By Robin Meadows
Staten Island lies in the heart of California’s Sacramento-San Joaquin River Delta, and exemplifies the woes of this troubled region. More than one quarter of the Delta―about 200,000 acres―is deeply subsided. This extreme soil loss puts stress on the levees encircling the islands. And, because the soil there is peat and so rich in organic matter, subsidence in the central Delta also spews carbon into the air.
“It’s like a chimney of greenhouse gases,” says Sydney Chamberlin, project director for Climate & Nature-based Solutions at The Nature Conservancy, which bought Staten Island in 2001. “The Delta is on an unsustainable trajectory if we continue business as usual.”
Staten Island has lost so much soil over the last century that its northern end is about 10 feet below sea level. Its southern end is even deeper. “The water is high on one side of the levee and then you look on the other side and it’s about 25 feet down,” Chamberlin says. “It’s mind-boggling.”
But Staten Island also offers among the best hope for solving the Delta’s soil loss and greenhouse gas emission problems. The Nature Conservancy is testing ways of halting and even reversing subsidence on the island, and the latest project is a wetland restoration slated to begin as early as this summer.
Benefits of reversing subsidence extend far beyond the Delta. Wetland restoration in the region is among the goals for statewide nature-based climate solutions. And more resilient levees would lessen the risk of breaches―which can draw in salty water from the San Francisco Bay―and so help protect much of the state’s water supply. Delta exports irrigate millions of acres of farmland and deliver drinking water to two-thirds of Californians.
UNPARALLELED CARBON STORAGE
Peat consists of partly decayed wetland plants, and stores more carbon than all other types of soil and vegetation globally including forests. “Wetlands are the best carbon sequestration system in the world,” says Lisamarie Windham-Myers, Delta Lead Scientist for the Delta Stewardship Council.
Wetlands built up deep peat soil in the Delta over thousands of years, until settlers began draining the area for agriculture in the mid-1800s. When peat is exposed to air, microbes finish breaking down or oxidizing the plant material, releasing carbon dioxide. “The peat just blows off,” Windham-Myers says.
Half of the Delta’s peat is now gone, and losses are ongoing. The Delta is subsiding at up to 1.5 inches per year, giving off more than 1.5 million tons of greenhouse gases annually.
“This soil carbon is so valuable,” Windham-Myers says. “It’s as if we have a big pool of gasoline and we’re letting it volatilize.”
REBUILDING PEAT
Stopping subsidence―and carbon emissions―in the Delta is as simple as getting peat soil wet again to keep microbes from oxidizing it. Reversing subsidence is more involved, and entails both rewetting soil and rebuilding peat. The Nature Conservancy is evaluating options for cutting carbon emissions and reversing subsidence on Staten Island.
More than 4,000 acres of Staten Island have already been converted from corn to rice fields. The latter can be flooded for much of the year to curb peat loss and so carbon emissions.
Now The Nature Conservancy is poised to restore wetlands on just over 1,000 acres in the southern tip of Staten Island. The two-phase project will start with about 400 acres that have been designed and permitted in partnership with Ducks Unlimited, a nonprofit dedicated to conserving waterbirds and their habitats. The cost of this first phase is about $7.6 million, and funders include the Sacramento-San Joaquin Delta Conservancy, a state agency and project partner, and the California Department of Fish and Wildlife.
The goals for Staten Island’s ambitious wetland restoration extend beyond carbon sequestration and subsidence reversal. Other priorities include ensuring high-quality wildlife habitat and agricultural opportunities as well as economic viability.
Ducks Unlimited project lead Aaron Will looks at it like this: “Here’s 1,000 acres, how do you balance all these needs?” The answer draws on his team’s experience restoring wetlands elsewhere in the Delta, including on Twitchell and Sherman islands.
For the first phase of the Staten Island wetland restoration, the team settled on a mix of semi-permanent wetlands, which are essentially permanent but can be drained if necessary; seasonal wetlands, which provide seeds that ducks eat; and rice fields, which provide leftover grain for sandhill cranes. About 15% of the Central Valley’s Greater Sandhill Cranes, which are state-listed as threatened, winter on Staten Island.
“This project is cool,” says Will, a biologist who has restored wetlands for two decades. “I really like it from the birds’ standpoint―there’s a diversity of habitats for a big variety of birds.”
Will describes the wetland design as a meandering mosaic of islands, potholes, shallow waters for cranes, and tule-lined channels for ducks. Water depths range from six inches, which many shorebirds favor for foraging, to 18 inches, which dabbling ducks favor.
The team also hopes to partner with tribes on which native species to replant in the new wetland. Ultimately, the Staten Island restoration may also offer tribes the opportunity to collect tules for cultural uses, such as making baskets and boats.
The wetland construction will likely begin this July or early in 2026 and, either way, be complete in 2027. Instruments will monitor greenhouse gases at the restoration, which is expected to reduce carbon emissions by nearly 4,000 tons per year.
ECONOMICS OF NATURE-BASED CLIMATE SOLUTIONS
California has recently begun to embrace nature-based solutions for climate change, setting targets that include restoring 60,000 acres of wetlands in the Delta region by 2050. A recent study found that nature-based climate solutions are cost-effective as well as often more effective than engineering climate solutions.
Most landowners in the Delta depend on agriculture for their livelihoods, making conversion to rice appealing as it is a high-value crop. But wetlands would take farmland out of production, making them a “tougher sell,” Chamberlin says.
The carbon market is one possibility for making agriculture-to-wetland conversions pencil out economically. The American Carbon Registry has now enrolled protocols for conversion to rice fields and wetlands in the Delta, allowing landowners who reduce emissions to sell credits that carbon producers can buy to offset their emissions.
Altogether, conversion to rice and wetlands is projected to reduce Staten Island’s carbon emissions by nearly 600,000 tons by mid-century. Wetlands make an outsized contribution to this reduction, accounting for just one-fifth of the land converted but one-quarter of the emissions decrease.
The hope is that voluntary carbon offset projects on Staten Island, and elsewhere in the Delta, will convince the state Air Resources Board to adopt the protocol under the Cap-and-Trade compliance market. This would double the value of the carbon credits, making the carbon market that much more of an incentive to farmers.
But Chamberlin also acknowledges that “there are a lot of uncertainties, questions and challenges to the carbon market.” So she and her team are also considering other possible incentives for farmers to restore wetlands in the Delta, such as decreasing flood risk and adapting to sea level rise.
The Staten Island team is also exploring how to streamline permitting, which can be time-consuming and costly, and how to secure more stable financial support for nature-based solutions like wetland restoration. Conversion from corn to wetlands runs about $10,500 per acre, and funding sources rarely cover the ongoing monitoring key to documenting that a project reduces carbon emissions.
“Staten Island is a living lab,” Chamberlin says. “We test different strategies to find solutions that others can implement.”
