It sounds counterintuitive, yes.
First, a quick refresher: Beavers do not build dams to protect our towns and cities from flooding. They do so to create ponds that are deep enough to keep themselves and their families safe from predators and harsh winter conditions. Sometimes they build one big dam, sometimes a series of smaller dams, and sometimes- depending on the habitat- no dams at all. Beaver dams are sturdy structures, but they are ultimately temporary.)
Through their dam building, tree felling, and canal digging behaviors, the collective changes beavers make to a freshwater landscape are referred to as a ‘disturbance regime.’ Beaver examples of natural disturbances are some of many examples of inevitable change that occur within an ecosystem. Beaver wetlands can be thought of as natural infrastructure that can withstand increasing precipitation rates and a changing climate, as they have done before.
As Fairfax and Westbrook wrote in a recent paper, beavers “can create locally climate-resistant landscapes through their ecosystem engineering activities” and are therefore “capable of ameliorating climate change on much larger spatiotemporal scales that affect a multitude of other species, including humans.” (2024, 330-331) This question of scale is key in understanding how beaver wetlands prevent flood damage.
The small floods beavers create within a watershed, in places where there is little to no human infrastructure, act like a series of sponges soaking up rainwater as it moves downstream. This slowing down and spreading out of water essentially results in less water taking more time to reach areas with more human development. In other words, beaver wetlands store excess water upstream so it causes less damage downstream. Recent studies (within the last five years) found that North American (Castor canadensis) and Eurasian (Castor fiber) beaver wetlands decrease erosion, delay floodwater transmission, reduce stream ‘flashiness,’ and diminish downstream flood damage at sites in Canada and the UK. For example, in England, beaver dams reduced up to 60% of average flow rates during storm events compared with those before beavers were reintroduced.
Here is a simple video which demonstrates this concept visually:
Admittedly, there are limitations to ‘using’ beavers for flood mitigation:
- Beavers do nothing to help the people currently suffering in the wake of devastation from Hurricanes Helene and Milton, and other natural disasters.
- Beavers are not a magical solution to save us from climate catastrophe. This is not within their capacity; nor is it the responsibility of any other species to right what we, collectively, have wronged.
- Beavers in human-created drainage systems (like many HBCF project sites) do not provide these flood attenuation benefits. We must allow beavers to create and maintain their own wetlands.
- Beaver floods can cause people problems such as property damage. The locations of beaver dams and their proximity to existing human infrastructure is a critical consideration.
Despite these limitations, allowing the wetlands beavers create to prevent flood damage during and after increasingly common storms is a promising example of ameliorating one severe impact of climate change. Coexisting with beavers is one small way we can participate in multi-species climate change adaptation and resilience.
A note on beaver dam analogs (BDAs): While mimicking beaver dams by installing BDAs is a popular stream restoration trend, HBCF is focused on promoting coexistence with the beavers already thriving in our region so they can reproduce and naturally disperse to areas that need them.
More videos:
References:
- Auster, Roger E., Stewart W. Barr, and Richard E. Brazier. “Beavers and flood alleviation: Human perspectives from downstream communities.” Journal of Flood Risk Management 15.2 (2022): e12789.
- Druschke, Caroline Gottschalk, et al. “Re-centering relations: The trouble with quick fix approaches to beaver-based restoration.” Geoforum 156 (2024): 104121.
- Fairfax, Emily, and Cherie Westbrook. “The Ecology and Evolution of Beavers: Ecosystem Engineers that Ameliorate Climate Change.” Annual Review of Ecology, Evolution, and Systematics 55 (2024).
- Puttock, Alan, et al. “Beaver dams attenuate flow: A multi‐site study.” Hydrological processes 35.2 (2021): e14017.
- Westbrook, Cherie J., Amanda Ronnquist, and Angela Bedard‐Haughn. “Hydrological functioning of a beaver dam sequence and regional dam persistence during an extreme rainstorm.” Hydrological Processes 34.18 (2020): 3726-3737.