New York City’s wetlands are facing a perilous future. Over the last 400 years, development, pollution, landfill and erosion destroyed 85 percent of the city’s salt marshes and 99 percent of its freshwater wetlands. Dozens of acres are lost every year across the five boroughs. Only 5,650 acres now remain, which would cover about a third of Manhattan.

A new report released Wednesday, called the Wetlands Management Framework for New York City, seeks to create a more stable future for these endangered ecosystems. Created by the Natural Areas Conservancy and the New York City Department of Parks & Recreation, this 30-year plan identifies more than 300 acres of wetland restoration projects—about the size of the Financial District—in NYC Parks properties. The proposal highlights the need for hundreds of millions of dollars in funding to preserve, restore and manage the region’s wetlands and streams.

The city’s waterfront is facing a critical moment. Sea levels are expected to begin rising at an accelerated rate, inundating the coast and drowning its salt marshes. In the next 30 years, the New York City Panel on Climate Change projects that the city will experience up to 2.5 feet of rising coastal waters.

A marsh migration to higher ground will soon become necessary, according to the report. The wetlands framework calls for this maneuver to occur in the city’s coastal parklands or in property acquired by local officials, including former residential neighborhoods that have retreated from the ocean. Several communities in New York City are currently undergoing a managed retreat from sea level rise, and hundreds of houses in Staten Island have already been demolished and replaced by wetlands as part of a New York state buyout program.

“Everything we have left is critically important because everything we have left is just a tiny fraction of the historic biodiversity that we had in our city,” said Sarah Charlop-Powers, the executive director of the Natural Areas Conservancy and one of the report’s authors. “There is an urgency, due to wetland loss and habitat loss and sea level rise, to not sit on this plan for a decade, but to begin to move on implementing these recommendations in the short term.”

A salt marsh in the Fresh Creek Nature Preserve

The wetlands framework was written by seven authors from the conservancy and NYC Parks, based on countless hours of research and fieldwork. The report’s foundation relies upon a 4-year study that assessed the conditions of 1,300 acres of wetlands and 26 miles of streams located in public parks. This study found that the city’s freshwater wetlands were in relatively good health, while its most extensive salt marshes exhibited moderate-to-poor health.

“We’ve been working on this report for decades, to be honest,” said Jennifer Greenfeld, the Assistant Commissioner for Forestry, Horticulture and Natural Resources at NYC Parks, who co-wrote the report. “The Parks Department has been in the business of wetlands protection and restoration, management and planning for over 30 years. So in one sense, this is partially a culmination and encapsulation of all that work.”

Revitalizing wetlands is not an easy or inexpensive process. It can cost between $1.5 million to $2 million to restore just one acre of marshland. But according to the new analysis, these ecosystems are vital habitats for more than 325 species of birds, 315 species of plants and 200 species of fish and shellfish. Coastal marshlands also provide a crucial buffer from storm surges, reducing the impact of waves and flooding. Greenfeld says the team’s findings serve as a “shovel-ready menu” for building future wetlands.

“Regardless of the uncertainties of the future, we do know that what we have is worth saving,” said Greenfeld. “We are ready when the money comes. We know what should happen. We have a design for some of these. We have already started to talk about permitting for others.”

Fresh Creek, an inlet on the north side of Jamaica Bay.

The complexities of wetlands restoration reveal themselves along the shoreline of Jamaica Bay. This 18,000-acre estuary is bigger than Manhattan and home to hundreds of species of birds and fish—and dozens of residential neighborhoods. Several rehabilitation projects are underway here, including a one-acre expansion of salt marsh on Fresh Creek, an inlet on the north side of the bay. During a recent visit to the creek, Charlop-Powers, Greenfeld and a third author, Marit Larson, discussed the challenges of working with marshlands in an urban environment.

As they walked across a small section of recently excavated landfill, yellow-crowned night herons hunted for crustaceans nearby. Marsh grasses will be planted by hand here in the coming weeks, but the tidewaters are already flowing into the site. A web of netting made from jute protected a fresh layer of sand from erosion. Across the street, rows of houses looked over the inlet from the roads of Canarsie, which were flooded during Hurricane Sandy. A study published Tuesday estimates that climate change increased damages from this 2012 storm by $8 billion.

Crossing this nascent landscape illustrated the tangled intersections of bureaucracy, pollution and nature that NYC Parks must navigate as it seeks to restore wetlands. The new salt marsh under development here aims to mitigate the impacts of a sewage project in the neighborhood, where the Department of Environmental Protection replaced a different section of marshland with a stormwater outfall pipe. It will take years of work and millions of dollars to transform this one acre of landfill back into a healthy salt marsh habitat.

“This is the smallest size of project that it makes sense to do,” said Marit Larson, the Chief of Natural Resources at the Parks Department, looking out over the Fresh Creek site. “We do have a much longer list of projects that we have identified.”

As part of the framework, NYC Parks has created a detailed geospatial database of potential initiatives across the city and their costs. One of those proposed projects is a 4-acre restoration along Fresh Creek, which would be done in conjunction with a larger U.S. Army Corps of Engineers rehabilitation plan.

Three authors of the wetlands report, visiting a restoration on Fresh Creek.

The wetlands framework identifies a total of 328 acres of salt marsh and freshwater wetlands that could be restored in NYC Parks properties across the city, at an estimated cost of $472 million. The report also highlights 19 priority projects for immediate action. These range in size from a 4,356-square-foot salt marsh restoration on Broad Channel Island in Jamaica Bay to a 6-acre expansion of the wetlands at Alley Pond Park in northern Queens.

These priority projects would restore 45 acres of wetlands and daylight Tibbet’s Brook in the Bronx, at an estimated cost of $160 million. Some have already been planned out and are readying to break ground, while others may take a decade or more to complete.

“We think all of these projects should happen,” said Larson. “They would all create a more vibrant city. They will help restore wetlands and increase function. And we don’t want any one of them to be forgotten.”

An abandoned boat on Fresh Creek.

As sea level rise accelerates, New York City’s saltwater wetlands will either migrate to higher ground or perish. With sea levels projected to rise up to 9.5 feet in the next 80 years, the pace of this destruction will quicken, potentially drowning thousands of acres of marshland.

Along the shores of Jamaica Bay, the city has acquired and demolished several homes in Ramblersville, a neighborhood in Howard Beach that Hurricane Sandy badly damaged. NYC Parks will take ownership of these properties this year, according to the report, and either return them to wetlands or preserve them for a future marsh migration. A five-acre, $4.8 million restoration project in Ramblersville is one of the report’s priority projects.

Homes in Canarsie, Brooklyn overlook the Fresh Creek Nature Preserve.

Although NYC Parks is currently working at a smaller scale, thousands of acres would be needed if the city were to facilitate a full-scale salt marsh migration. Whether this land is acquired from residents fleeing from climate change or from parks going underwater, it will take an enormous effort to reshape the city’s new coastlines into a healthy ecosystem—and not just a collection of flooded forests and abandoned streets.

“Climate change is the existential crisis of our lifetimes, and we have an opportunity to address it in a way that celebrates the city we have and builds a city that looks at equity and resilience in a positive way,” said Charlop-Powers. “Let’s protect and care for everything that we currently have, and let’s think about where we can add to that portfolio in anticipation of things like sea level rise.”