What If Gone

Species → North American Beaver

North American Beaver

Castor canadensis

12,500,000 individuals
Extinction risk Least Concern
Ecosystem engineerWetlandWaterway
North American Beaver (Castor canadensis)
Photo: Ryan Hodnett, Wikimedia Commons (CC BY-SA 4.0)

What if it disappeared?

Impact Major
A few years

Without beavers building dams, a riparian corridor would lose the elevated water table, ponds, and transformed vegetation that beaver activity sustains today.

Documented
Detail

Naiman, R.J., Johnston, C.A. et Kelley, J.C. (1988). Alteration of North American Streams by Beaver. BioScience, 38(11), 753–762.

The authors show that beaver activity affects the physical structure of streams (channel morphology, vegetation), the diversity of habitats and species that depend on them, and functions such as stream productivity and resistance to disturbance — making the beaver the textbook example of the 'ecosystem engineer' concept.

A decade or more

A riparian corridor without beavers loses the wildfire buffer their engineering provides: beaver-dammed corridors stay noticeably greener during a wildfire than comparable corridors without beavers — an effect measured by satellite imagery across many real wildfires in the western United States.

Documented
Detail

Fairfax, E. et Whittle, A. (2020). Smokey the Beaver: beaver-dammed riparian corridors stay green during wildfire throughout the western USA. Ecological Applications, 30(8), e02225.

By comparing, across many real wildfires, beaver-dammed riparian corridors to comparable corridors without beavers, the authors show that dammed areas stay green and wet while neighboring areas burn. Without beavers, the wetlands that produce this effect don't exist — and take years to form after beavers disappear or return.

Several decades

Across most of its historical range, where beavers remain absent after centuries of trapping, this wildfire buffer does not exist at the watershed scale: at full restoration capacity, beavers could store considerable volumes of water there and extend that buffer — a potential that remains largely untapped until the species returns.

Extrapolated
Detail

Modélisation à l'échelle de la Sierra Nevada (2025) évoquée dans la littérature sur la restauration du castor — potentiel estimé à 120 millions de m³ de stockage d'eau et 2 200 km² de résilience au feu, alors que la capacité de barrage actuelle ne représente qu'environ 51 % du niveau historique dans cette région.

These figures are a projection of what would be possible if beaver populations regained a much larger share of their historical damming capacity — not a measurement of what exists today. This is restoration potential, not an effect already achieved.

What's missing to confirm it: The actual pace of beaver recolonization in the coming decades — and thus the time before a significant share of this potential materializes — remains uncertain.

Documentation

Last verified: August 6, 2026

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