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East Cascades Ecoregion: Biodiversity

Map: WA Department of Natural Resources

On the dry side of the Cascades lies one of Washington’s most diverse ecoregions, rich in biological wealth from its montane crest down through open stands of ponderosa pine and Garry oak to the edge of the sagebrush steppe.

Location

The East Cascades ecoregion includes the mountains that lie east of the Cascade crest and the foothills as they flatten into the Columbia Plateau. In Washington, it stretches from roughly Lake Chelan in the north to the Columbia River Gorge in the south. About 10% of the state is found in the ecoregion.

Crossing the Columbia River, the mountainous ecoregion continues south through the length of Oregon.

Roads cross the East Cascades at five points. Through the northern end, Highway 2 connects the Puget Trough with towns like Leavenworth and Wenatchee. Further south, Interstate 90 crosses the Cascades, passing near Roslyn and Cle Elum.

Highway 410 and Highway 12 cross the range and continue west through Mount Rainier National Park. On the southern edge, Highway 14 follows the Columbia River through the towns of Bingen and White Salmon.

Outstanding Biodiversity Features

• High number of rare and endemic plants. The East Cascades ecoregion is home to at least 20 endemic plant species, including the Wenatchee valerian, the Kittitas larkspur, and Thompson’s clover.

• Diverse coniferous forests. These forests include a range of dominant species, from whitebark pine and subalpine fir at high elevations to ponderosa pine parklands lower down.

• Mardon skipper butterflies in southern fescue grasslands. Near the Columbia River Gorge, ponderosa pine savannas carpeted with fescue grass offer prime habitat for the endangered mardon skipper butterfly.

Landforms

Photo: Jim Cummins

The broad U-shaped valleys and steep face of the Cascades’ eastern flank reveal the power of ice age forces. This highland ecoregion averages between 3,000 and 7,000 feet in elevation. Extremes vary from more than 12,000 feet at Mount Adams, an active stratovolcano, to a mere 100 feet above sea level along the Columbia River Gorge.

In the East Cascades ecoregion, the country’s largest granite batholith is found in the Stuart Range. Serpentine soils have evolved from the distinctive geology of the adjoining Wenatchee Mountains. These soils are high in magnesium and low in fertility. They provide habitat for a suite of specially adapted plant species.

Canyons etch the flanks of the East Cascades. These include Tumwater Canyon, which parallels Highway 2, and Hell-Roaring Canyon, which drains the eastern slopes of Mount Adams. These watersheds flow into the great Columbia River.

Near Chelan, the Columbia forms the northeastern edge of ecoregion before the river turns eastward into the Columbia Plateau. The Columbia returns to border Klickitat County along the ecoregion’s southern edge in Washington.

Climate

Eastward from the Cascade crest, the climate dries out dramatically. On the ridgeline more than 120 inches of precipitation falls annually, much of it as snow. At lower elevations, in the rain shadow over the foothills, roughly 20 inches will fall in a year.

Temperatures change as well with the move east. Cold mountain temperatures give way to milder ones at lower elevations. The growing season in the ecoregion ranges from as few as 30 days to as many as 220 days.

Vegetation

Photo: Florence Caplow

The East Cascade ecoregion is one of Washington’s most heavily forested areas. Douglas-fir is found nearly throughout the varied forests.

At the crest, subalpine fir, whitebark pine, Engelmann spruce and mountain hemlock prevail. At mid-elevations, roughly 4,000 to 6,000 feet, forests shift to a mix of western larch and lodgepole pine. Lower yet, ponderosa pine and Douglas-fir forest, with an understory of snowberry and Idaho fescue, is widespread and characteristic.

In the south of the ecoregion, Garry oak woodlands are common in the foothills. The lowest elevations of the East Cascades ecoregion dry out considerably. The ponderosa pine and Douglas-fir forests yield to big sagebrush and bunchgrass, the shrub-steppe vegetation of the Columbia Plateau.

Fire is a powerful force here. Its natural cycles have been disrupted for nearly a century. Fire once swept through dry ponderosa pine forests every 5 to 15 years, clearing away brush and ladder fuels. With management that included fire suppression, that pattern has changed. As a result, less frequent but larger fires have grown common.

Riparian and wetland areas also vary by elevation. In the mountains, coniferous wetlands play an essential role in hydrological cycles. They collect and release snowmelt to the headwaters of streams and rivers.

Lower elevation riversides support lush stands of black cottonwood, alder, and willow. These too are important hydrologically and biologically. They serve as nesting, feeding, and breeding sites for birds and as travel corridors for wildlife.

The moist meadows and talus cliffs of the Wenatchee Mountains shelter a number of endemic plants, such as the Wenatchee checker-mallow and Seely's silene. Priority efforts of the Washington Natural Heritage Program in the East Cascades aim at protecting habitat for rare species like the Wenatchee larkspur and the showy stickseed.

The Columbia River Gorge is another important center for rare plant biodiversity.

Terrestrial Wildlife

Common large mammals in the East Cascades ecoregion include blacktail deer, mule deer, Rocky Mountain elk, black bear, and cougar. Less prevalent are the mountain goat, now only in the north of the ecoregion, and the fisher, now possibly extirpated.

The ecoregion hosts 190 bird species. Northern goshawks, pileated woodpeckers, and Vaux’s swifts utilize the montane forests. The drier pine-oak forest supports the flammulated owl, pygmy nuthatch, and white-headed woodpecker.

Bald and golden eagles are present, but much of their historic range no longer supports them. Peregrine falcons have begun to recover in the ecoregion.

The East Cascades’ rivers and streams support runs of Chinook salmon, coho salmon, and steelhead, though human-mediated environmental changes have greatly reduced their populations. Similarly the range of the bull trout, federally listed as threatened, has diminished. Cutthroat trout and rainbow trout are widespread in ecoregion’s cold waters.

People in the Ecoregion

For at least 11,000 years, tribes from as far as Alaska, California and the Great Plains gathered just east of the Cascades to trade and fish at Celilo Falls. This productive and culturally important fishing site was inundated by the Dalles Dam in 1957.

The eastern flanks of the Cascades have long been inhabited by the Wenatchee, the Chelan, the Kittitas, and the Yakama. Tribes of the region gathered in longhouse communities for the winter and traveled regionally from spring to fall.

People used the Cascades for hunting, fishing, and harvesting plant foods. Camas bulbs and biscuitroot are key ingredients for a traditional bread. Tribes also traveled through the Cascades to visit and trade with neighboring tribes on the west side of the mountains.

Naches Pass in the East Cascades saw the first crossing by a wagon train in the fall of 1853. Settlement along the East Cascade front began about 25 years later.

Farmers in the semi-arid valleys developed their land with irrigation, and the area became well known for its bountiful fruit orchards. The climate also suits vineyards, and that industry has grown in recent years. Grazing and ranching are common land uses as well.

Logging in the East Cascades’ montane forests began more than a century ago and remains an important livelihood.

From the 1880s through the 1930s the northern end of the ecoregion saw a mining boom. The mountains were scoured for gold, copper and coal.

The towns of Roslyn and Cle Elum were coal mining centers. Miners representing over 20 different nationalities worked in the area between 1886 and 1929. The last coal mine closed in 1963.

Along the Columbia River, hydroelectric development made Wenatchee claim itself Washington’s “power belt.”

Today roughly three quarters of the East Cascades ecoregion is publicly owned, much of it by the US Forest Service. Several wilderness areas, including the Alpine Lakes, Norse Peak, Goat Rocks, and Mount Adams, offer protected high elevation habitats for wildlife.

The Yakama Nation, a major landowner, stewards its lands on the eastern slopes of Mount Adams. Washington State manages more than 113,000 acres as well, including the Colockum, Oak Creek, and Chelan Butte Wildlife Areas managed the Department of Fish and Wildlife.

Some two thirds of the area’s important river bottom corridors for anadromous fish are owned privately. This highlights the importance of cooperative public-private efforts, such as the Tieton River Canyon Partnership.

Human Impact

While much of the ecoregion retains natural or semi-natural vegetation, the native biodiversity of the East Cascades ecoregion has been affected by many human activities. Some of the conservation challenges are:

• Habitat loss and fragmentation. The dry ponderosa pine forests, by recent estimates, cover only 1% of their original range. Customary forest management practices, including high grading and selective harvest of big trees, and rural residential development have been among the stresses on these open, park-like stands.

• Altered fire regimes. Larger, less frequent fires are more common now, after nearly a century of fire suppression. Brush and ladder fuels, formerly cleared by low intensity fires every 5 to 15 years, have accumulated. These have both changed forest structure and increased the hazard of catastrophic blazes.

• Recreation impacts. Off-road vehicles, horse traffic, bikers, and hikers can damage fragile soils and introduce invasive species. Snowmobilers and skiers risk disturbing the homes of the few remaining lynx and wolverines.

Within the ecoregion, a number of conservation partnerships are working together to meet these and other biodiversity conservation challenges.

Definitions:

Batholith: A large mass of rock that has melted from pressures within the earth. It cools and then moves into or intrudes other rock formations. >back

Serpentine soil: Soils derived from rocks with very low silica and high magnesium and iron content. The soils are home to a characteristic flora and are often unforested or sparsely forested. >back