A Lifeline for New York’s Threatened Wetlands

Once a regular victim of illegal midnight dumping, Saw Mill Creek Marsh now provides habitat for three dozen species of birds, including the saltmarsh sparrow, whose population numbers are declining due to sea level rise encroaching on their breeding grounds. 

Surrounded by industry on Staten Island’s West Shore, the marsh is encircled by a chain link fence to stop local companies from damaging the wetland. Despite this, it is a healthy marsh, with tall grasses and winding channels—an impressive feature of the city’s most park-friendly borough. 

It is also New York City’s only wetland “mitigation bank.” The bank sells “mitigation credits” to developers who are planning to build on wetlands elsewhere in the city. This allows waterfront developers to comply with federal regulations.

Under Section 404 of the federal Clean Water Act, or the “No Net Loss” policy, a company or state agency building on a wetland must also restore it, or create a new wetland elsewhere, or buy “mitigation credits” as compensation. 

“In New York City, every project that is on the waterfront that impacts open water or a wetland requires that you create habitat elsewhere,” said Peg McBrien, vice president of ecological engineering at WSP, the firm hired to actually restore the marsh. “So even if you impact, say, a tenth of an acre of open water to fix a [sewage outflow] that’s on the harbor, you have to provide mitigation.”

In 2019, the New York City Economic Development Corporation, a quasi-public agency, funded the restoration of the Saw Mill Creek Marsh with the express intention of creating a wetland mitigation bank to produce those credits, thereby facilitating coastal development in other parts of the city. 

McBrien remembers her delight after dredging out old tires and contaminated soil and replacing them with tidal channels and clean sand. “What surprised me is just that there are really nice wetlands out there, too,” she said. “So we could expand that and end up having 54 acres of nice habitat.”

Without a wetland mitigation bank, the need to find sites on which to restore wetlands can delay a waterfront development, particularly in a city with such limited space. And, as large-scale post-Sandy coastal resiliency plans and renewable energy projects get underway, the competition for land can only increase, according to a November report by the Natural Areas Conservancy. 

Restoring the Saw Mill Creek Marsh as a mitigation bank was a complex undertaking. The efforts to get all the correct permits from federal regulators took five years. When WSP finally began the restoration, it had to hit multiple milestones to trigger the release of mitigation credits. 

In the end, the New York City Economic Development Corporation received a limited number of credits that it could then sell to developers building on wetlands around the city.  

Thus, the corporation essentially collects a delayed payment for restoring, and conserving, the marsh in Staten Island, which ensures that there is technically no loss of wetland in the area. Creating the mitigation bank, meanwhile, was considered an environmental win in its own right, given how the expansive marsh has proven to be a rich habitat for wildlife. 

“New York City is constrained in this mitigation realm because we don’t have the ability to have mitigation banks in the way a lot of other regions in the U.S. do, just because we’re dense and we’re highly developed,” said Emily Walker, the author of the Natural Areas Conservancy report. “A lot of sites that could potentially be, in theory, considered for a mitigation bank are so grossly contaminated from decades, if not hundreds of years, of industrial use, that this precludes them from being used as mitigation sites.”

Prior to the mitigation bank, a lot of compensatory restorations had been undertaken on an informal, as-needed basis by the city’s Parks Department, which has done restoration on public land funded by both private developers and city agencies. In these cases, the department sells mitigation credits to a developer before undertaking the restoration in a process called in-lieu fee. 

Once the wetland is rehabilitated, the Parks Department monitors the land long-term. 

But city land is a finite resource, and it is possible that, in a future with even more waterfront development, there could be increased competition for restoration sites. Rebecca Swadek, the director of wetland management for the city’s Parks Department, estimates that they have about 30 acres of property that is suitable for wetland restoration in this context. 

“We definitely have a limited amount of land and former wetland where we can do fill removal,” said Marit Larson, assistant commissioner of natural resources and planning at the city’s Parks Department. “That’s simply because we’re a finite city with boundaries.”

Another issue is that the “No Net Loss” policy only addresses wetland loss to development, which means the acreage lost to sea level rise often goes unacknowledged. 

“We manage about half of New York City’s 3,500 acres of salt marsh,” said Swadek. “There’s limited upland space to remove historical landfill and create new wetlands. But we do have around 1,500 acres of wetlands that are drowning under sea level rise that need care.”

Restoration ecologists like McBrien often plan for this eventuality by designing their restoration at higher elevations, or high marsh, so that the marsh is less likely to drown. She did this at Saw Mill Creek Marsh. 

In the city, Swadek and Larson would like developers to have the opportunity to fund not just the restoration of a wetland, but also the enhancement of an existing one. 

According to Walker’s report, this means that developers would have the option to fund thin sediment placement on top of an existing marsh to prevent drowning, or debris removal to improve the health of the marsh or even the acquisition of more inland space for marsh migration, as compensation for their waterfront projects. 

In the rest of New York State, these kinds of wetland restorations happen through a more formalized system. 

Besides a mitigation bank, which are more common across the state, developers can also pay mitigation credits through the in-lieu fee process. In contrast to the as-needed version in the city, nonprofits usually undertake these restorations rather than local agencies. These nonprofits are able to pool money together from different developers to restore more continuous wetlands, instead of undertaking individual restorations for each project. 

After approval from state and federal agencies, a larger wetland within the same watershed as the developments is restored and protected forever. Jim Curatolo founded one of the main nonprofits in the state that offers this service. 

“The [company] gets to go do their thing as soon as they get one piece of paper from us [proving] that we just sold them two credits, and we take on the responsibility of that impact,” said Curatolo. “We are now the ones held responsible to make sure the wetlands are built.”

Curatolo’s nonprofit, The Wetland Trust, buys former wetlands and then restores them at the developers’ expense. But from his perspective, he serves the wildlife commonly found in the state’s wetlands, and does what he can to prioritize them when looking at new sites on which to restore wetland. 

“I always like to say, that’s our clients—turtles, frogs and salamanders,” said Curatolo. “That’s who we work for. That’s who we have to make sure gets what they need.”

Curatolo is often excited by the number of species that return to the wetland after restoration. The larger the wetland, and the more it can sustain itself, the better the habitat it provides for Curatolo’s “clients.” He also often builds vernal pools, which are little ponds that only appear seasonally, to accommodate rare amphibians. 

“If you build a little vernal pool in the middle of the winter, and in May you walk there, I guarantee you it’ll have amphibian eggs in it, whether it’s small salamanders, toads, frogs—it’ll get used right away,” said Curatolo. “So that’s the exciting part. In a lot of these wetlands, as you restore them, that wildlife really comes back quick.”

Curatolo mostly works to restore freshwater wetlands, which are the most common outside of New York City and Long Island. Tidal wetlands are rare in other parts of the state, and the cost of development for them is very high. State and federal agencies are often more likely to deny a permit to build on one, particularly if it is healthy. 

“It’s really hard to find sites, and the expense is tremendous,” said Curatolo. “You wouldn’t want to impact them unless you really had to, for good reason, like for the good of the community.”

Though the Saw Mill Creek Marsh mitigation bank is considered a big win in a crowded urban environment like New York City, ecologists like Curatolo still prefer creating larger wetlands far from industry for compensatory restoration projects. 

“To me, as long as you’re in the same watershed, you should pick the site that’s sustainable and biologically most interesting, not something that’s closest to the impact,” said Curatolo. “We’re trying to figure out the best site for our clients.”

Ultimately, it takes decades for these restored wetlands to gain the ecological functions of the destroyed wetlands they are replacing. But New York City’s coastal communities also need protection from sea level rise and coastal storms. The future of wetlands may look different across the city, ecologists say, but these rich ecosystems will endure, as they do across the state, with the help of changing guidelines for their dedicated stewards.

“At the end of the day, do we want these spaces to require [compensatory] mitigation? In theory, no,” said Walker, referring to tidal wetlands. “But we also know that in a city as dense and complicated as New York, there are going to be those times where it is unavoidable. I think that’s why mitigation exists as a policy practice, for when you can’t reasonably avoid having the impact.”