Busy Beavers: Bringing Back Dam-Building Rodents to Protect Amphibians and Reptiles
Beavers are trains with teeth. You may know that trains were historically one of the biggest forces behind the expansion of industry and development in the US, and as a result, redefined the country’s landscape. Before trains, it was North American beavers.
Just as locomotive engineers have directed the movement of trains along the country’s tracks for centuries, North American beavers orchestrate the flow of river currents with dams and lodges. This has earned them a different but similar-sounding moniker – ecosystem engineers.
They were dubbed this title because, aside from humans, there aren’t any other species that have shaped the North American landscape more. While human development tends to result in fewer habitats and degraded landscapes, however, beavers create a diversity of habitats and improve habitat health (Goldfarb & Flores 2018).
For this reason, North American beavers may hold the key to the survival of some of the US’s most imperiled amphibians and reptiles.
These largest native rodents in the country were once nearly driven to extinction by the fur trade and their removal as pests. They’re now being hailed as environmental champions by many for the same reasons they were knocked historically. Beavers cause localized flooding of areas through the construction of dams and lodges constructed from tree branches, mud, and rocks, sometimes interfering with human development nearby, like buildings, agricultural fields, and irrigation systems.
However, their dams create ponds and other wetlands that serve as vital reservoirs during dry spells, effectively mitigating drought conditions (Goldfarb & Flores 2018). They also slow down the flow of water, recharging aquifers and causing excess sedimentation to drop out of the water column. Thus, beavers, as natural hydrologists, wield an incredible power to shape water systems.
While this is true for all regions, it’s especially true in the West, where water can be as ephemeral as youth. It’s hard for us to imagine how the country would have looked in the late 1600s with hundreds of millions of North American beavers spread across it, but we know it would have been much wetter.
That means there would have been a lot more habitat for many western wetland-dwelling amphibians and reptiles that are now imperiled and declining rapidly (Hossack et al. 2015, Romansic et al. 2020). In other words, the current lack of aquatic habitat isn’t only the result of recent, obvious reasons, like the construction of parking lots, but also because of unexpected and hidden causes that are legacies of previous generations.
We’re seeing, however, that this legacy of habitat loss for water-dependent amphibians and reptiles can be reversed when beavers are reintroduced. Species like the northern red-legged frog and northwestern salamander, which require longer periods of open water for breeding, are thriving in beaver-engineered habitats in Washington (Romansic et al. 2020). Beaver ponds provide the water levels these slow-developing species need throughout their critical life-cycle stages, helping to ensure their reproductive success.
In southern Colorado, two PARCAs, or Priority Amphibian and Reptile Conservation Areas, are home to a large number of vulnerable amphibians and reptiles that rely on wetlands and streams for at least parts of their life cycles. The Arkansas River and Southeast Canyon Lands PARCAs contain a staggering 18 at-risk species, many of which are dependent on aquatic habitat, a rare and dwindling commodity in the region.
However, North American beavers, which are already fairly abundant in parts of the state, provide a solution. Reintroducing them to areas of potentially prime habitat for species like the state-listed northern leopard frog would go a long way toward giving this frog its best chance. Researchers have demonstrated that these imperiled frogs prefer breeding in active beaver ponds because they lay their eggs in still, shallow water (Zero & Murphy 2016).
It’s not only amphibians that rely on the wetlands North American beavers create. Aquatic reptiles, including the western black-necked gartersnake and yellow mud turtle, both listed as species of Greatest Conservation Need in the state, need places to hunt prey and overwinter. An increased number of beaver ponds would be a boon for these and other at-risk reptiles.
Moreover, the benefits of North American beaver reintroduction extend far beyond those for amphibians and reptiles in Colorado (Hossack et al 2015). Beaver-engineered wetlands are hotspots of biodiversity, supporting a wide array of plant and animal life (Goldfarb & Flores 2018). These habitats are especially beneficial for declining fish like the native cutthroat trout subspecies in the state, which can move over dams during spawning and thrive in the high-quality water that results from the presence of beavers. The structural complexity of beaver ponds also fosters diverse communities of birds, mammals, and aquatic invertebrates.
If we want to recover these incredible wildlife species, it’ll require more habitat and connected areas to allow for gene flow among populations. While we can artificially create wetlands, restoring North American beavers to the landscape provides a more sustainable solution. Beaver reintroduction is much easier and more cost-effective than installing human-made ponds, especially at large scales.
Plus, beavers and the ponds they create provide a host of benefits to our communities–and our pocketbooks. They can alleviate the need for costly human-engineered flood control infrastructure. They act as carbon sinks, capturing carbon in their sediment and vegetation, helping to mitigate climate change. They provide us with beautiful places to enjoy, clean air and water and healthy soil, help stabilize water storage, reduce wildfire risks, and much more (Goldfarb & Flores 2018).
All of this is why we’ve started making plans for something that might not seem like an action that an amphibian and reptile conservation organization would be expected to take. Along with our partners at the Southern Plains Land Trust, we’ll be working on several North American beaver reintroduction projects in the Arkansas River and Southeast Canyon Lands PARCAs in southern Colorado in the coming years.
At ARC, we’re focused on improving ecosystems for at-risk species in the most strategic ways possible, whether by chainsaw, bulldozer, or…beaver. By embracing beavers as partners in habitat restoration, we’re paving the way for healthier ecosystems, sustainable water management, and a future where nature’s engineers thrive alongside amphibians, reptiles, and us.
References
Goldfarb, B., & Flores, D. (2018). Eager: the surprising, secret life of beavers and why they matter. Chelsea Green Publishing.
Hossack, B.R., Gould, W.R., Patla, D.A., Muths, E., Daley, R., Legg, K., & Corn, P.S. (2015).
Trends in Rocky Mountain amphibians and the role of beaver as a keystone species. Biological Conservation, 187: 260–269.
https://doi.org/10.1016/j.biocon.2015.05.005
Romansic, J.M., Nelson, N.L., Moffett, K.B., & Piovia-Scott, J. (2020). Beaver dams are associated with enhanced amphibian diversity via lengthened hydroperiods and increased representation of slow-developing species. Freshwater Biology, 66: 481-494.
https://doi.org/10.1111/fwb.13654
Zero, V.H. & Murphy, M.A. (2016). An amphibian species of concern prefers breeding in active beaver ponds. Ecosphere, 7:e01330.
https://doi.org/10.1002/ecs2.1330
