How wet must a wetland be to have federal protections in post-Sackett US?

In 2023, the US Supreme Court’s majority ruled in Sackett v. Environmental Protection Agency that only wetlands that are “indistinguishable” from federally protected waters “due to a continuous surface connection” are federally protected. This study estimates the potential impact of interpretations of the ruling on federal wetlands protections, using a qualitative measure of wetland “wetness” as a proxy for the new requirement. An estimated area ranging from ~17 million acres (19%) to nearly all 90 million acres of nontidal wetlands in the conterminous United States could be without federal protections, and variability in state protections creates hotspots of risk. The high-level estimates provided here represent a first step toward understanding the long-term impacts of Sackett v. Environmental Protection Agency on federal wetlands protections and highlight the uncertainty introduced by the ruling.

Methods
This dataset represents estimated federal jurisdictional status of wetlands for the conterminuous US using different potential interpretations of the Supreme Court's majority opinion in Sackett v. EPA. For the full methodology, refer to the linked preprint's "methods" section.

These data were produced using the National Wetlands Inventory (NWI), National Hydrography Dataset Plus High Resolution (NHDPlus HR), NWI Difference Product line, and the PAD-US dataset. Wetland polygons from the NWI were filtered to better align with the US Army Corps of Engineer's 3-factor definition of wetlands and intersected with select buffered NHDPlus HR features. Wetland "wetness", derived from the NWI's Coward Code Water Regime modifier, was used as a proxy for different interpretations of a "continuous surface connection", such that spatially contiguous wetland polygons that met or exceeded a specific "wetness" were estimated as jurisdictional if any polygon in a group was estimated jurisdictional. NWI polygons with an NWI difference product impervious surface percentage of 5% or greater were excluded.