New research finds only a small portion of the nation's rivers may be able to maintain today's diversity of fish and other aquatic wildlife as the climate warms.
The study, published in the scientific journal PLOS ONE, mapped waterways across the Lower 48 to identify places that could give species more options as temperatures and water conditions change.
Researchers identified a network covering roughly 35% of the contiguous U.S. that could help sustain freshwater biodiversity. That includes waterways already considered resilient and others that could benefit from restoring flows, improving habitat, or reconnecting rivers.
"So when we're talking about resilience, we're talking about what it is about an ecosystem that gives species options to move and to adapt as their environmental conditions are changing," said Mary Khoury, a freshwater ecologist with the Nature Conservancy and one of the study's authors.
For fish and other aquatic species, that can mean having connected waterways that allow them to move into cooler or more suitable habitats.
Khoury said longer-lasting snowpack and less nearby development can also make waterways more resilient.
Some Western waterways stand out. Mountain rivers in Idaho and Montana and headwaters of the Colorado River system are among the more resilient areas identified by researchers.
Desert rivers in New Mexico, Arizona, and southern Nevada are more vulnerable, where water is already scarce and a warming climate is putting additional pressure on freshwater ecosystems.
Water availability was especially important in the arid West. The researchers looked for waterways with features such as year-round flows and connections to groundwater.
Connectivity is another important factor. Dams and other barriers can leave fish with fewer options as warming water pushes them toward cooler or more suitable habitats.
"They are limited to what's wet, right?" Khoury said. "So, having more connectivity in the system gives them … more space, and also the potential to move into areas, especially if they're temperature-sensitive."
Researchers did not predict when individual rivers could lose biodiversity. Future precipitation is uncertain, and human activities — including water withdrawals, dam operations, and habitat restoration — can also shape what happens to waterways.
Instead, the new maps are meant to help conservationists and water managers identify where protection and restoration could make the biggest difference.
This story was produced by the Mountain West News Bureau, a collaboration between Boise State Public Radio, Wyoming Public Media, Nevada Public Radio, KUNR in Nevada, KUNC in Northern Colorado, KANW in New Mexico, Colorado Public Radio and KJZZ in Arizona as well as NPR, with support from affiliate newsrooms across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
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