More about the Willamette Valley Ecoregion
Bounded on the west by the Coast Range and on the east by the Cascade Mountains, this ecoregion encompasses 5,308 square miles and includes the Willamette Valley and adjacent foothills.
Twenty to 40 miles wide and 120 miles long, the valley is a long, level alluvial plain with scattered groups of low basalt hills. Elevations on the valley floor are about 400 feet at the southern end near Eugene, dropping gently to near sea-level at Portland. The climate is characterized by mild wet winters and warm dry summers. Fertile soil and abundant rainfall make the valley the most important agricultural region in the state.
Culturally, the Willamette Valley is a land of contrasts. Bustling urban areas are nestled within productive farmland. Traditional industries and high technology contribute to the vibrant economy. With Interstate 5 running its length, the Willamette Valley’s economy is shaped by the transportation system and the flow of goods. With nine of the ten largest cities in Oregon, the Willamette Valley is the most urban ecoregion in Oregon. It also is the fastest-growing ecoregion. Pressure on valley ecosystems from population growth, land-use conversion, and pollution is likely to increase.
The Willamette Valley ecoregion is both the fastest growing ecoregion in Oregon and the most densely populated, containing the states’ three largest urban centers (Portland, Salem, Eugene). The population projected for 2050 is approximately four million, nearly double today’s population. The ecoregion also provides about half of the state’s agricultural sales and includes six of the top 10 agricultural-producing counties. Also,16 of top 17 private sector employers (manufacturing, high technology, forest products, agriculture, and services) are located in this ecoregion.
Historical accounts indicate that prior to European settlement, much of the Willamette Valley was covered by native grasses and forbs. The Calapooia people regularly set fires to improve hunting and travel. The fires helped maintain the valley’s mosaic of grasslands, oak savannas, wet prairies and other open habitats. Since the 1850’s, much of the Willamette Valley ecoregion has been altered by development (agricultural or urban), particularly affecting oak woodlands, oak savanna, grassland, riverine, and wetland habitats. The Willamette River has been disconnected from its floodplain, and much of the historic habitats have been fragmented. About 96 percent of the Willamette Valley ecoregion is privately owned, presenting challenges to and opportunities for conservation management.