Beaver Dam Bonus

So I published a post too soon and didn’t have anything ready to go for my usual Sunday slot. As I sorted and processed recent photos, I decided to put together this bonus post with pictures I hadn’t planned to write about.

I almost didn’t do it when I saw the potential because I don’t have a ‘before’ shot which seriously bums me out. The comparison in my mind exists, but I can’t show you how easy it was to cross where this big dam now sits.

But Kenneth Casper, The Wisconsin Explorer can, check it out. This is now –

And this was how it was until just 2018 or so –

The dam is now on those rocks that were easy to cross. Just out of the shot to the right was an older dam that had already been breached. Not sure if that was by humans or by neglect, but you can’t see it anymore. Like everywhere else, beaver numbers are down from pre-European invasion totals, and Wisconsin has two trapping seasons during the year. Permits are required and certain areas are excluded though. I agree that as rodents capable of wreaking serious physical change on the landscape they shouldn’t become too numerous, but I also I think the benefits they provide is worth having more of them around.

A little while ago I read Eager: The Surprising, Secret Life of Beavers and Why They Matter by Ben Goldfarb and it was quite eye-opening. One thing that is pretty powerful is how the ponds sequester not just surface water, but ground water as well. The sheer weight of a beaver pond forces water underground and holds it there where it can replenish aquifers and other ground water collection areas. Imagine the effect in places with little rainfall. Especially where the trees and other native plants are gone and there is only farmland. Think of how high the water table could become with a little beaver involvement. You’d think farmers and ranchers would dig this.

But what about the fish??!!

Yeah, people love a running stream and so do I. Just downstream of this big pond is a brook I love to photograph and I hope it remains running strong. Anglers do too and in the past have dynamited beaver dams to keep things moving. But that doesn’t do the fish any favors. Beavers and fish have evolved together. That’s important. Many fish species need different depths, temperatures and water movement, sometimes in one lifetime (fry need one thing, adults another for example). A completely open, continually running creek is basically one-dimensional. There aren’t different conditions anywhere except by accidents like fallen trees. Beavers provide these variables in a more stable and long-term way.

By widening and deepening running water channels, they provide more constant temperatures and slower areas for hiding, breeding, eating and just doing fish stuff. And yes, breeding fish who need to migrate upstream can overcome beaver dams. They’ve been doing it for hundreds of thousands of years. It’s human dams that are the problem.

That said, this dam is a little bit of a problem…for the Ice Age Trail. This is one end of the Turtle Rock segment. It was rerouted in 2018 or 19 when the beavers really started working to build a new dam. The updated trail created downstream was squishy, but doable. Now it’s a real challenge. I made it through (as a future post will show), but I had to gather and place some big branches over wide sections of water flow and it took some creative bending, stretching and ducking to get through other parts. In the Wall of Wood shot above you can kind of see the secondary dam in the background. I think it’s there to assist the beavers to float branches back to the primary dam. You have to cross behind that. Off to the left I found their garden –

Another thing I learned from the book is that beavers rotate where they fell trees. Of course it has to be close to their lodges and dams, but they don’t stay in one area until it’s depleted. They move from one place to another to acquire building materials and food. Food is small branches and leaves which they submerge underwater for winter since they aren’t true hibernators and need it all winter long.

The area of popple they’re using was created when humans came and clear cut this section of forest leaving basically nothing behind. Aspen and poplar are light hungry and fast growing, not to mention prolific seed-scatterers, so they are the first to claim open territory created by clear cutting. Then the beavers come and do some cutting of their own. If it was a mature forest it wouldn’t look this open. Beavers don’t need or accidentally destroy forest in this way, but they certainly do make big changes. Soon this open space will fill back in, probably with more popple, but maybe there will be a lucky conifer or oak that can get some growth before the shade closes in again.

The lumberyard is a bit too far away from the pond itself for sedges or other marsh-loving plants to develop, but it they have grown along the older banks of the pond and provide habitat for many animals and birds. It’s one of the most productive environments on earth.

Beaver dams also slow flooding and erosion which people may not realize because they only pay attention to the immediate area where the pond is made. But beavers can’t control water indefinitely. They will build to create a stable and large enough home for themselves and their kits, but that’s it. When they decide the dam is high enough, the outflow will stabilize and more defined water channels will develop.

In the meantime I’ll have to risk wet feet or find ways to stay dry if I want to continue to visit my favorite little brook on the Turtle Rock segment of the Ice Age Trail.