At Blackwater Refuge, Rising Sea Levels Drown Habitat

The view from the observation deck over a meadow of brown marsh grasses would make a nice postcard. Eagles roost on tall pines, muskrats burrow in mounds of mud and straw, and black ducks splash in a pond.

But on a cold and drizzly day, Matt Whitbeck surveys the landscape with concern.

Beyond the marsh is what the Fish and Wildlife Service biologist calls “Lake Blackwater.”

“It’s this beautiful body of open water,” he says. “When you really start to think about why this is here, it’s disturbing.”

The area was once an uninterrupted prairie of aquatic grasses. But waters have risen more than a foot over the past century, drowning the native plants and converting nearly eight square miles of marsh into open water.

Models suggest most of the unique ecosystem will disappear by 2100.

Across the water, conservationists are aiming to at least delay that fate. Their plan: literally raising the marsh.

Mud pumped from the bottom of the Blackwater River splattered across 40 acres of marsh like an oil geyser, raising its elevation inch by inch.

Ellicott 460SL Swinging Ladder Dredge

Ellicott 460SL Swinging Ladder Dredge

After the 26,000 cubic yards of the sediment settles and hay-like saltmeadow cordgrass sprouts through it, Whitbeck hopes the wetland draws saltmarsh sparrows back to nest in significant numbers for the first time in years.

Conservationists say the effort should protect against the monthly flooding that overwhelms the marsh. But their ambitions are grander: In the long run, they think the boost will help the marsh to flourish and build itself up, so it can keep pace with rising sea levels for at least a few more decades.

It is the first large-scale effort of its kind to combat sea level rise in the Chesapeake Bay.

Dredge material is applied to the wetlands at Blackwater National Wildlife Refuge to help them keep up with rising sea levels.

Dredge material is applied to the wetlands at Blackwater National Wildlife Refuge to help them keep up with rising sea levels.

“We want to keep these marshes around for the biodiversity and fisheries and their value as a storm-surge buffer,” said David Curson, director of bird conservation for Audubon Maryland-DC.

The federal government established the Blackwater refuge in 1933 to serve as a stopover point for migrating blue-winged teals, ospreys, black ducks and Canada geese.

It has become an important Eastern Shore resource, drawing more than 180,000 tourists each year. Its marshes protect communities from flooding and erosion, and they provide vital habitat for young broods of commercially valuable fish such as menhaden and flounder.

But since 1938, the 29,000-acre preserve has lost about 5,000 acres of marshland, according to an analysis of satellite data by a team at Salisbury University in 2009.

The changes started with Swiss cheese-like gaps in the marsh, as floods gradually overwhelmed the flowering bulrush, cordgrass (more commonly known as salt marsh hay) and other grasses.

Those grass varieties evolved to handle the monthly high tides that come with every full moon, but they can’t survive for long if their roots are waterlogged. The flooding stunts the growth of their roots and limits the buildup of peat — soil-like gunk made of decaying plants — that forms the marsh floor.

Curson said the changes are obvious even before marshland gives way to open water. On annual bird-counting surveys, he has grown used to taking a step through marsh grass only to suddenly find himself waist-deep in mud.

During last year’s count, he said, it happened something like five times more often than in the past.

“I could feel that the root mats had disintegrated that much more,” he said.

As waters rise — as a result of climate change, and also because the Eastern Shore has been slowly sinking since the last ice age ended 10,000 years ago — new marsh areas are developing where forests once stood.

They are marked by isolated dead tree trunks known as snags, which can be dangerous for small marsh creatures, because they serve as perches for bald and golden eagles.

The rising water has added about 3,000 acres of wetlands to offset the losses, but conservationists say the new marshes aren’t the same. They’re often invaded by Phragmites, upland tall grasses with less extensive root systems than native plants.

Phragmites can’t support the same diverse ecosystem as native species because they don’t have the flowers, seeds and roots that support marsh birds, fish and rodents.

The changes are blamed for drastic declines in the populations of birds such as the saltmarsh sparrow and black rail.

The latter, a tiny bird known for its secretive nature, has declined 85 percent since the early 1990s, according to Audubon. It’s been on Maryland’s endangered species list for more than a decade.

The new marshland “doesn’t preserve the quality of habitat for the wildlife that depend on it,” Whitbeck said. “If you’re a black rail or a saltmarsh sparrow, there’s no home for you in a Phragmites-dominated marsh.”

As Blackwater officials and wildlife advocates began to analyze conditions over the past several years, they realized they were not going to be able to restore the landscape to its pre-Colonial state or reverse the impact of rising seas.

“There was little we could do to halt that,” said Erik Meyers, vice president for climate and water sustainability for the Conservation Fund. But “there was a lot we could do in terms of slowing down the pace in strategically selected areas.”

They have shifted their goals to focus on how to best adapt to the changes that have already occurred, and those to come. They’re looking first to preserve what they can.

Near the public boat ramp known as Shorter’s Wharf, the marsh is going to look a lot worse before it gets better, Whitbeck said.

Until November, it looked like pristine marshland. Now it looks like a barren mud flat.

For about six weeks, a pipeline stretched from a dredge in the narrow Blackwater River channel, across a marshy bend in the waterway, to Shorter’s Wharf. It spewed black sludge.

That material was pumped from a sweet spot in the river bottom, home to a combination of sand, silt, clay and decomposed organic matter.

Albert McCullough, an engineer working on the marsh project, called it “a Goldilocks type of material” — light enough that it can be easily sucked up but heavy enough that it will stay where it’s sprayed.

A wooden marker indicates the elevation that engineers targeted, 30 centimeters above a benchmark height established by the U.S. Geological Survey. That level is based on USGS research into marsh grass growth at varying water levels.

“This is a way of prolonging the existing marsh but also building up its ability to build its own elevation,” Whitbeck said.

The $1.1 million project is being funded with federal grants for coastal resiliency projects offered after Superstorm Sandy hit in 2012. It is a collaboration between the Fish and Wildlife Service, the Audubon Society and the Conservation Fund.

The scientists expect native grasses will sprout through the mud within a year or two. They might plant more to fill in gaps.

It’s not the first time they’ve tested the approach: They’ve used it to fill in smaller holes in the marsh or to bolster its edges in years past. But it’s the largest example of marsh-raising they’re aware of in the Chesapeake, on par with similar efforts on the Gulf Coast.

Conservationists are also employing other approaches to protect the marsh. They’re still on guard for nutria, the invasive rodent that has been eradicated from the preserve but could reappear and eat up vital marsh roots. They have deployed pesticides to fight the spread of Phragmites.

And when federal officials announced the acquisition of 400 acres along the Nanticoke River from The Nature Conservancy, they emphasized that the land is attractive because much of it isn’t prime marshland — at least not yet.

“It’s not where the best habitats are now but where they’re going to be in 2050,” Whitbeck said.

Sarah Wilkins is coordinator of the Chesapeake Bay Sentinel Site Cooperative, a network of sea level monitors.

Sea levels in the Choptank River, the closest monitoring point to the Blackwater refuge, have risen by an average of 3.69 millimeters per year since 1943, Wilkins said. From 1985 through 2015 alone, it increased by more than 5 millimeters a year — among the highest amounts in Maryland during that time.

The Maryland Climate Change Commission estimates sea levels will rise 1.4 feet during the first half of the 21st century, and another 2.3 feet in the second half.

Zoe Johnson, who coordinates climate change adaptation for the Chesapeake Bay Program, said it will take more than one tactic to adapt to such a dramatic shift.

Though inundation might be inevitable, she said, the marsh is worth the investment.

Maryland Department of Natural Resources analysts say salt marshes are among the most economically valuable ecosystems in the state. They help protect against inland floods, provide habitat for commercial fish species and filter pollution — functions that are thought to be worth several thousand dollars per acre.

After years of watching the effects of climate change wash through the marshes, Blackwater conservationists say it’s time to try to protect that resource. The Shorter’s Wharf project is a first step.

“We’re in a position where good, bad or otherwise, we’re going to be able to learn,” Whitbeck said. “So the next time an opportunity comes up, we can do it even better.”


Source: Baltimore Sun