Coastal Recovery: Bringing a Damaged Wetland Back to Life
An ambitious wetlands restoration project is underway on Delaware Bay, where scientists are using innovative methods to revive a badly damaged salt marsh. The project could be a model for other places seeking to make coastal wetlands more resilient to rising seas and worsening storms.
Standing atop a 10-foot dune at the Prime Hook National Wildlife Refuge on Delaware Bay, refuge manager Al Rizzo describes one of the largest and most complex wetlands restoration projects ever mounted, a $38 million attempt to return 4,000 acres back to what nature intended.
Contractors hired by the U.S. Fish and Wildlife Service dredged more than 1 million cubic yards of sand from Delaware Bay to create 2 miles of beach and barrier dune that had been washed away by a series of storms beginning in 2006 and culminating with Hurricane Sandy in 2012. To stabilize the recreated dune, workers then planted half-a-million American beachgrass plugs and erected 10,000 feet of fencing. Down the beach, Fish and Wildlife staff are enclosing the nests of piping plovers, a threatened species that started breeding at the refuge only three years ago.
Inland, new plantings of Spartina patens — a native salt meadow grass that’s sensitive to water levels and salinity — poke out of the ground, an indicator of a healthy marsh. And throughout the Prime Hook wetlands, dredges have carved 25 miles of channels in an attempt to restore the natural flow of salty and brackish water. The 600,000 cubic yards of sediment produced by that project were cast onto the banks, creating sand flats that are being colonized naturally by Spartina alterniflora, another native grass.
Scientists say the project is a living experiment to understand what works and what doesn’t in wetlands restoration.
The goal of this work is to reverse the damage created by an ill-conceived project in the 1980s that aimed to convert Prime Hook’s salt marsh into a largely freshwater impoundment system, in part to attract more ducks, geese, and other birds for hunters and birdwatchers. But what Rizzo and others see at Prime Hook is more than the resurrection of a single marsh. They see a model for restoring vital wetlands worldwide by taking design cues from nature to recreate a resilient ecosystem — an increasingly vital task as climate change threatens coastlines with rising sea levels and stronger storms.
Scientists working on the Prime Hook project say it is a living experiment to better understand what works and what doesn’t in wetlands restoration. To that end, they have developed a sophisticated monitoring system that records water flow, dissolved oxygen levels, sediment flow, and other key markers. The goal is to rebuild a healthy tidal marsh with meandering channels, lush salt-tolerant grasses, and mudflats that attract a rich diversity of fish and birdlife.
“Every restoration is basically a research project,” says Chris Sommerfield, a University of Delaware oceanographer who is tracking sediment flow in and out of the refuge, a key to building habitat for grasses. “Every site is different. Every time we do a restoration we learn a lot that we can translate into better restoration practices. That’s important because we will be restoring wetlands forever.”
Wetlands are one of the most valuable and diverse ecosystems on the planet. Yet because of development, pollution, and the effects of climate change, they are disappearing at an accelerating rate. A major study released this week on the destruction of ecosystems and the loss of biodiversity said that more than 85 percent of the world’s wetlands have been lost since 1700.
A key element in reversing that trend will be efforts to revitalize degraded marshes and devise strategies for protecting coastal wetlands as sea levels rise. And what researchers have confirmed in recent years is what land managers have been seeing anecdotally: Coastal wetlands, when preserved or restored, reduce flooding and erosion better than hard infrastructure like seawalls and levees. And they do it at a lower cost. In one recent study, researchers found that wetland restoration provided $8 in flood reduction benefits for every $1 invested. The study also found that solutions such as marsh and oyster reef restoration could help prevent more than 45 percent of flood damage over a 20-year period in the Gulf of Mexico alone, saving more than $50 billion.
But that’s only a portion of the value of wetlands. Although they cover less area globally than forests, wetlands sequester carbon more efficiently than woodlands. In a 2018 paper, Sommerfield valued carbon sequestration of tidal wetlands in the Delaware River estuary at $42,000 per square kilometer. The researchers noted that the estuary lost about an acre per day of wetlands from 1975 to 2011.
A quarter of Delaware remains wetlands. Like many states, it has a plan to conserve and restore them. The state is also a signatory to the Chesapeake Bay Watershed Agreement, which seeks to create or reestablish 85,000 acres of wetlands and improve the health of another 150,000 acres in the bay by 2025.
Programs to rebuild wetlands are gaining momentum globally. In Europe, a seven-year project aims to restore wetlands and connect former floodplains along the Danube River. In China, which has seen its wetlands rapidly disappear in the face of soaring economic growth, an ambitious plan has been launched to restore nearly 9,000 acres of wetlands north of Shanghai. In Australia, the government of New South Wales, working with The Nature Conservancy and the Nari Nari Tribal Council, has launched a major project to restore 210,000 acres of wetlands in the Murrumbidgee Valley. In England, an initiative on Wallasea Island is seeking to repair more than 1,600 acres of wetlands by recreating an ancient landscape of mudflats and salt marsh, lagoons, and pasture.
In the United States, the National Oceanic and Atmospheric Administration has created a wetlands Restoration Center, and the U.S. Army Corps of Engineers, long builders of human-centric infrastructure solutions, has begun an Engineering With Nature Initiative.
Humans messing with the hydrology of the Prime Hook refuge had created an unnatural disaster.
Engineering with nature is how Rizzo and Bart Wilson, Prime Hook’s restoration project manager, describe their approach to restoring nearly half of the refuge’s 10,000 acres. The Prime Hook National Wildlife Refuge was established in 1963, and until the 1980s, it remained a healthy East Coast salt marsh. Then, managers decided to convert a portion into a freshwater marsh with large areas of open water to attract more migratory waterfowl, among other things. Tide gates were installed across creeks and a canal, reducing the flow of saltwater from Delaware Bay. Freshwater surface runoff was allowed to increase.
A series of storms starting in 2006 opened breaches in the refuge’s line of dunes, inundating the re-engineered system with saltwater, which killed the marsh grasses and turned a healthy riparian forest inland into a ghostly wasteland of skeletal trunks. A county road running through the refuge to a strip of homes on the beach flooded nearly every high tide. Saltwater crept into nearby farm fields, rendering them useless. The cycle of algae bloom and death led to fish kills.
“It was a stink hole,” Rizzo says. Humans messing with the hydrology of the refuge had created an unnatural disaster.
The current restoration project, funded with federal money through the Hurricane Sandy Disaster Relief Act, involves a long list of state and federal agencies, as well as conservation groups such as Ducks Unlimited, The Nature Conservancy, and the Delaware Nature Society.