Alligator River Refuge Rolls Back From Rising Sea
As coastlines are battered by rising seas, staff at North Carolina’s Alligator River Wildlife Refuge look for ways to make an orderly retreat.
Standing on a beach on the Albemarle Peninsula in North Carolina, Brian Boutin, a Nature Conservancy biologist, points to a rusted piece of rebar with a green tag a few inches from the water’s edge. “That was our original marker to show what was happening here three years ago,” he says. “It was 20 meters from the shoreline. Now, it is the shoreline.”
To the south, waves hit the shore and explode into the air, little eruptions of erosion. To the north, the waves break, but more gently. Offshore, Boutin and his Nature Conservancy colleagues have built 500 feet of reefs designed to dissipate wave energy and slow the erosion caused by higher sea levels. “Once we put in those reefs, we really had a big change,” he says. “We were getting 5 to 7 meters of shoreline erosion annually. But it went to less than a meter.”
The late-winter wind howls from the east, whipping up whitecaps on the Croatan Sound that batter the curving coast here at Point Peter, in North Carolina’s Alligator River National Wildlife Refuge. There are alligators in the refuge, and river otters, black bears, and bald eagles. This is the only place where red wolves exist in the wild. Thirty-five years ago, only a few were still alive. Biologists captured 17, bred them, and in 1987, released four pairs in the refuge. More than 100 roam the refuge today (it was the first successful wolf reintroduction).
Sea level has been largely stable for about 5,000 years. Coastal areas changed over time, but they changed slowly. Today, melting glaciers and rising sea waters have accelerated the transformation, making larger areas vulnerable to flooding, erosion, saltwater intrusion, and loss of wetlands and biodiversity. The Nature Conservancy’s man-made reefs are part of a pilot project at the 154,000-acre refuge designed to slow things down and give the coastal ecosystem a chance to adapt. Working with the U.S. Fish and Wildlife Service, Boutin and The Nature Conservancy crew are using an array of simple restoration techniques to postpone the inevitable.
The Nov-Dec 2011
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The project requires improvisational science, science on the fly. Forget the long-term studies.
“It’s classic adaptive management, but on a larger scale and shorter time frame,” Boutin says. “We don’t have time to sit there and monitor something for 20 years. … We’re trying to figure out the best techniques as we move forward, and adjust for each location.”
If it works here, similar strategies could be used along the shoreline from Maine to Texas. The North Carolina coast is considered one of the most vulnerable areas in North America, along with the Mississippi Delta, and the Florida Keys and Everglades.
So workers are filling man-made drainage ditches and installing gates in others in an attempt to slow the advance of salt water. They have planted 40 acres of young trees, salt-tolerant species such as bald cypress and black gum to preserve forest cover for the wolves, bears, and other animals. They are building oyster-shell reefs to reduce wave energy, slow currents, and stave off shoreline erosion.
And The Nature Conservancy is trying to connect this area with conservation lands in the interior so protected species such as the red wolf will have a place to go when the waters rise. “We’re looking to try to maintain a high-quality wildlife habitat for a little bit longer,” Boutin says. “We’re trying to buy a little bit more time.”
Dennis Stewart, a biologist with the Fish and Wildlife Service who has been watching changes at Alligator River for 17 years, says the land is visibly different from when he arrived. “When you fly over the refuge, you can tell there’s thousands of acres that are under stress.”
“These lands are going to be inundated,” he says. “We’re going to see some habitat changes occur.” But the work under way is meant “to reduce that rate of change, to ensure we keep biodiversity, to ensure that we keep the ecosystem services from the lands that we depend on — and to not allow a rapid simplification of the ecosystem, which could have large-scale impacts on people.”
As Boutin walks along the beach at Point Peter, he reaches down to pick up a handful of soil. It’s pocosin peat, common to the area. As the water intrudes, the peat breaks down, increasing the rate of land subsidence and releasing methane into the air, which fuels warming. “It’s a self-feeding system,” he says, “warming, sea-level rise, inundation, degradation of the peat.”
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Projections of sea levels for the next century vary widely, from increases of 7 inches to as much as 7 feet, depending on how much polar ice melts. Orrin Pilkey, professor emeritus of earth sciences at Duke University, has studied sea changes since the 1970s and argues that North Carolina should plan for a rise of 7 feet.
The National Oceanic and Atmospheric Agency says of the 22,054 miles of U.S. coastline, about 50 percent — including more than 70 percent of the North Carolina coast and 82 percent of the Virginia coast — is “highly” or “very highly” vulnerable to sea-level rise. (The Virginia and Carolina coasts have large areas that are 9 feet or less above sea level.) Models have shown even a 12-inch increase could flood up to 469,000 acres of the Albemarle Peninsula; a 20-inch rise might inundate nearly 750,000 acres, more than a third of the peninsula.
Because the effects of sea-level rise are expected to be visible relatively quickly along the North Carolina coast, the work at Alligator River is being watched closely by academic researchers and environmental organizations. “Every national wildlife refuge from Cape May, New Jersey, to Pea Island, North Carolina, will suffer the same fate,” says Skip Stiles, executive director of Norfolk, Virginia-based Wetlands Watch. “This means that all of the tidal wetland and shorebird habitat along the Atlantic Flyway goes away at the same time. New wetlands can form behind the existing ones, but you’ve got to get the folks who own that land to let it flood and not put subdivisions on it.”
A 2009 U.S. Environmental Protection Agency report noted that many marsh islands along the mid-Atlantic and in the Chesapeake Bay have shrunken or have been lost entirely. Further loss threatens island-nesting birds such as terns and black skimmers. Loss of tidal flats, the report added, could increase crowding among foraging birds in the remaining area, starving enough of them to significantly reduce their numbers. On Chesapeake Bay, the largest estuary on the Atlantic coast, 13 islands have disappeared beneath the waves, according to a National Wildlife Federation report. Some 66 percent of commercial fishes, that report noted, including Atlantic menhaden, bluefish, spot, mullet, and rockfish, depend on coastal marshes for nursery and spawning grounds.
“I think places like Alligator River, where you have early signals on this, need to pioneer this stuff and see if there aren’t ways to hold on as long as we can and stage an orderly retreat,” Stiles says.
But making an orderly retreat will be difficult in many areas, requiring government officials to make hard choices. Only 9 percent of the lowest land on the Atlantic coast has been set aside for conservation, according to an independent report co-written in 2008 by Jim Titus, an EPA expert who has been considering the dangers of sea-level rise for three decades.
On a website Titus maintains apart from the EPA (www.risingsea.net), he summarizes the problem:
Most people assume that their own community should be protected. But that poses a problem: ecosystems need to migrate inland. And as a society, we may not be able to protect every home in the coastal floodplain even if there weren’t environmental problems — it costs a lot of money and having too many people living below sea level just seems like a bad idea. Sooner or later, we are going to have to decide which lands to protect and which lands will yield to a rising sea. And that will require drawing lines on a map — lines that will be controversial, costly, and require much debate, discussion, and negotiation.
The study used discussions with more than 100 local governments to create provisional maps reflecting officials’ best guesses about lands likely to be protected and those likely to surrender to rising seas. A 166-page portion about North Carolina concludes “there is no explicit plan for the fate of most low-lying coastal lands as sea level rises.”
Federal programs discourage the destruction of existing wetlands, but do little to allow wetlands to migrate inland. A 2009 EPA report, “Coastal Sensitivity to Sea Level Rise: A Focus on the Mid-Atlantic Region,” with Titus as the lead author, concludes: “A large-scale landward migration of coastal wetlands is very unlikely to occur in most of the Mid-Atlantic unless a conscious decision is made for such a migration by a level of government with the authority to see it through.”
Those low-lying coastal wetlands provide important and valuable ecosystem services. “Acre for acre, they are as productive as tropical rainforest,” Stiles says. They improve water quality by filtering out sediments and nutrients, and they mitigate storm surges by storing flood waters.
Titus points out that holding back the sea (with an increasing number of seawalls) will make economic sense in developed urban areas. The question will be what to do in less developed areas. Protecting private property will become increasingly expensive. One solution, he says, may be to permit development on private property for a period of time before surrendering to the water, through the use of “rolling easements,” which have been used along the shores in New England, South Carolina, and Texas. (These easements essentially prohibit home builders from protecting the shores, and may require the removal of structures from the shores as the seas rise.) “Putting up a house doesn’t mean it stays there for 200 years,” he says. “It’s an option that’s out there and is easier to consider than going to existing communities and telling owners their homes’ days are numbered.”
Another EPA report, written by Titus, concludes: “A large rise in sea level would eventually require communities to either hold back the sea or move inland. Neither of these options seems feasible today, given what we know about the forces of nature and human nature. Yet those are the only logical possibilities. If some lands must give way to the rising sea, the economic, environmental, and human consequences could be much less if the abandonment occurs according to a plan rather than unexpectedly.”
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So at the alligator river wildlife refuge, work is under way to see how human intervention might slow the effects of sea-level rise and allow the ecosystem to migrate inland.
Last spring, not far from the beach now protected by the man-made reefs, workers operated a backhoe to make the final adjustments to a muddy ditch carrying water to the sound through a series of huge pipes with check valves. The corrugated metal pipes, with expanding and contracting conical valves at the end, are part of a complicated attempt to restore some of the natural hydrology, allowing scientists to control fresh water flowing out of the refuge.
Closer to the beach, they have plugged ditches to help hold back the intrusion of salt water, which threatens plants that need fresh water for reproduction. At one time, nearby rivers deposited sediment that helped build up the soil, but the 96 miles of roads that were constructed over the decades act as dikes, preventing that accretion. Bringing in fresh water will allow trees and grasses to thrive, building up the organic soil. To re-create the more natural sheet flow of water, Boutin’s team is constructing spillways under roads so water can flow to the other side. The water in ditches, he says, is low quality, anoxic, uninhabitable by fish, oysters, and other marine life. “We want to keep [fresh] water on the land because that’s how the land wants it,” Boutin says. “Ideally, we would completely fill in all the ditches, but that’s just not possible economically.”
In the long run, saltwater intrusion is inevitable, so at Point Peter, The Nature Conservancy is planting black gum and bald cypress trees — 40 acres so far — that are salt-tolerant and provide cover for the red wolf and black bear. The trees won’t keep back the water, but they will buy time for species to migrate by creating habitat. “In the long run, when the sea begins to invade these areas, we’ll still have a functional ecosystem for a while before it transitions into an estuarine habitat,” Boutin says.
He notes a nearby stand of phragmites, a camel-colored reed that can spread as much as 16 feet per year and pops up anywhere there’s been a disturbance. In the past, phragmites were seen as an invader to be eradicated. Now, the plant symbolizes the trade-offs when dealing with a compromised ecosystem. “Although it’s an invasive species, it does one thing well: It holds onto land,” Boutin says. “The question is, do we get rid of phragmites and replace it with the native vegetation that should be here, or do we let it go because it’s holding onto the land? It poses a lot of counterintuitive restoration-type questions. Obviously, we’re not going to encourage any spreading, but by removing it, are we actually increasing vulnerability?”
Trying more than one option is a part of the plan. On the beach, Boutin points to 400 feet of offshore reefs built from limestone marl; another 100 feet were built using bags of oyster shells. A few miles away, students from the University of North Carolina at Greensboro spend a spring break laboriously filling one mesh bag after another with shells. The Nature Conservancy is testing which material works best to slow erosion, but also which is more practical. Shell bags are labor-intensive but — if there are enough volunteers — are cheaper than trucking or barging in marl.
Point Peter is a demonstration project, a laboratory where people can view the strategies, and The Nature Conservancy can closely monitor progress. “There’s more than we can do in a lifetime,” Boutin says. “But we want to go about it smart, knowing how we can have the largest impact on the land.” Similar pilot projects are already beginning at other refuges in North Carolina, and the Alligator River team is in talks with state, federal, and nonprofit owners of other natural areas.
Ultimately, because of the scope of sea-level rise, Boutin thinks government will have to step in and fund projects nationwide, projects based on what works at Alligator River. That will be expensive, he notes, but not as expensive as doing nothing. Effectively managing conservation lands will protect the services they provide, including mitigating the damage from coastal storms. So that means the next step for Boutin and others involved in the project is making the dollars-and-sense case.
“We’re in the process of doing that economic analysis right now,” he says. “What we’re finding is these conservation lands are integral to the livelihoods out there, whether it’s keeping the highway corridor intact for tourism, whether it’s fishing, industrial and recreational, or hunting for people who use the land south of Alligator River, which depends on species moving back and forth between the refuge and private lands.
“The recreation value, tourism value, hunting and fishing value, and storm protection value is huge,” Boutin says.