Overall, our Beaver, Natures engineer, does more good than bad in it's dam building and resulting pond creation that yields verdant "meadows of grass" and outstanding habitat for multiple creatures in the System................The man made structures we erect in the "wrong places" can be done in by our "eager beavers".......Nonetheless, nice to know that this once near exterminated keystone animal once again swims to the tune of nearly 20 million strong in the USA

 

Essay: The Good Beaver and The Bad Beaver

An Idaho writer on how a beaver dam revived a pasture on his property and then nearly ruined it.

By Dennis Higman
As Jon Marvel of Western Watersheds Project in Hailey, Idaho, once told me, there are good beavers and bad beavers. That is, beavers can do a great deal of good in the natural environment by impounding water that eventually creates fertile meadows, but these tree-cutting, dam-building critters can also do a great deal of harm to a man-made environment, particularly if that man happens to live on a flood plain.
The North American beaver (Castor Canadensis), once some 90 million strong, was almost trapped out in the West to supply hats and coats to English lords and ladies by the likes of Donald Mackenzie and Alexander Ross, who passed through our neighborhood in southwest Idaho in the early 1800s, leaving behind little of value beyond a few maps and place names such as Fort Hall.  Like the buffalo, however, the intrepid beaver has made a comeback of sorts. Today there are an estimated 15 million to 20 million in the United States, so they aren't on anybody's endangered species list. Nor do they, like the gray wolf, have well-organized groups of political advocates and ecologists passionately promoting their cause as an essential, integral part of a balanced environment.
The industrious beaver as a symbol is still popular enough. It's on the crest of the Canadian Pacific Railway and remains the mascot of Oregon State University and Cal Tech, among other institutions. But somehow, as one of the most important foundation species affecting the conservation of our most precious resource in the arid West—water—the beaver gets decidedly mixed reviews from those of us who live with them in our backyard.
My wife and I viewed the beaver as nothing but good, however, when they showed up unannounced and started building dams across the creek that runs the length of our lower pasture. After decades of unrestricted cattle grazing, the creek was an environmental disaster when we moved in, a roaring muddy torrent in the spring that slowed to a trickle and looked like a lifeless ditch by late summer.
Back then, we didn't know anything about the critical importance of secondary watersheds and riparian zones in this high mountain desert of sage, aspens and willows where the annual rainfall, in a good year, is 6 inches. We were city people, transplants from the West Coast, where rainfall is 34 inches in a normal year. Nor, as it turned out, did we know much about beavers.
What we did know was we didn't like the looks of either the stream nor the barren hammered dirt littered with piles of cow dung surrounding it, so the first thing we did was fence out the cattle. Then we set about trying to change the property more to our liking. Over those first few years, we dumped truckloads of rocks at various intervals in the steam to slow it and harrowed in a variety of grass to speed up growth in the pasture, but it was slow going. Spring runoff topped our artificial dams, which failed to hold back much water in the fall. Very little grass came up in the pasture, and the tentative, scattered green shoots that did, promptly shriveled up. We even shoveled up acres of cow dung to clear the ground and encourage growth, much to the amusement of the good old boys who helped us build our house on the hill. "Just leave it alone," they laughed. "Eventually it will go away."
Someone with a lot of knowledge about cattle grazing told me that once cattle were removed, the land would have a good chance of recovering on its own within 10 to 15 years. We were impatient, however, so when the beavers showed up midway through this long recovery process, we greeted them like saviors. Almost immediately their new dams created ponds that blocked the worst of the runoff and miraculously maintained an even flow in the fall.  Grass seemed to take hold almost overnight, our brown pasture turned green, and Rainbow trout began to appear in the ever-expanding ponds.
Living high on the hill overlooking this idyllic scene, it appeared to be a win-win for all of us, including a cow moose that had a calf the next spring in our lush pasture andducks of all kinds that settled on the ponds. Red-Wing Blackbirds lived in the bushes along the banks, and garter snakes preyed on the swarms of tiny bugs that skimmed along the surface of our creek that now was beginning to meander across the pasture.
Watching this transformation by beaver, we began to understand that the thousands upon thousands of secondary streams like ours across the arid West, where every drop of water counts, and the healthy riparian zones created by them, are amongst the most precious natural assets we have. They not only create surface water supporting a diversity of wildlife, fish, birds and bugs, but maintain the long-term supply of groundwater, aquifers that provide, among other things, water for our well some 260 feet below the surface.
We seldom saw the industrious furry little engineers that made this all possible (and some are not so little, weighing as much as 55 pounds) because they worked by night. But in the morning we would go down to admire their handiwork and marvel at the size and scope of their expanding operations—willow clear-cuts that would have made a logger proud and complex dams of sticks and mud and fist-size stones that grew higher and higher as the ponds grew wider and deeper.
And then one morning, we found that they'd built a small dam to one side that was threatening to flood the only structure we had in the pasture, a storage shed containing stuff that wouldn't fit in the house—tables and chairs, a King sized bed, a couple of racing bikes and a lot of art. The shed was too big to move, so I reluctantly hooked up a grapple and chain to the pickup and tore the dam out. We figured the beavers wouldn't miss this one little dam when they had so many others. 
We figured wrong. The next morning the dam was not only rebuilt, but it was wider and taller than ever and there was a stockpile of sticks in the pond behind it ready for installation the next night. Determined not to let a mere rodent beat me down, I not only tore it out again, but spent the better part of a day in waders making sure everything that connected it to the bank was uprooted as well. 
The result, predictably, was yet another bigger, stronger dam the next morning, creating a miniature lake that was getting very close to floating our storage shed away. Clearly we were going about this the wrong way, so we looked for a humane solution on the internet and found "have-a-heart"-type live traps, and "beaver bafflers" and "pond levelers" involving various configurations of pipe.
We also sought advice from Mike Foster, local wildlife biologist with the U.S. Forest Service.  He noted that to trap them out, humanely or otherwise, required getting them all, which would be difficult because we only owned a relatively small piece of the creek. However, he recommended trying the pond leveler idea with the caveat that, in his experience, they required frequent maintenance to keep the pipes clear.
As it happened, we had two pieces of 6-inch PVC pipe about 8 feet long, one perforated and one not, so I tore a hole in the middle of the dam and put these about half way down, with one end extending into the pond well above the bottom and the other sticking out of the other side of the dam, well above the creek.
The next morning, although the dam had been rebuilt around them, both pipes worked like a charm. Water was pouring through, lowering the pond to acceptable levels.  The question was, of course, how long would it continue to work?  To our great joy, both pipes were still running hard a week later, although the industrious beavers had already begun cleverly building up the bottom of the pond with rocks and mud so they could reach the pipe inlets and block them.
Clearly this was going to take them some time so, in the interim, we could step back and take solace in the fact that we had fought them to a draw, at least for the moment.  And if it wasn't exactly a win-win, it was close enough. We had done our best to accommodate the "good beaver" and come to terms with the bad.