Is This the Last Generation to Live on New York City’s Wild Fringes?

Don Riepe pointed to the line on the wall five and a half feet above his kitchen floor. That was where floodwaters reached during Hurricane Sandy in 2012.

His home, a humble two-story wooden structure, is decorated with nautical maps, horseshoe crabs and assorted maritime paraphernalia. It sits right on Jamaica Bay, with a small dock at the water’s edge, where he moors his 22-foot boat. He has a spectacular view of the east end of the bay with the spires of Manhattan in the distance.

Mr. Riepe, a former manager of the Jamaica Bay Wildlife Refuge, considers himself blessed to be surrounded by nature and still have all the perks of a big city a subway ride away. But he knows his neighbors’ time there may be coming to an end. During his four decades living in the area, Hurricane Sandy was the worst Mr. Riepe has seen; the flooring and all the electrical appliances on the first floor of his house were destroyed. Since then, during lesser storms and even high tides, he moves his computer and furniture upstairs, where he sleeps — and he hopes for the best.

Mr. Riepe is just one of tens of thousands of residents who live on the wild fringes of Queens, in communities like Hamilton Beach, Edgemere and Howard Beach, where the ocean threatens to encroach as sea level rises and coastal storms intensify owing to climate change. It is also the focal point of a major environmental restoration project that aims to protect the area — and in fact the whole city — by returning salt marshes and sand dunes to their natural states. How this will affect the community of Broad Channel (the only inhabited island in Jamaica Bay) remains to be seen.

Already, Mr. Riepe’s neighbors are scrambling to adjust to their new climate-changed reality — moving their cars to higher ground on high-tide days, and in some cases converting their ground floors into garages and shifting their living quarters upstairs and out of harm’s way. One thing that they are not yet prepared to do, however, is move out.

“People in Broad Channel were born there,” Mr. Riepe said. “They raised their kids there. I mean, it’s a great place to live in New York City. You can fish, you can have a boat.”

The mostly working-class neighborhood (population roughly 3,000) where Mr. Riepe lives is a throwback to an earlier era of detached homes, bungalows and preternaturally quiet streets. “These folks are not going anywhere,” he said.

But that’s not completely true. Mr. Riepe, who nowadays is best known for the bird walks and shoreline cleanups that he leads, fully expects that in 25 or 30 years, sea level rise will make his home and many others like it unlivable. He is 82, and he doesn’t expect to be around then. But for the sake of those who will be, he and his neighbors are banking on a plan to restore the wetlands and to build up the islands in the bay, which they hope will soften the blow of future storms. It will also return some of the natural beauty for which the bay was once known.

Jamaica Bay is an estuary nearly the size of Manhattan that carves into the boroughs of Brooklyn and Queens, and it is far and away the largest natural space within New York City. For Native American tribes like the Lenape, the bay was a “hugely important hunting and fishing grounds,” according to Eric W. Sanderson, who is best known for the Mannahatta Project, which reconstructed Manhattan’s ecological past. He is now conducting a similar survey of the other boroughs.

Mr. Sanderson and a group of city officials recently paid an inspection visit to a restored marsh on the Rockaway Peninsula, an area that used to be filled with rubble, concrete blocks and construction debris. Almost as if on cue, a great blue heron glided past the group noiselessly, creating barely a ripple in the mirror-like waters. A small fenced-in plot on the shore bristled with the stalks of newly seeded marsh grasses planted by the New York City Parks Department.

Mr. Sanderson, who is a senior conservation ecologist at the Wildlife Conservation Society, gestured toward a tidal channel, above which loomed a four-story apartment complex with a “now leasing” sign.

“If we were here with the Lenape a few hundred years ago, they would be there in the channel in their dugout canoes,” he said. “But they would never have built their wigwam right there on the edge of the beach, because it’s dangerous. It floods, it’s exposed to the winds.”

The restoration area and the channel that abuts it sit incongruously between a busy avenue and a neighborhood of mostly new low-rise apartment buildings and multistory homes, many of which flooded during Sandy. The odd architectural mix and wild natural features make Rockaway unique. They also present unique challenges to city planners.

The city today has lost most of its protective sand dunes and close to 80 percent of the coastal marshlands that it had historically. Without these natural barriers, residents in the Jamaica Bay area are far more vulnerable to rising waters.

In a multimillion-dollar effort to remedy the situation, state and city agencies and the National Park Service are partnering with nonprofit groups to build “living shorelines” — restored coastal edges that are stabilized with sand, rocks and bags of oyster shells, as well as deep-rooted native plants. Roughly 10,000 acres of parkland ring Jamaica Bay and the Rockaway Peninsula.

Marit Larson, who is leading the restoration work for the city, said that the purpose of the dozens of projects that are underway on public land throughout Jamaica Bay is threefold: helping nature to recover, providing a buffer for residents against coastal storms and also offering New Yorkers natural sanctuaries where they can go to renew themselves.

Residents are mostly enthusiastic about the efforts to strengthen shorelines and create ecological buffer zones.

But nobody suggests that Jamaica Bay can be restored to its condition before urbanization.

In the 19th century, the city’s fishermen flocked there by horse and buggy. “Their boats were so thick on a Sunday, you could practically walk from one to the other without getting wet,” according to John R. Waldman, a biology professor at Queens College who wrote a book with Mr. Sanderson about Jamaica Bay.

Nowadays the fishers are fewer, but the fish are making a surprising comeback, said Mr. Waldman, who recalls spending many happy hours chasing striped bass in the autumn as the ravenous fish jumped all over the deeper channels. The bass, along with Southern species like skilletfish, are prevalent in the bay as some cold-water fish (like tomcod and winter flounder) become scarcer as waters heat up.

Seals are even returning to the islands, and whales not infrequently venture into the deeper channels. Diamondback terrapins, hunted almost to extinction during the colonial era for turtle soup, currently number around 10,000. New oyster reefs are being seeded.

“The future is looking good,” Mr. Waldman said. “Jamaica Bay is relatively unpolluted and still functioning fairly well in an ecological sense.” This, he says, is owed largely to the aggressive protection efforts undertaken by public and private agencies.

While the natural environment continues its surprising comeback in Jamaica Bay, time may be running out for the people who live there.

After Hurricane Sandy, a debate ensued about how to prevent the next catastrophe. On the one hand were the technological solutions like the one proposed by the Army Corps of Engineers: a massive sea wall from Sandy Hook, N.J., to the Rockaway Peninsula. In addition to its huge expense, critics of the project said that it would protect only against storm surges but not sea level rise itself, which poses the more enduring threat. Others maintained that a greener approach — restoring natural features like sand dunes, oyster reefs and coastal wetlands — offered the strongest defense.

In the end, the more moderate measures prevailed. Shorelines are being “hardened” in some locations with concrete walls and rock jetties; in other places natural coastal ecosystems are being rebuilt. The proposal for a giant sea wall has been withdrawn for now but will surely be reconsidered if another Sandy-size storm hits the metropolitan area.

Given the projections that the sea level may rise six feet or more along U.S. coastlines before the end of the century, most experts say the government will eventually have to buy out homeowners in the lowest-lying areas and help move them to higher ground. Ultimately, many of the people who live around Jamaica Bay are going to have to leave.

“A conversation needs to happen at the neighborhood level, and the city should take the lead,” said Robert Freudenberg, a vice president of Regional Plan Association, an urban policy group that works in partnership with local governments in the New York metropolitan region to promote sustainable development. “We have to start preparing residents for maybe being the final generation in those places. But that is the conversation that nobody wants to have.”

Donovan Finn, a professor of environmental design at Stony Brook University and a member of the Science and Resilience Institute at Jamaica Bay, agrees that there are only tough choices ahead.

“The question is which is the less difficult option,” he said. “This huge engineering sea wall project that’s going to cost tens of billions of dollars and will have big ecological and other impacts, or uprooting 50,000 or 100,000 families from their homes,” Mr. Finn said. “I think it’s an open question. Neither one is easy. None of this is easy.”

Mr. Finn added that a sea wall, even if built, would offer only a temporary fix since sea levels would eventually rise to supersede it. Ultimately in coastal areas throughout the city, he says, we’ll need to combine “green infrastructure” like living shorelines with “gray infrastructure” like the system of smaller sea walls and levies used in the Netherlands, much of which lies below sea level.

But the city needs to act quickly, Mr. Finn said. A number of neighborhoods in Jamaica Bay are already experiencing “sunny day flooding,” which happens during the highest tides every month.

By far the most ambitious — and widely admired — project aimed at minimizing flooding risks is being conducted by the Army Corps of Engineers. This is not the gargantuan sea wall originally proposed but a humbler effort, which is enlarging several barrier islands in Jamaica Bay, and even creating some new ones.

“We have already restored more than 160 acres,” Lisa Baron, a project manager with the corps, said. “We plan on restoring another 206 acres on five islands.” Some of the most enthusiastic proponents of the new islands are the people of Broad Channel, who can see them rising out of the bay.

Broad Channel looks more like a New England fishing village than a big-city neighborhood, and it remains somewhat insular, with many families who have lived there now for several generations. Residents tend to be politically conservative but environmentally active. They are currently leading the charge to save their beloved bay.

One of the main proponents is Daniel Mundy, a 58-year-old battalion chief in the New York Fire Department.

Mr. Mundy grew up in Broad Channel and has a long history of organizing residents to help protect the bay. His love affair with the water started early. While other city kids headed off to ball fields after school, a young Dan Mundy would paddle his kayak through the labyrinth of creeks and channels in Jamaica Bay. “You had the place to yourself,” he recalled. “It did not seem like you were in the city at all.”

During the 1990s, however, Mr. Mundy noticed a change. “The salt marshes were just melting away, becoming lifeless mud flats,” he said. “We also saw that the water had become rust-colored. We were seeing fish die off, small bait fish piling up dead on the shore.”

At that time, Mr. Mundy showed up with a handful of neighbors at meetings held by agencies charged with protecting the environment. “We were told: ‘It’s just not happening. Listen, you guys mean well. But you’re not scientists — you’re a fireman, you’re an electrician,’” Mr. Mundy said.

Then the New York State Department of Environmental Conservation decided to conduct its own analysis. It found that the bay was indeed losing upward of 50 acres of wetlands a year to erosion. And high nitrogen levels caused by effluent from four sewage treatment plants were killing off fish and other creatures.

It was the confirmation residents needed. Mr. Mundy organized the Jamaica Bay Ecowatchers, which joined forces with the Natural Resources Defense Council and went to court to stop the pollution that was destroying the salt marshes. In 2010, they worked out a negotiated settlement with the Bloomberg administration.

“We won a hundred-million-dollar agreement that forced them to upgrade all the treatment plants,” Mr. Mundy said. “It’s had an amazing impact; the water is now the clearest we’ve ever seen. We also received $15 million to create new wetland islands.”

He added: “Those waves that formed during Sandy were huge. If you place new wetland islands out there, that storm energy gets dissipated. It’s still going to come into my house, but the wave energy will be blunted. My house won’t get knocked down or washed away.”

Recently, the Ecowatchers were instrumental in blocking a proposed new runway at Kennedy International Airport, which the group said would have destroyed hundreds of acres of bay and salt marsh.

Local champions like Mr. Mundy and Mr. Riepe have succeeded in making Jamaica Bay something of an ideal for ecological recovery in a major urban area. But the question remains: How much longer can the residents of Broad Channel stay there?

On a recent bird-watching tour that he led in the Jamaica Bay Wildlife Refuge, Mr. Riepe pointed toward an osprey nest on top of a wooden pole that he and his volunteers had just set up. “I’ve been involved with efforts to bring back raptors for the past 30 years,” he said. “We’re restoring habitats. But sea level rise is opposing our restoration efforts.

“I don’t think the marshes that we have will be all that protective if we have a major storm,” Mr. Riepe continued. “So that’s our goal for the future: to greatly increase the scope of the restoration effort to rebuild the marshes and put in new islands.”

But he is frustrated by the slow pace of the work. “Congress has to allot funds to the Army Corps of Engineers,” he said. “They have to get a contractor, they have to find clean fill. In the meantime, nature is relentless. Nature doesn’t take a holiday. Nature doesn’t have a Congress to deal with.”

He paused for a moment to reflect. “It’s a beautiful place to live,” Mr. Riepe observed somewhat wistfully. “But nothing is forever.”