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
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.
So far, the results are encouraging. Birds have returned, including a variety of ducks that hunters feared were gone for good. Eels, bass, crabs, perch, flounder, and other fish are increasing in numbers. But the project is still young. “In terms of the long-term trajectory, it’s too early to tell,” Sommerfield says. “It will be another 10 years to know if the grasses are growing in the right location at the density to keep the landscape stable.”
On a spring afternoon with an easterly wind blowing water into the marshes, Rizzo pulls over on Prime Hook Road, the refuge’s central artery. An electronic sign at the road’s entrance that warns drivers when it is flooded hasn’t blinked since the restoration; the marsh is once again naturally absorbing high tides and storm surge.
“It’s pretty amazing we have as much regrowth as we do,” Rizzo says. Small circles of Spartina alterniflora that sprouted naturally dot the dark mudflats. Along the channels, grasses grow thicker. Phragmites, a non-native invasive grass, grows along the edges of the Spartina stands, but it’s been sprayed with herbicide, one of the few nods to continuing intervention.
“Our primary objective was to set the table to allow the system to adjust itself and work based on normal coastal dynamics,” says Rizzo. “What we’re doing now is sitting back and watching.”
Source: Yale Environment 360