For decades, federal protections were extended to wetlands adjacent to “waters of the US” by the Clean Water Act. In its Sackett v. EPA ruling, however, the US Supreme Court redefined the meaning of “adjacent,” eliminating protections to wetlands without a continuous surface connection to these waters (i.e., geographically isolated wetlands, GIWs). Yet it remains unclear how this continuous surface test will work in reality, where ecological connectivity often extends beyond physical connectivity. Here, we calculate the number of US wetlands that could be considered geographically isolated depending upon the distance threshold used to define isolation (ranging from 1 m to 100 m from the nearest hydrological feature). Overall, we estimate that 27–45% of wetlands, at minimum, could be considered geographically isolated using this range of distance thresholds. Over 3 million wetlands are within 1–100 m of the nearest hydrological feature, making them most vulnerable to losing prior protections from the Clean Water Act. The Midwest and Northeast have the largest share of potential GIWs within this range. Freshwater emergent wetlands and forested/shrub wetlands make up the majority of these vulnerable wetlands, though this varies by state. Roughly 47% of these wetlands are located in states without state-level protections for GIWs. Our analysis highlights the heterogeneity of risk to wetlands across the country and the scale of the uncertainty imposed by the updated Sackett definition. State-level protections that are robust to changes in federal protections are urgently needed to secure the country’s wetlands from further pollution and destruction.

几十年来，《清洁水法》将联邦保护范围扩大到“美国水域”附近的湿地。然而，在Sackett 诉 EPA案的裁决中，美国最高法院重新定义了“相邻”的含义，取消了对与这些水域没有连续表面连接的湿地（即地理上孤立的湿地，GIW）的保护。然而，目前尚不清楚这种连续的表面测试将如何在现实中发挥作用，因为生态连通性往往超出了物理连通性。在这里，我们根据用于定义隔离的距离阈值（距离最近的水文特征从 1 m 到 100 m）计算可被视为地理隔离的美国湿地数量。总体而言，我们估计，使用此距离阈值范围，至少 27-45% 的湿地可以被视为地理上孤立的。超过 300 万个湿地距离最近的水文特征在 1-100 m 范围内，这使得它们最容易失去《清洁水法》先前的保护。在此范围内，中西部和东北部的潜在地理信息武器所占比例最大。淡水新兴湿地和森林/灌木湿地构成了这些脆弱湿地的大部分，尽管各州情况有所不同。这些湿地中大约 47% 位于没有国家级 GIW 保护的州。我们的分析强调了全国湿地风险的异质性以及更新的萨克特定义所带来的不确定性的规模。迫切需要能够应对联邦保护变化的州级保护，以确保该国的湿地免受进一步污染和破坏。