North Cascades Ecoregion
Description & Physiography
In the United States, the North Cascades Ecoregion features the high, rugged mountains of the Pacific Ranges. Highly dissected, glaciated mountain terrain up to 7,000 ft., punctuated by large, composite volcanoes rising to over 10,000 ft alternates with glacially-carved, U-shaped valley bottoms and cirques that extend down to only 500 ft. The Washington portion of the ecoregion contains the greatest concentration of active glaciers in the 48 conterminous United States.
The maritime climate of the Pacific Northwest, coupled with the large vertical relief of the mountains and volcanoes, produces frequent snowstorms and heavy snowfalls. The Cascades and Coast Mountains record some of the deepest snowfalls in the world. It is not uncommon for some places in the Cascades to have over 200 inches of snow accumulation. High elevations in the mountains are covered with snow for many months. Middle elevations have significant snowpacks that fluctuate over the course of the winter with rain-on-snow events. Lower elevations within the ecoregion accumulate little snow or have transient snowpacks. The annual averages of nearly 700 inches at some Cascades locations are some of the largest recorded at any measuring stations in the world. Inland precipitation decreases on the east side of the coastal ranges where less than 20 inches of precipitation accumulates per year.
Where the ecoregion borders the Strait of Georgia, the climate is characterized by generally mild temperatures that average 36-50º F throughout the year with summer means reaching 56º F in the Pacific Ranges. Rainfall is heavy, 30-150 in. per year, with a maximum in winter.
Plants & Animals
Climate is the major influence on vegetation types in the ecoregion. Vegetation is stratified by both elevation and precipitation. The windward slopes of the Coast Mountains and Cascades Range are covered in temperate rainforests. Conifers predominate and can grow to enormous size, especially on the moister, western slopes. The extreme variability of soils and geology, combined with extensive effects of glaciation and topography, have led to large localized differences in climate, species, natural communities and ecological systems.
At least 18 species of birds, mammals, butterflies and molluscs that occur within the ecoregion are federally, state, or provincially listed as threatened or endangered. In British Columbia, these species include the marbled murrelet, northern goshawk, peregrine falcon (Falco peregrinus), northern spotted owl, Townsend’s mole (Scapanus townsendii), Pacific water shrew (Sorex bendirii), mountain beaver (Aplodontia rufa rainiei and Aplodontia rufa rufa), fisher, Johnson’s hairstreak (Callophrys johnsoni), blue-gray tail dropper slug(Prophysaon coeruleum), dromedary jumping slug (Hemphillia dromedaries), evening field slug (Deroceras hesperium), Oregon forest snail (Allogona townsendiana), and Puget Oregonian (Cryptomastix devia). Listed species in Washington include the marbled murrelet, bald eagle (Haliaeetus leucocephalus), northern spotted owl, gray wolf, grizzly bear, fisher, and lynx. The Puget Oregonian, a snail that was native to British Columbia, Washington and Oregon, was last noted in British Columbia in the early 1900s and is now considered extirpated from Canada as a result of the loss of low elevation older forests. The grizzly bear, gray wolf and fisher appear to be extirpated in Washington. Many more species are listed as species of concern in the U.S. or Washington, are blue-listed in British Columbia, or are listed as species of special concern in Canada.
Humans & History
Because their greater inaccessibility made it more difficult to cut and transport the timber, the Coast Mountains and Cascades Range were some of the last areas to be logged in the Pacific Northwest. Other than logging and a large ski resort at Whistler, most of the land in the ecoregion is relatively undeveloped; however, this situation is rapidly changing as the corridor between Vancouver and Pemberton undergoes development in preparation for the 2010 Winter Olympics. The fishing industry also plays a major role in the economy of the BC portion of the ecoregion, and historically, the Coast Mountains and Cascades were important areas for gold mining. Sand and gravel extraction operations are important economic contributors in the ecoregion.
Less than 1% of the ecoregion is under Aboriginal/tribal landownership. In Washington, much of the ecoregion occurs within the ceded lands and usual and accustomed fishing areas of tribes. Usual and accustomed areas are judicially defined areas where tribal members have fishing rights based on their tribe’s historical use patterns. Tribes in Washington manage tribally-owned lands on reservations and are actively involved in monitoring, research and management activities on ceded lands. Tribes are also active participants in discussions about natural resources management and conservation activities within their usual and accustomed areas. In British Columbia, the North Cascades ecoregion is covered by 11 First Nations Statement of Intent areas. Statement of Intent areas are the delineations of traditional territory boundaries for those Nations involved in treaty negotiations with the provincial government.
As of 1991, less than 2% of Washington’s portion of this ecoregion had been converted to urban and agricultural development. Although most of the area of these counties is located within the ecoregion, most of the population base is located outside, closer to the coast and urban areas such as Bellingham, Mount Vernon, Kent, and Seattle. Total population of the four counties within the ecoregion is less than 8,000. Most of the population lives along river/highway corridors that reach into the ecoregion or run from one side to another through mountain passes. Recreation and second homes have a significant influence on these developing corridors.
More than 96% of the Washington portion of the ecoregion is uninhabited and uncultivated, and has the lowest human impact of any of the state's terrestrial ecoregions. Protected areas account for about 47% of this portion of the ecoregion. Large areas are protected in North Cascades National Park and Ross Lake National Recreation Area, and in several wilderness areas. Logging has occurred widely at lower elevations in the ecoregion. Recreational activities that occur in this portion of the ecoregion include hunting, fishing, hiking and snowmobiling.