Beaver in tidal marshes of the Pacific Northwest

Beaver are considered fluvial or lacustrine animals, whose dams convert lotic habitats into lentic ones. This produces extensive changes in ecosystem structure and processes so that beaver are considered quintessential ecosystem engineers. I broaden our understanding of beaver by describing their widespread presence in tidal river deltas and estuaries of coastal British Columbia, Washington, and Oregon, where tides can range between 1.5 and 5.0 m. These observations expand the known habitat distribution of beaver and invite investigation of the ecosystem consequences of beaver in tidal ecosystems. Early research shows that one of these consequences is a quadrupling of the amount of low-tide pool habitat in tidal marsh channels, where these low-tide pools support three times the density of juvenile salmon as do low-tide shallows. Low-tide beaver pools are likely areas of low salmon predation, high feeding, and long residence time—all leading to improved growth and survivorship of juvenile salmon.