Willamette Valley Prairies

History and importance of Willamette Valley prairies

Prairies were once widespread in Oregon's Willamette Valley. Many of these sites could support forest vegetation, but remained open prairie because of prescribed burning by the native Kalapuya, who lived in the region for perhaps 10,000 years. The Kalapuya burned in the Valley during the late summer to increase growth of food plants and improve hunting. Frequent burning reduced the abundance of shrubs and trees, favoring an open prairie with a rich variety of native herbaceous plants and animals.


Willamette Valley in 1840sAfter Euro-American settlement in the 1830s, regular burning of prairies ceased and most of the Valley was gradually developed for agricultural or urban uses. Woody species and non-native herbaceous weeds invaded remaining natural areas. As a result, native prairies now cover much less than 1% of their former area, making them among the rarest of North American ecosystems. The decline in native prairies and their increased fragmentation has led to the decline of many native prairie plants and animals. Even so, remnants of these highly diverse and complex ecosystems provide necessary habitat for many rare species.

As important as Willamette Valley prairies are, they have been under-studied. This is changing, however. Recent research on prairie ecology, conservation biology, restoration and management is helping both scientists and managers understand and appreciate these fascinating ecosystems.


2001 Mark V. Wilson and Oregon State University