Dr. Ellen Wohl.the accomplished fluvial geomorphologist and hydrologist didn’t go to graduate school to study beavers. She hasn’t spent her career sresearching them at Colorado State. Ellen studies rivers and knows more about them, their fluvial processes and history than maybe any human living.
But her research keeps bumping into one particular non-human over and over again,
The American Geophysical Union was formed in 1919 and is housed in Washington DC, (or was when I started this post- it may have been moved with the USDA by now to Kansas.) Their Centennial celebration invited scientists across the nation to show case important works in a field that is literally defining its own boundaries.
And one of those chosen scientists is Dr. Ellen Wohl, who wrote about our own forgotten impact on rivers and brought an old friend along to help her tell the story.
Forgotten Legacies: Understanding Human Influences on Rivers
Logging, urbanization, and dam building are a few ways people have significantly altered natural river ecosystems. Understanding that influence is a grand challenge of our time.
Rivers are fundamental landscape components that provide vital ecosystem services, including drinking water supplies, habitat, biodiversity, and attenuation of downstream fluxes of water, sediment, organic carbon, and nutrients. Extensive research has been devoted to quantifying and predicting river characteristics such as stream flow, sediment transport, and channel morphology and stability. However, scientists and society more broadly are often unaware of the long-standing effects of human activities on contemporary river ecosystems, particularly when those activities ceased long ago, and thus, the legacies of humans on rivers have been inadequately acknowledged and addressed
Her basic tenet? We have screwed up our rivers for so long that we don’t even remember what they’re supposed to look like. We need to look at historical clues to understand what we should be striving for in restoration. And you know what that means.
Legacies, in this context, are defined as persistent changes in natural systems resulting from human activities. Legacies that affect river ecosystems result from human alterations both outside river corridors, such as timber harvesting and urbanization, and within river corridors, including flow regulation, river engineering, and removal of large-wood debris and beaver dams.
The desecration we created was the result of no invasion. The damage was done by our own hands, for our own gain for hundreds of years. Centuries of trapping lead to centuries of broken river mechanisms, and if we’re going to fix that we need to strive to replace some semblance of what was stolen.
There are various approaches to accomplish this. One is to maintain or restore characteristics of a river corridor that create a desired process. This approach underlies, for example, the restoration of riparian vegetation as a buffer to retain upland inputs of nitrogen, phosphorus, and fine sediment. Another approach is to create a template of river corridor form that will facilitate desired processes. Examples include the emplacement of engineered logjams [Roni et al., 2014] or beaver dams [Bouwes et al., 2016] to mimic the function of natural features, setting back levees to restore channel-floodplain connectivity [Florsheim and Mount, 2002], and removing artificial barriers to allow high flows to return to abandoned channels [Nilsson et al., 2005b].
To fix our rivers bring back beavers. Don’t look at me, I didn’t say it. This is in a national publication striving for the health of our planet. I trust Dr. Woh’s judgment implicitly in these matters, don’t you?
Effectively addressing these questions requires that we understand how past human activities have modified river corridor process and form, as well as how those past alterations constrain river science and management going forward.
You have to know what was lost before you try and get it back. That seems obvious. And that means we have to recognize how much we devastated those streams by taking out beavers of them. Which means we have to admit that beavers are good for streams. It’s basic science. No one can argue with that?
Oh, wait. Never mind.
Speaking of government scientists I have a funny funny joke I’ve been saving to tell you.
Seems that all the new restrictions on beaver trapping for the USDA in Oregon and California have made wildlife services want to add some new tools to the rusty box. They are reportedly working on a brochure to give to landowners when they complain about beavers that talks about coexistence and all the good things they do. So of course they’re looking for photos and approached Michael Pollock to see if he had some.
So of course he asked me. If Worth A Dam might have a few good beaver photos worth sharing with wildlife services to teach folks to live with beavers.
Now that’s one place I never expected to be. So of course I gathered a collection of wonderful beaver photos and passed them along with the understanding that they’d credit Cheryl Reynolds of Worth A Dam if they used them. Stay tuned for more of the story because we might be in a wildlife services pamphlet.
Think about that.
