Waterbody connectivity: Linking science and policy for improved waterbody protection

Connectivity-the flows and exchanges of organisms, materials, and energy within and among watersheds-is a central paradigm in ecosystem science. Changes in those connections have consequences for ecosystem functioning and water quality downstream and upstream. Therefore, connectivity is a cornerstone for federal water protection under the United States Clean Water Act (CWA). In the present article, we review the science of connectivity, explain the history of changes in CWA jurisdiction defining waters of the United States, discuss implications for US water policy, and highlight key steps to align that policy with science. The Sackett v. EPA (2023) Supreme Court decision significantly reduced federal water protection for wetlands and headwaters, disregarding their connectivity with larger, protected waterbodies. To fulfill the goals of the CWA to restore and maintain the chemical, physical, and biological integrity of U.S. waters, Congress must amend the act, fully recognizing the multidimensional connectivity of aquatic ecosystems and ultimately incorporating these connections into ecosystem-level policy.