Are beavers good for streams? Dam straight they are. Very, very good. Don’t take my word for it. Check out this excellent new paper from the Methow Project.
Reintroduced Beavers Rapidly Influence the Storage and Biogeochemistry of Sediments in Headwater Streams (Methow River, Washington)
North American beavers (Castor canadensis) were targeted within North American headwater landscapes by European loggers and fur traders in the 19th century, reducing beaver populations to near extinction by 1900. The extirpation of beavers from river networks has had profound effects on riparian zones, including channel geomorphology, temperature regimes, sediment storage, channel-floodplain connectivity, carbon storage and nutrient dynamics. i
Consequently, reintroducing beavers has been provisionally implemented as a restoration approach within some watersheds. We characterized how reintroduced beavers influence the short-term dynamics of organic material accumulation within the sediments of 1st and 2nd order streams within the Methow River watershed of Washington State. In collaboration with the Methow Beaver Project, we identified four creeks where they had reintroduced beavers within the past five years, as well as a control non-beaver pond. At each site, we collected shallow sediment cores from upstream, downstream, and within beaver ponds, and then measured organic material via elemental analyses of sediment carbon (%C) and nitrogen (%N) content. We compared those samples to sediments accumulated in local pond areas not created by beaver activity.
Our results show greater organic C and N content of sediments in beaver ponds than non-beaver ponds. C/N ratios indicate elevated accumulation of allochthonous organic material in beaver impoundment sediments that would otherwise not be integrated into headwater streams from the terrestrial landscape. These findings suggest that the reintroduction of beavers could be an effective means to promote restoration of whole ecosystem function.
Kena Fox-Dobbs, associate professor of geology and environmental policy and decision making, and Peter Wimberger, professor of biology, have spent years working with the central Washington organization that aims to relocate beavers from agricultural areas and farmland to wilderness streams. They’ve been studying how these remote areas—not recently exposed to beaver activity—change with the introduction of the large rodents. This summer, their research has expanded to examine whether beavers speed the recovery of areas burned by wildfires.
As nature’s engineers these amazing animals build dams that keep waterways healthy and create ponds and wetlands that provide important habitat for young fish and other animals, protecting them and allowing them to grow.
