New interpretations following the recent Sackett v. Environmental Protection Agency (EPA) United States Supreme Court ruling could strip federal protections from up to 90 million acres of U.S. nontidal wetlands – nearly all that exist in the coterminous US – according to a new study. The findings reveal the potential scope and impacts of the regulatory changes and highlight the uncertainty introduced by the ruling. Enacted in 1972, the Clean Water Act (CWA) aims to restore and protect the quality of U.S. waters and wetlands. These federally protected waters, known as "waters of the United States" (WOTUS), include navigable waters and their connected streams and wetlands. In May 2023, the U.S. Supreme Court's ruling in Sackett v. EPA redefined which waters are considered WOTUS under the CWA, limiting federal protections to wetlands that have a "continuous surface connection" with larger water bodies, making them "indistinguishable" from streams, rivers, or lakes. According to Adam Gold, this notably narrow interpretation excludes many wetlands that were once previously protected despite their widely understood ecological significance. Moreover, the court's ruling did not account for the estimated number of wetlands and ephemeral streams affected by the decision nor consider the environmental or economic consequences of this loss of protection. Using flood frequency as a quantitative measure of wetland "wetness," Gold evaluated the potential impact of varying interpretations of the Sackett ruling and to estimate how much of the U.S.'s nontidal wetlands might lose protection. According to the findings, in the conterminous U.S., the area of nontidal wetlands estimated to lose federal protection under the Sackett decision ranges from 17.3 million acres (19% of nontidal wetlands) to nearly all 90 million acres. The lower estimate applies to isolated wetlands without considering "dryness," while more restrictive interpretations, which exclude "drier" wetlands, predict much larger areas of unprotected wetlands. For example, if wetlands must be at least seasonally or semi-permanently flooded to remain protected, between 55 million acres (61%) and 81.9 million acres (91%) of wetlands could lose federal protections, with nearly all wetlands excluded if permanent flooding is required. Gold's analysis also considers state-level regulatory protections and public-land statuses, showing hotspots, particularly in the Southeast and Great Plains, where wetland protections are most vulnerable. In a Policy Forum, Dave Owen discusses the findings and those from several similar studies focused on the recent regulatory changes in greater detail.
For reporters interested in trends, a January 2024 study by Greenhill et al. used machine learning to predict the scope of regulatory protections under different past interpretations of WOTUS. Additionally, a June 2024 study by Brinkerhoff et al. shows that much of the flow in larger rivers across the U.S. stems from now unprotected ephemeral streams.
