Monday, October 28, 2013

In Defense of Beavers --Guest Post--

    When I lived in Wisconsin's North Woods, my favorite walk was a path that skirted the shore of one of the area's many kettle lakes. I walked it in all kinds of weather, at all times of year, and saw all sorts of interesting things as a result. One of my favorite memories of that lake is the time I got to observe a beaver hard at work doing beaver things: the sound of bubbling and splashing alerted me to its presence, and as I watched, it submerged repeatedly to work on dismantling a fallen birch tree. Each time it stuck its head underwater, butt and tail waggling on the surface, I would hear a distinct gnawing sound. Finally it was able to tow a limb to shore. 

Steve, Wikimedia
    I like beavers. Not everyone does, and I understand why – if you depend on the land for your livelihood, and a beaver moves in and floods your pasture or woodlot, that's a serious problem. Trees may drown, wildlife and livestock may be displaced, and it's easy to see how the immediate effects of beaver activity can be considered negative. However, across broader scales of time and space, beavers actually provide great benefits to both ecosystems and people:

    Beavers are good for biodiversity. At another place in Wisconsin where I used to go hiking, an old beaver wetland had matured into a broad, open meadow through which a stream meandered. (The beavers themselves and their dam had been removed some time before, but the surrounding trees had yet to recolonize the spot.) On a property that was otherwise heavily wooded, this was the best place to look for Sandhill Cranes, displaying American Woodcocks, and other species that require open ground. Studies have backed up the idea that beaver wetlands become local diversity hotspots, increasing the abundance and diversity of frogs, songbirds, and other creatures. 

    Beavers are good for water quality. Wetlands act as natural water filters, and beaver dams increase this effect, trapping silt and other material and reducing the amount of pollutants such as nitrogen and phosphorous from fertilizer that are washed downstream.

Fungus Guy, Wikimedia
    Beavers are good for flood control. Like manmade dams, beaver dams store water during high flows and release it gradually, reducing the severity of floods. This increased water storage also helps recharge aquifers and raise the local water table.

    Beavers are good for seafood. Since observing that beaver at work in a Northwoods lake, I've left Wisconsin and moved across the country to eastern Oregon. Beavers are important here, too, for a reason I wouldn't have expected: they're good for salmon. The Columbia River and its tributaries are famous for their salmon runs, and beaver dams create important rearing habitat where the newly-hatched fish can grow and mature before they make their return to the ocean. Restoring beavers (which have declined in the region due to “harvesting” by humans) is one of the priorities of the Oregon Department of Fish and Wildlife's Mid-Columbia Steelhead Recovery Plan. 

D. Gordon E. Robertson; Wikimedia
    Beavers are even helping the fight against climate change. Over the summer beavers briefly made science and conservation headlines with the release of a study showing that the wetlands they create actually sequester carbon. A researcher compared the amount of organic carbon stored in sediment in active beaver wetlands in Rocky Mountain National Park versus those that had been abandoned, and found that beaver activity significantly increased carbon sequestration. When beavers are removed and their wet meadows dry out, carbon storage declines. 

    When I was researching this post, one of the comments on an article I read claimed that “the beaver is a destructive animal that needs to be hunted or exterminated.” I've met people that share that view, but the truth (as it usually is) is more complicated. Despite the damage they can do, I hope that landowners are able recognize the potential benefits of beavers and continue to seek ways to coexist with them. If nothing else, we should be able to empathize with a creature that so drastically alters its habitat to suit its needs. After all, only one other animal is capable of similar feats: us. 

Rebecca Deatsman is an environmental educator based out of rural eastern Oregon. She writes about conservation and natural history on her blog, Rebecca in the Woods, and is also on Twitter as @rdeatsman.

Want to Learn More? Check Out These Scientific Articles:

E. Wohl (2013). Landscape-scale carbon storage associated with beaver dams
Geophysical Research Letters, 40 (14) DOI: 10.1002/grl.50710

H.A. Cooke, & S. Zack (2008). Influence of beaver dam density on riparian areas and riparian birds in shrubsteppe of Wyoming Western North American Naturalist, 68 (3), 365-373 DOI: 10.3398/1527-0904(2008)68[365:IOBDDO]2.0.CO;2

C.E. Stevens, C.A. Paszkowski, & A. L. Foote (2007). Beaver (Castor canadensis) as a surrogate species
for conserving anuran amphibians on boreal streams in Alberta, Canada Biological Conservation, 134, 1-13 DOI: 10.1016/j.biocon.2006.07.017

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