A peer-reviewed study published June 1 in the journal Nature Water quantifies the economic and social costs of wetland loss in the United States following the U.S. Supreme Court’s 2023 Sackett v. EPA decision, which narrowed Clean Water Act protections to only those wetlands with a continuous surface water connection to other waterbodies. The ruling stripped federal safeguards from millions of acres of wetlands that intermittently flood or connect to water systems underground.

Scientists from the University of North Carolina at Chapel Hill and the Environmental Defense Fund analyzed federal flood insurance claims data over 40 years and found that wetland destruction has increased those claims by $10 billion. The study estimates that unprotected wetlands provide $177 billion in flood-mitigation benefits nationwide, with North Carolina alone accounting for $4.6 billion of that value.

The researchers controlled for variables such as rainfall and the expansion of impervious surfaces like parking lots and rooftops. They found the highest increases in flood insurance claims occurred in the Houston metropolitan area, southeastern Louisiana, and coastal Florida. However, the study likely underestimates total losses because it examined only river and stream flooding, excluding coastal and tidal inundations, and because the National Flood Insurance Program covers only one-third of expected annual flood losses.

“What really stood out to me was the value of existing wetlands for flood risk reduction that may no longer have protections either at the state or federal levels,” said Adam Gold, senior manager for coasts and watersheds science at the Environmental Defense Fund. “That shows the recent rollbacks and federal wetlands protections under the Clean Water Act and at the state level have really potentially large impacts on downstream communities.”

Wetland loss and resulting flooding disproportionately affect communities of color and low-income neighborhoods, which are often situated in low-lying areas due to historic discriminatory zoning. Many residents in these areas cannot afford flood insurance. “While we know that wetland losses are occurring and have been increasing in recent years, it can be difficult to pinpoint the effects on the ground,” said Portia Osborne, executive director of the National Association of Wetland Managers. “To put a dollar amount on that benefit is especially important as those headwater wetlands are the ones most likely to have lost protection post-Sackett.”

Separately, the Carolina Wetlands Association will restore wetlands along Stony Run near Dunn, North Carolina. During Hurricane Matthew in 2016, a dam breach on Stony Run caused one death. “We’re trying to put them back into better shape so if flooding like that happens again the wetlands can take care of it,” said Rick Savage, the group’s executive director.