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Western Cordillera

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Map Legend & Subregion List

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NameColor on MapCEC Code*
Cascades6.2.7
Blue Mountains6.2.9
Northern Rockies6.2.3
Idaho Batholith6.2.15
Middle Rockies6.2.10
Wasatch and Uinta Mountains6.2.13
Southern Rockies6.2.14
Canadian Rockies6.2.4
Sierra Nevada6.2.12
North Cascades6.2.5
Klamath Mountains/California High North Coast Range6.2.11
Eastern Cascades Slopes and Foothills6.2.8
Skeena-Omineca-Central Canadian Rocky Mountains6.2.1
Chilcotin Ranges and Fraser Plateau6.2.2
Cypress Uplands6.2.6

* This code refers to the CEC's Level 3 ecoregion codes for North America, see here.

About the Western Cordillera

The Western Cordillera is a mountainous region in Western North America covering most of the Rocky Mountains. The region extends from British Columbia and southwestern Alberta, through several discontinuous pieces in most states of the western U.S., with the southernmost parts of this region extending into California and northern New Mexico.

Topography is steep, reaching heights over 14,440 feet (4400m) in Colorado, with elevations over 10,000 feet (3000m) occurring across the region. The climate varies considerably, both with changing altitude, and changes in microclimate on different-facing slopes. Precipitation is mostly generated from orographic lift, as moisture-laden air masses from the Pacific move west-to-east, cooling as they ascend mountains. Snowfall followed by melting supplies the moisture for streams and rivers which flow out of this region into other, more arid areas of low elevation.

The climate ranges from arctic and subarctic at the higher elevations, through alpine climates, to humid continental climates at mid elevations and semi-arid continental climates at lower elevations. As one ascends in elevation, temperatures become cooler, but temperature swings more extreme, and precipitation increases.

Cover here ranges from barren and snow-capped mountains with numerous rocky outcroppings at the highest elevations, through coniferous forest to mixed forest at lower elevations, and to grass or scrubland at the lowest elevations. Although the species diversity in many of these specific habitats is lower, the region as a whole is high in biodiversity owing to the great diversity of climate and cover type. The island-like nature of many of these regions, surrounded by dissimilar ecosystems, leads to a lot of endemic species, although fewer than milder areas farther south. At the same time, many cold-tolerant species are found here that also occur across a wide range of boreal forest in the Northern Forests and Taiga regions. The richest forest growth occurs at mid elevations, high enough to provide sufficient rainfall, but not so high that cold temperatures stunt plant growth.

Most of this region is surrounded by more arid areas at lower elevations, mostly the Cold Deserts of the interior west. To the east, at lower elevations, lies the Great Plains, more specifically the West-Central Semi-Arid Prairies in the northern U.S. and the South Central Semi-Arid Prairies in the south. However, in Canada, the east of this region is bordered by the still-forested Boreal Plain, and this border shares many plant species in common as both regions have sufficient moisture to support forests. The southernmost border of this region on the West Coast borders the wetter and milder Marine West Coast Forest, and farther south, the drier but milder Mediterranean California. The border with the Marine West Coast Forest is more gradual (except where separated by very high mountains in Canada) and there are more plant species shared in common between these areas as well.