in Dorchester County, where Blackwater is located.

“I’ve been here 37 years and seen dramatic results from so much saltwater,” said Scott Daniels, a Dorchester Countybased forester at the Maryland Department of Natural Resources. “I don’t think this area will ever again produce another quality stand of timber.”

Trees absorb water through their roots. Salt reverses the process, drawing water from the plants, disrupting the flow of minerals and the capacity to convert light to energy. Even small doses of saltwater stunt growth, researchers say.

Farming has made it worse. In North Carolina, research by ecologist and biogeochemist Marcelo Ardón shows how saltwater travels the ditches and canals dug over the years to drain freshwater from croplands. Now, the ditches carry saltwater inland from storms and invading seas, killing trees before poisoning farmland.

Rick Savage, a former wetlands researcher for the state of North Carolina, said that deeply ingrained farm practices are tough to overcome.

“The mindset of too many people on the coast is that we’re getting flooded and we need more ditches, because that’s what we’ve always done in the past,” said Savage, founder of the advocacy group Carolina Wetlands Association.

But those wetlands offer value.

A study published in March in the proceedings of the National Academy of

Sciences estimated the value of a square kilometer of wetlands at $1.8 million a year — for storm protection alone. A study in Delaware two years ago valued the wetlands along its coast at $1 billion to $3 billion a year — factoring in benefits to water quality, recreation and tourism.

The U.S. Fish and Wildlife Service estimated Blackwater National Wildlife Refuge contributes nearly $8 million to the local economy, factoring in jobs, tax revenue and spending by 223,000 visitors.

As rising water floods in, Blackwater is devising ways to keep marshes alive, prolonging their many benefits, including storm protection and storing carbon.

Four years ago, refuge managers began a project to raise the elevation of 40 acres of deteriorating marsh. Using money from a hurricane relief fund, contractors sprayed the acreage with 26,000 cubic yards of sediment dredged from the Blackwater River, then replanted it with native grasses. In September, drone footage showed the marsh to be lush with foliage.

Yet that strategy, called thin-layering, is likely too costly to be widely accepted. At Blackwater, the price tag was $1 million.

A better strategy, scientists say, is paving the way for new marshes as old ones convert to open water. At Blackwater, the U.S. Fish and Wildlife Service added 2,700 acres of private land to its marsh-migration resiliency plan. In February, work began to transform the land into marshes.

Blackwater purchases are paid for in large part by the sale of Federal Duck Stamps, $25 conservation revenue stamps produced annually by Fish and Wildlife that support wetlands protection by purchasing and leasing land or acquiring easements. In June, the purchase of a 438-acre tract 10 miles to the east extended the refuge. About half tidal marsh and half forest, the land is ripe to accommodate new marsh created as rising seas submerge old wetlands on their rush inland.

The federal agency made its purchases despite pockets of local opposition, said Marcia Pradines, a Fish and Wildlife biologist who manages Blackwater and other refuges in Maryland and Virginia.

“Not everybody loves the government buying up land,” she said.