The Beaver Way
In the recovering floodplain of the Clark Fork River, the makers, methods, and materials of this dam offer hope for the next century, and beyond. (Photo Credit: Rob Rich)
Near Missoula, Montana, where Deer Creek tumbles out of the Sapphire Mountains and winds through the floodplain of the Clark Fork River, the signs are clear. Tight grooves in the sharp-angled tips of young alders and willows reveal the work of teeth. Some of the bright, bark-shorn stems lay scattered in the water, where they lap in the shallows’ slow pulse. Other stems are woven into the flow-locked lattice of a dam, bound with pressed mud. A person might encounter the scene without surprise, merely thinking that beavers were busy.
But today, during earth’s sixth extinction, we cannot forget the feat of existence. Paleocastor, a terrestrial beaver genus whose members tunneled corkscrews into grasslands with teeth, blinked out some 23 million years ago. Castoroides, a bear-sized beaver genus whose members never built dams, succumbed about 10,000 years ago. Thirty-one of these former beaver genera failed to adapt to their rapidly changing climates and predators, but our continent’s sole survivor – Castor canadensis – has faced its gauntlet, too. Over the last seven million years, the North American beaver has not only endured the Pleistocene, but also the Fur Trade – a mammalian massacre where, in three short centuries, people collapsed a population of 400 million beavers to a mere 100,000, all in their zeal for money, power, and hats.
And, for most of the last century, beavers skirting those threats would not have found refuge at Deer Creek, which was drowned by the waters of the Milltown Dam. This was especially the case when, soon after the Dam’s completion in 1907, copper, silver, and gold mines near the Clark Fork headwaters flushed arsenic-laden sediment downstream in a historic flood. The Milltown Dam was fortified with more concrete, steel, and permanent intentions, but the noxious tailings stacked up steadily behind the impoundment, for decades. It was not until 1983, with the local aquifer poisoned and the swollen threat of another toxic flood knocking at the aged edifice, that the Environmental Protection Agency deemed 120 miles of the once-thriving river a Superfund site and, ultimately, decreed the Dam must fall. In 2008 the deed was done, over six million cubic yards of the contaminated sediment were shipped back upstream for reburial, and the water finally flowed free.
Scientists have called on beavers as vital agents of rewilding who can help connect and protect our landscape. We’re a few centuries removed from the time when beavers carved the land we now see, but if we learn to identify, interpret, and respect the evidence they left behind, we will be ready to embrace their return. (Photo Credit: Rob Rich)
To see beavers build against that recent history might conjure a hint of irony, but at the core it’s a second chance, in perfect tune with deep time in this place. Raw and ready for something new, the recession of the region’s last glacial lake – some 13,000 years ago – must have been similar to the scene of the Milltown Dam’s drained reservoir. But in contrast to the Milltown Dam’s wholesale conversion of flowing water, a beaver’s damming creates nuanced complications of flow, with currents riven by multi-thread channels. By watering the soils and dispersing plant cuttings, such beaver damming is a spark of plant succession, which in turn draws animals seeking food, shelter, and connectivity. Today’s science shows that 80 percent of the American West’s biological diversity occurs on the 2 percent of its land that exists in riparian habitats, but for millennia it’s been plain to see that life thrives in the beaver’s braided hydrologic mosaic.
Just as a fire-adapted forest needs a periodic flame for renewal, North American waters need beavers to be whole. From Alaska to Mexico, beavers have conditioned the pieces, patterns, and processes that drive freshwater communities (and even coastal ones, as seen where beavers are trapping tides and helping fish amidst new sediments released in human dam removals on Washington’s Elwha River). Beaver dams might sprout, rot, or leak, but as our climate change and biodiversity crises clamp down across the planet, beavers are reminding us that the best dams don’t merely hold the most water. The best must go beyond that, by bridging habitats, buffering extremes, and maximizing benefits to myriad links of life. We may have once thought that rivers could be straightened and beavers could be outdone with impervious, enormous, and calibrated bulwarks of concrete, but as record droughts and floods expose the risks of fast flows and mass storage, the merits of a more dispersed, sinuous, and spongy approach becomes clear. More than products of static or efficient perfection, we need the beaver’s dynamic, adaptive process.
When a beaver’s chiseled teeth gnaw down a shrub’s leading stem, the plant distributes a growth hormone called auxin to other shoots, each which reach for the light. Thanks to millennia of beaver-plant coevolution in North America, this knack for regeneration is especially strong in riparian hardwoods like willows and cottonwoods, or this speckled alder (Alnus incana). (Photo Credit: Rob Rich)
The Clark Fork floodplain is just one place to remember what’s possible when we respect the beaver’s way. They don’t aim to spite us or save us, but their singular anatomy and behavior has shaped our shared ecology. Most all the watersheds we draw from daily to drink, wash, and flush were shaped by beavers before us, and the debt we owe is deep. But we’re learning. Fencing and flow-device tools to prevent beaver-human conflicts are on the rise, and each new installation is expanding nonlethal solutions for a culture of coexistence. With low-tech process-based restoration, human stewards are learning to think – and act – in the beaver way, too. Using simple cutting and digging tools, plus a dose of semi-aquatic craftsmanship, folks are strapping on waders and sloshing out to pound posts, weave branches, and schlep mud into handmade dams, which can reconnect incised streams with floodplains in degraded arid lands. Such mimicry can spur beavers to overcome obstacles have prevented their recovery and, at its best, this approach can entice beavers to stay and enhance the renewal. In these places, and everywhere, even one fresh beaver-chewed stick can start us the right direction, as each grooved cut asks us to recall how untold numbers of sticks have brought health, resilience, and diversity to watersheds through time. Beavers have made and remade this continent by these subtle yet significant means, and when we consider how many lives are touched by the work of their teeth, we can see this is not just busy work. Fifteen years out from the Milltown Dam’s fall, we can sense that beavers hold the old way to a better future.
The Montana Beaver Working Group consists of diverse, statewide stakeholders advancing the beaver’s keystone role in watershed health. Through varied efforts in policy reform, non-lethal conflict resolution, habitat restoration, and more, the Group’s participants are creating the context for beavers to recover. Many of its projects often start and end with good monitoring, and this collaborative beaver habitat survey empowered youth scientists to document beaver habitat that would guide conservation in the Lolo National Forest. (Photo Credit: Florie Consolati)
Rob Rich is a field naturalist who conducts biological surveys, advances conservation projects, and teaches courses on wildlife tracking, beaver ecology, birding, and more. He currently serves the National Wildlife Federation’s coordination of the Montana Beaver Working Group, and he has also worked for entities including the Montana Natural History Center, Swan Valley Connections, and the University of Montana.