Biodiversity Values of Geographically Isolated Wetlands in the United States

About This Project

NatureServe and our Network partners completed scientific assessments of the potential impacts on biodiversity of the court's decision to provide guidance to the federal agencies, states, tribes and local governments with responsibility for protecting these valuable habitats.

We used a nationally standardized classification of wetland ecological systems to identify geographically isolated wetland types in the US. Through review of scientific literature, input from regional experts, and compilation of existing location data for at-risk species (those species considered rare, imperiled or critically imperiled using NatureServe's standard criteria) we identified the at-risk species and plant communities that are supported by isolated wetland types throughout the United States.

The study demonstrated that geographically isolated wetlands represent a considerable amount of the United States' ecological diversity and provide habitat for a considerable portion of the nation’s flora and fauna. Of the 276 types of wetland described for the United States, 81 (29 percent) are "geographically isolated." A total of 274 at-risk plant and animal species are supported by isolated wetlands, with more than one-third (35 percent) apparently restricted to these wetland types.  Significant loss of isolated wetland habitats could seriously affect opportunities for the survival and recovery of the many rare or endangered species that depend on them.

  • Searchable data on isolated wetlands and their at-risk species and communities are available on NatureServe Explorer.


As a result of a 2001 Supreme Court decision (Solid Waste Agency of Northern Cook County vs. U.S. Army Corps of Engineers, 2001), some wetlands and other waters that are considered "geographically isolated" from navigable waters may no longer fall under the jurisdiction of the Clean Water Act, and therefore may no longer be under federal protection from development. The objective of this study was to assess the impacts on biodiversity of the Supreme Court’s decision.


This study documents that isolated wetland ecological systems support high levels of biodiversity, including significant numbers of at-risk species and plant communities.

Unless there is a policy response that reframes the jurisdiction of isolated wetlands under the Clean Water Act, States, tribes and local governments will increasingly be in a position to decide the fate of those isolated wetlands that no longer are protected under the Clean Water Act. The information and analyses contained in this study are designed to assist policy-makers and land managers at federal, state, and local levels to better understand their biodiversity value and plan for their conservation.