Boundaries

This ecoregion extends from southeastern Alaska through southwestern Yukon, into western and central British Columbia, and northwestern Washington. The islands off the coast of the Alaskan peninsula and British Columbia, the Queen Charlotte Islands, and Vancouver Island also fall within this ecoregion.

Topography

This ecoregion stretches from the Rocky Mountains in the east to the Coast Mountains and Pacific Ocean in the west. Between these mountain ranges is the Interior Plateau, which is deeply intersected by lake and river systems in some areas, and opens into wide plains and rolling topography in other areas. This plateau has been subject to vast overflows of lava, the remains of which comprise the present-day soil. The mountainous regions are mainly composed of folded sedimentary and volcanic strata and massive metamorphic rocks of Palaeozoic and Mesozoic age. Glaciers still occur on mountaintops, and glaciation has filled valleys with glaciofluvial and moraine sediments. Elevations range from sea level to over 6000 m on Mount McKinley in Alaska and Mount Logan in British Columbia, the two highest mountains in North America.

Vancouver Island, the Queen Charlotte Islands and the islands of the Alaskan Peninsula make up the western extremity of the Western Cordillera, which consists of several parallel mountain ranges of varying height. In the northern part of this ecoregion, the Seward, Hubbard and Malaspina glaciers are the dominant physiographic influences, and the area is part of the largest nonpolar icefield in the world.

Freshwater habitats

Habitat types along the coast include sea stacks, sandy beaches, rocky coastal cliffs, coastal headlands, tidal pools, mud flats, salt marshes, streams, and rivers. On Vancouver Island small fast-flowing streams begin in the Vancouver Island Range and flow west through rugged, mountainous terrain into fjords and inlets of the Pacific Ocean, or flow east through rolling topography into Georgia Strait. Kennedy Lake, the largest lake on Vancouver Island, provides important spawning habitat for sockeye and other salmon. The Fraser River has its headwaters near Mount Robson where it collects runoff from mountains on both the eastern and western sides of British Columbia running through the Rocky Mountain Trench. It empties into the Fraser River estuary in the Greater Vancouver area, and is an important stopover for several million migratory birds each year. Its extensive mudflats provide important habitat for western sandpipers. The Copper River Delta (2,800 km²) is the largest contiguous wetland on the Pacific Coast of North America and is also an important stopover for millions of migrating shorebirds. The Skagit River (240 km) has both fast-flowing water through the Cascade Mountains and lacustrine habitat where it is impounded for 24 km at Ross Lake in Washington.

Terrestrial habitats

Coniferous forests are dominant in the ecoregion with such species as Pacific yew (Taxus brevifolia), larch (Larix spp.), western hemlock (T. heterophylla), western red cedar (Thuja plicata), white spruce (Picea glauca), Engelmann spruce (P. engelmannii), Sitka spruce (P. sitchensis), subalpine fir (Abies lasiocarpa), grand fir (A. grandis), lodgepole pine (Pinus contorta), western white pine (P. monticola), Douglas fir (Pseudotsuga menziesii), Garry oak (Quercus garryana), Pacific dogwood (Cornus nuttallii) and arbutus (Arbutus menziesii). The Skagit River’s rain-shadow climate supports Ponderosa pine (P. ponderosa) and wild rhododendrons. Broadleaf species such as black cottonwood (Populus trichocarpa) and red alder (Alnus rubra) replace the conifers along many rivers and streams. Mountain meadows, foothill grasslands and upper treeline/alpine communities also exist, with glaciers and icefields covering many northerly areas. Wet meadows are frequently found as part of the subalpine mosaic, with blueberries, dense moss, Indian hellebore (Veratrum viride), ragwort, hairgrass, and sedges.

Description of endemic fishes

The Vancouver lamprey (Lampetra macrostoma) in southern Vancouver Island is endemic to the ecoregion. Several other lampreys and sticklebacks appear to be endemic taxa, but have not been formally described as species. Because parts of Washington and British Columbia escaped glaciation during the Pleistocene, further study may reveal additional endemics. For instance, hot springs and caves, particularly on Vancouver Island, likely support many undescribed and potentially endangered invertebrates, including mites, mollusks, amphipods, and isopods.

Ecological phenomena

Many species in this ecoregion exhibit anadromy, including lampreys (Lampetra spp.), sturgeons (Acipenser spp.), smelts (Osmeridae) and Pacific salmon (Oncorhynchus spp.).

Justification for delineation

The ecoregions of Canada were identified based on the faunal similarity of 166 major watersheds based on a cluster analysis of freshwater fish occurrences in these watersheds. The Alaska and Canada Pacific Coastal ecoregion contains watersheds that drain all waters west of the continental divide in areas that were only deglaciated in the last 10,000 years. Therefore, the fauna is relatively young and limited to species present in Pacific and Beringian refugia during the last Ice Age.

The coastal islands within this ecoregion contain waterbodies that were formed since the retreat of the last Ice Age (ca. 10,000 years ago) and have been periodically inundated by the Pacific Ocean. As a result, the freshwater fish fauna is depauparate, but with several endemic species, and is comprised of species with some saltwater tolerance.

Level of taxonomic exploration

Good / Fair