This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: By evaluating the health of waterways across the U.S., researchers have identified a network encompassing about one-third of rivers and streams that, if conserved and restored, could sustain the nation's freshwater biodiversity in the face of habitat degradation and climate change. Mark Anderson of The Nature Conservancy, U.S., led the new study, published Sept. 16, 2026, in the journal PLOS One.
During the past century, streams and lakes in the U.S. have deteriorated as more than 150,000 dams have fragmented river networks, and changes to the landscape and groundwater use have altered how and where the water flows. Many freshwater species are now in rapid decline, exacerbated by the impacts of climate change. To address this crisis, The Nature Conservancy worked with 66 freshwater conservationists to map freshwater networks in the contiguous U.S. and evaluate their resilience to degradation.
Each watershed was scored based on its connectivity, condition, water availability and naturalness of flow, and checked against local surveys of freshwater biodiversity. They put together a patchwork of rivers and streams—named the Freshwater Resilient and Connected Network—that covers 35% of the lower 48 states but could preserve freshwater biodiversity. Conserving this network will be challenging, however, as currently only 6% of the area is both protected and resilient, and 14% needs both protection and restoration.
The analysis also showed that, of the 5.2 million miles (8.4 million kilometers) of rivers and streams in the contiguous U.S., 33% rated as above average for resilience. While rivers that are above average should continue to support similar patterns of biodiversity in the future, those just above average may still require restoration. These networks are concentrated along the Pacific Coast; in the Northern Rocky Mountains; in Great Lakes areas of Wisconsin and Minnesota; in northern Maine; and in coastal regions along the southeastern U.S. and the Gulf of Mexico.
Vulnerable or below-average river networks made up 15% of those miles and were concentrated in the Southwest deserts, lower New England, the shortgrass prairie east of the Rocky Mountains and the agricultural lands of Midwestern states. The study provides a solid foundation for conservation efforts to sustain biodiversity in freshwater systems and a clear picture of the challenges ahead. Researchers said the analysis has already been used to identify dams for removal, prioritize land protection in key headwaters and improve conditions in river systems that need restoration.
The team acknowledges that the maps do not take into account human needs, but data representing human dimensions could be combined with this analysis to identify them. The authors add, "Resilience to climate change adds important context to our efforts to conserve freshwater biodiversity. We hope our study will help our state, federal, Tribal and other conservation partners make investments where they have the greatest chance to succeed into the future." A freshwater resilient and connected network to sustain biodiversity under a changing climate, PLOS One (2026).
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