Dam good! Beavers may restore imperiled streams, fish population
Utah State University scientists report a watershed-scale experiment in highly degraded streams within Oregon’s John Day Basin demonstrates building beaver dam analogs allows beavers to increase their dam building activities, which benefits a threatened population of steelhead trout.
Bouwes is lead author of a paper published July 4, 2016, in the journal Nature’s online, open access Scientific Reports that details the seven-year experiment conducted in streams within north central Oregon’s Bridge Creek Watershed. Contributing authors are Bouwes’ USU colleagues Carl Saunders and Joe Wheaton, along with Nicholas Weber of Eco Logical Research, Chris Jordan and Michael Pollock of NOAA’s Northwest Fisheries Science Center in Seattle, Ian Tattam of the Oregon Department of Fish and Wildlife and Carol Volk of Washington’s South Fork Research, Inc.
When Lewis and Clark made their way through the Pacific Northwest in the early 19th century, the area’s streams teemed with steelhead and beaver. But subsequent human activities, including harvesting beaver to near extirpation, led to widespread degradation of fish habitat.
Bouwes says these activities may have also exacerbated stream channel incision, meaning a rapid down-cutting of stream beds, which disconnects a channel from its floodplain and near-stream vegetation from the water table. He notes beavers build dams in the incised trenches, but because of the lack of large, woody material, their dams typically fail within a year.
“Our goal was to encourage beaver to build on stable structures that would increase dam life spans, capture sediment, raise the stream and reconnect the stream to its floodplain,” Bouwes says. “We expected this would result in both an increase in near-stream vegetation and better fish habitat.”
What really impressed us was how quickly the stream bed built up behind the dams and how water was spilling onto the floodplain, Bouwes says.
The researchers also documented increases in fish habitat quantity and quality in their study watershed relative to the watershed that received no BDAs and saw little increase in beaver activity. The changes in habitat in the watershed receiving BDAs resulted in a significant uptick in juvenile steelhead numbers, survival and production.
Go read the original research here. Maybe I have a simple mind but this graph makes me very happy. 
Many beaver fans have been talking about this for over a decade, but it took until 2016 for this work to be published at the watershed level, showing large scale advantages. If you want to know how long this has been in the oven, here’s a reminder.
This film was made in 2010, so you know the work was started before that. It takes a long time to document the effects that beavers have in creeks. Fortunately for us, this work just keeps attracting more and younger minds along the way, which means it can continue however long it takes to finally convince folk that beavers are good news for fish.
Oh and I received my beaver festival hat yesterday, so I’m all ready.
