What do you know! Two days ago the US forest service published a collection of articles about riparian restoration, and guess what number seven was? The summary of Suzanne Fouty’s very beavery dissertation. You can download the whole thing online but I’m going to give you some highlights here to whet your appetite for the original.
Chapter 7. Euro-American Beaver Trapping and Its Long-Term Impact on Drainage Network Form and Function,Water Abundance, Delivery, and System Stability
Suzanne Fouty, Ph.D.
Euro-American (EA) beaver trapping was a regional and watershed-scale disturbance that occurred across the North American continent. This concentrated removal of beavers altered drainages by creating thousands of localized base-level drops as beaver dams failed and were not repaired. These base-level drops led to the development of channels as ponds drained and water eroded the fine sediment trapped behind the dams
(Dobyns 1981; Fouty 1996, 2003; Parker et al. 1985). The speed at which drainages transformed from beaver-dominated to channel-dominated varied as a function of climate, upland and riparian vegetation, and the subsequent land uses. As the drainage network pattern changed, flood magnitudes and frequencies increased and base flows decreased, creating stream systems much more sensitive to climatic variability.
Using current research and historic observations, I developed a conceptual model describing the geomorphic and hydrologic response of a drainage basin to the entry of beavers and then their removal or abandonment (Fouty 2003).
Now there are lots of parts of this research that are way over our heads, but the gist is the Suzanne used a model to systematically determine how much water was lost in parts of the US when beavers were eliminated. She challenged the work of those who said had said for years that the effect of their loss was minimal.
You know me, I can only understand the pictures to understand. This is an excellent break down of why beavers matter on the landscape. Use it to convince your hydrological skeptics. Suffice it to say that from a surface and ground water perspective beavers make things a lot more habitable and life supporting.
She finishises with a big bang of course.
Separating out cause-and-effect relationships in fluvial systems is challenging because changes to their form and function are the result of many factors interacting over time and space. This chapter explored some of those factors in its examination of how EA beaver trapping altered the appearance and hydrologic behavior of stream systems and why the influence of beavers and beaver trapping were missed in the discipline of fluvial geomorphology until recently. It also examined how information gaps led to the development of relationships of process and form based on observations and measurements
of channelized drainages and altered uplands that created conditions whereby water was rapidly shed from the landscape rather than stored and released slowly.
Given the magnitude of the historic changes and their hydrologic consequences, the scale of restoration and the rate at which it must occur is enormous if the impact of climate change on water availability, and the systems that depend on water, are to be minimized. Partnering with beavers to restore the water-holding capability of our stream corridors would rapidly dampen fluctuations in the abundance and scarcity of water and leave wild and human communities less vulnerable. Efforts will require broad public support and an integrated approach by State and Federal agencies given their respective areas of influence and impact. Scientists are in a position to help inform the discussions by sharing what we have learned about how past and current land uses affect the ability of the landscape to naturally store water for future use; however, our effectiveness will first require that we change the lens we have been looking through. Because the discipline of fluvial geomorphology has internalized and codified degraded systems as normal, our stream restoration efforts fall short. By placing these fluvial geomorphic relationships within their historic disturbance context, one that includes EA beaver trapping, new strategies, approaches, and partnerships emerge that are essential for restoration to successfully occur. This new lens reveals the essential role beavers play in this recovery process.
Basically the paper concludes with “you were all WRONG (And I’m looking at you Aldo & Luna) because you assumed a landscape stripped of beavers was the norm. Listen to what I’m saying because climate change is gonna knock the spit out of all of us. And beavers can help.”
I hope she doesn’t mind the paraphrase. But go read the original. And pass it on.
