Scientists worry that the Chesapeake’s natural shoreline is turning into a wall threatening wild life.

Categories: Nature

As "progress" comes to Southwest Washington, the natural shoreline that is home to crabs, fish and other organisms is being compromised by the construction of concrete walls meant to contain the water.

On the banks of the Potomac River, construction cranes that look like metal dinosaurs tower over Southwest Washington. They swivel in all directions, delivering concrete and other heavy material to workers building a large development behind a steel-and-concrete wall that holds back the water.

Within two years, the Wharf will begin emerging as a playground of trendy apartments, shops and entertainment venues. But below the river’s surface, animals that depend on vegetation in the water may continue to struggle, marine scientists say.

The Wharf is part of the great wall of the Chesapeake Bay. Because of development along the bay and its rivers, vast swaths of soft shorelines have been turned into stone. The spread of what scientists call “the armored shore” is depriving young fish, crabs and other organisms of food and shelter. And it is yet another reason why life in the bay is disappearing, according to new research funded by the National Oceanic and Atmospheric Administration.

Houses, offices, bike paths, marinas — and walls built to protect them from erosion and rising sea levels — are replacing marshy shores, uprooting plants that young fish, crabs and other organisms use for food.

Half of some estuaries in Baltimore, Norfolk and the District are hardened by walls, said Thomas E. Jordan, a researcher for the Smithsonian Environmental Research Center who led the NOAA project that examined the impact of changing shorelines.

Much of the transformation took place years ago; the waterfront in Southwest, for example, was hardened decades ago as part of its long-time use as a port and then as a food-and-entertainment district.

The Wharf project underwent a review by the Army Corps of Engineers and other government agencies to help “ensure that the construction is sensitive to the existing habitat and species,” said Matthew Steenhoek, vice president of development for PN Hoffman and Associates, the builder. In addition, he said, the project will include some floating wetlands that will “offer opportunities for wildlife habitat and aquatic vegetation.”

But few armored shores in the bay watershed include that feature. And as the pace of shore-hardening throughout the bay increases, researchers say, so does their understanding of its sometimes detrimental effects.

If the trend continues, numerous species in the bay will continue to decline — despite an ongoing federal cleanup plan that seeks to restore the nation’s largest estuary to health by reducing millions of tons of deadly nutrient pollution, scientists say.

That multibillion-dollar bay cleanup, launched by the Environmental Protection Agency five years ago and scheduled to end in 2025, is the largest of its kind in U.S. history.

The bay estuary contains dozens of micro-estuaries in rivers and creeks that serve as nurseries for hundreds of animals, including fish that start out tiny and hide in grasses before growing and venturing out into the Atlantic Ocean. The bay is key to the health of marine life all along the Atlantic shore.

Years before the current cleanup began, the District and six states in the bay watershed — Virginia, Maryland, West Virginia, Delaware, Pennsylvania and New York — tried to limit pollution but failed to improve the water quality.

Marine biologists noticed years ago that submerged aquatic vegetation seemed to decline near hardened walls. When they tried to better understand the problem, they realized there was a dearth of sound research.

The NOAA-sponsored study of hardened shorelines was undertaken by the Smithsonian center and six other research institutions. It found that the bay’s problem is bigger than the polluted run-off from cities and farms.

Jordan said the region’s population explosion, and the hardening of shorelines that often accompanies development, helps to explain why the states’ pollution-reduction effort fell short.

When the EPA years ago studied what was hurting the bay, it focused almost solely on nutrient and sediment pollution, which can lead to giant, oxygen-depleted areas called “dead zones” that kill fish every summer. The agency did not consider armored shores as a major factor.

Now, “it’s obvious how much we’re impacting the shoreline,” said Rob Magnien, director of the Centers for Coastal Ocean Science at NOAA. “It’s pretty rampant here in the Chesapeake and other areas. We see the effects of hardened shorelines much more, declines in populations of fish. There definitely is a relationship between hardened shorelines and the number of fish species.”

The recent research papers that focused on hardened shores are among 12 produced by the six-year research project. Magnien said they are a message to government planners and others to give more consideration to the impact of human walls on wildlife. “Living shorelines” which use a mix of structures and organic materials such as wetland plants, submerged aquatic vegetation, oyster reefs, and sand and stone, should get more emphasis, researchers say.

An EPA spokeswoman said the agency convened a panel last year that recommended living shores as a way to offset those that are armored. The agency, she said, entered into an agreement with the six bay states to continue reducing pollution to increase “submerged aquatic vegetation and . . . wetlands, which will increase wildlife habitat.”

Hard walls come in many varieties: bulkheads that run straight up and down like a fence; clumps of big, round rocks called rip-rap formed along a slope; and sea walls of developments such as the Baltimore Inner Harbor. More are on the way, the researchers said, as people continue to build — and then protect their property as sea-levels rise.

Walls stir up sediment that clouds the water, blocking sunlight that keeps vegetation alive. Waves that bounce off them disturb the soil and uproot vegetation.

The waves also scoop out soil, deepening the shallow sanctuaries of little fish, such as striped bass, and opening the way for bigger fish to eat them.

“We looked at a lot of sub-estuaries in the Chesapeake watershed, and in the ones we looked at with 50 percent hardening, submerged aquatic vegetation was not recovering,” Jordan said.

“The hardened shoreline may be putting the brakes on improvements we might be getting from the . . . cleanup,” he said.

In the Chesapeake Bay region, submerged vegetation used to cover thousands of acres. It absorbs harmful nutrient pollution — nitrogen and phosphorous — and uses it to provide oxygen. The vegetation would typically die in droves from storms and disease and come back as part of a natural cycle.

But in the late 1960s, the vegetation failed to rally. That coincided with the beginning of the region’s population boom. Since 1950, according to the Chesapeake Bay Program, the population of the region has more than doubled.

Between 1985 and today, the population increased 33 percent, to about 18 million people. Nearly 70 percent of them live in Maryland, Virginia and the District, where the Wharf will complement the Georgetown waterfront as a development feature.

“Submerged aquatic vegetation are hotspots, areas of life where little fish and crabs go . . . to get bigger,” said Donald Weller, another Smithsonian researcher. “We do think it’s important to know the negative effects of armoring as we manage the bay.”

via WashingtonPost

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