West Cascades
Description & Physiography
The West Cascades Ecoregion extends west from the Cascade Crest to the Puget Sound and Willamette Valley lowlands and from Snoqualmie Pass south across the Columbia Gorge to the Klamath Mountains in southwest Oregon, almost to the California border.
Geologically, the West Cascades Ecoregion has two distinct areas: the younger volcanic crest (approximately 3 million years old) composed of prominent mountains, and the "old Cascades" to the west of the crest in Oregon, and interspersed in Washington (at least 30 million years old).
The older mountains feature long ridges with steep sides and wide, glaciated valleys, and remnants of long-extinct volcanoes. Isolated younger volcanic peaks such as Mount St. Helens, Mount Rainier, Mount Hood, Mount Jefferson and the Three Sisters, rise above surrounding steep mountain ridges. These younger mountain peaks were formed primarily from extrusive volcanic activity.
Natural lakes are numerous, with most being created by glacial processes and landslides. Small, steep-gradient streams feed major rivers, and most of them in Washington drain into the Puget Sound. In the northern two-thirds of the ecoregion in southwestern Washington and Oregon, streams flow into the Cowlitz, Lewis or Willamette Rivers, and then to the Columbia River system; the southern third of Oregon’s West Cascades drains to the Pacific Ocean through the Umpqua and Rogue River systems.
Climate
The climate varies with elevation and, to a lesser extent, latitude. Higher elevations typically receive heavy winter snows. In general, the climate of this ecoregion is wet and relatively mild. Average annual precipitation ranges from about 55 to 140 inches. Most precipitation occurs from October through April. The highest elevations are continuously covered with snow for the winter months. Middle elevations have significant snow pack that fluctuates over the course of the winter with rain-on-snow events. The lowest elevations accumulate little snow and generally have a transient snow pack. The drier parts of the ecoregion in southern Oregon have a fire regime more similar to the Klamath Mountains, with frequent lightning-caused fires. In the northern part of Oregon and southwestern Washington, the natural fire regime historically produced less frequent but more severe fires. In northern Washington, natural fires rarely occurred.
Plants & Animals
Wildlife species richness is not as high in the West Cascades as it is in other temperate conifer forests, however the ecoregion is notable for comparatively high amphibian endemism. A diverse range of plant species including numerous endemics are found in the ecoregion but are especially concentrated near Mount Rainier in Washington and the Columbia River Gorge.
A number of amphibian targets are either West Cascade endemics or have a limited distribution. The Cascades torrent salamander (Rhyacotriton cascadae) and Larch Mountain salamander (Plethodon larselli) are restricted to the ecoregion, whereas Cope’s giant salamander (Dicamptodon copei), Van Dyke’s salamander (Plethodon vandykei), and the Cascades frog (Rana cascadae) occur only in the West Cascades and Pacific Coast ecoregions. Of these, the Larch Mountain and Van Dyke’s salamanders and the Cascades
frog are federal Species of Concern. Most of these amphibians are also closely associated with fast-moving, cold mountain streams.
Many large and wide-ranging mammals are declining throughout the West Cascades due to the loss of contiguous suitable habitat or as a result of declining forage. Wide-ranging carnivores including the gray wolf (Canus lupis), grizzly bear (Ursus horribilis), wolverine (Gulo gulo) and lynx (Lynx canadensis) have been extirpated from the ecoregion, while others such as mountain lion (Felix concolor) and black bear (Ursus americanus) persist as apparently stable, self-sustaining populations. Black-tailed deer (Odocoileus heminonus) and elk (Cervus elaphus) populations that expanded during the era of extensive logging are
now declining as most logged areas that provided abundant forage have reforested.
Loss, fragmentation and degradation of aquatic and riparian habitats, and old growth forests have contributed to the decline of a number of species within the ecoregion. Chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), bull trout (Salvelinus confluentus), and steelhead (Oncorhynchus mykiss) are among the well-known aquatic species at-risk within the ecoregion. Substantial efforts have been undertaken to
protect these species.
History & Humans
Less than 0.2% of the West Cascades Ecoregion is under tribal ownership. In Washington, however, much of the ecoregion is within the ceded lands, and usual and accustomed fishing areas of tribes residing in the Puget Trough Ecoregion. Usual and accustomed areas are judicially defined areas where tribal members have fishing rights based on historical use patterns of their tribe. Tribes in Washington manage tribally-owned lands on reservations and are actively involved in research activities on ceded lands. Tribes are active participants in discussions about natural resources management and conservation activities within their usual and accustomed areas.
Outside the Interstate 5 corridor in Washington, the greater Vancouver area, and the lands around Springfield, private timber companies own much of the private land in the West Cascades Ecoregion. Forests have long been the foundation of the local economy in the West Cascades, and decades of logging put the region at the center of controversies over northern spotted owl conservation, logging of old growth forests, and management of federal lands.
Prior to logging, riparian areas had relatively high densities of large conifer trees and were characteristic of late-successional forests of the Pacific Northwest. Timber harvest in streamside areas resulted in a 50% or more loss of the large conifers in many drainages of the West Cascades ecoregion. Although streamside early-successional vegetation such as alders can regenerate relatively quickly, rebuilding the supply of large wood that provides habitat structure and complexity in the streams will require recovery times from decades to
centuries.
Today
Most of the ecoregion’s population is found in small towns in the river valleys where increasing recreational uses supplement the traditional timber-based economy. Land uses range from intensive forestry to municipal supply watersheds to wilderness.
The valleys are also grazed by livestock, used to produce hay and other crops, and are major travel corridors for tourists and commerce. Many towns are increasingly promoting recreational opportunities, including hiking, camping, fishing, hunting, birding, mountain biking and skiing, to supplement timber harvest revenue. However, timber harvest is expected to remain important to local West Cascades economies in the future.
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Links to Completed Ecoregional Assessments
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