Wednesday March 26, 2025
American Society for Microbiology —
To improve stream health and help restore wetlands, ecologists have increasingly looked to beavers for inspiration. Stream-spanning structures made of vegetation, called beaver dam analogues (BDAs), offer a cost-efficient way to slow down moving water. A new study suggests they have another benefit: improving water quality downstream.
This week in Applied and Environmental Microbiology, researchers report that BDAs significantly reduce the amount of a waterborne protozoal pathogen, Giardia duodenalis, in stream water flowing through a cattle ranch in California.
“We found that slowing down the water in these creeks allowed these pathogens, which can cause disease in animals or people, to be removed by the BDA structures,” said epidemiologist and senior author Woutrina Smith, DVM, MPVM, Ph.D., from the University of California, Davis. “The water that goes through the BDAs becomes cleaner.”
BDAs are built from natural materials, such as river plants woven through vertical wood posts in the stream. When these structures slow down a stream’s flow, water spreads out, increasing the interface between a floodplain and the stream. This can help restore degraded ecosystems, Smith said. Ecologists have been building these structures for more than 2 decades, and previous studies have shown that they can help shift riparian streams from a pulse of water released to slower long-term release of water throughout the year, as well as improving vegetation.