Encyclopedia of Earth

Palouse grasslands

Content Cover Image

Hell's Canyon, eastern Washington. Source: Daren H. Spencer

The Palouse grasslands ecoregion extends over eastern Washington, northwestern Idaho and northeastern Oregon. Grasslands and savannas once covered extensive areas of the inter-mountain west, from southwest Canada into western Montana in the USA. Today, areas like the great Palouse prairie of eastern  are virtually eliminated as natural areas due to conversion to rangeland. The Palouse, formerly a vast expanse of native wheatgrasses (Agropyron spp), Idaho Fescue (Festuca idahoensis), and other grasses, has been plowed and converted to wheat fields or is covered by Drooping Brome (Bromus tectorum) and other alien plant species.

caption Palouse Hills east of Walla Walla, virtually all converted to agriculture. Source: Lynn Suckow The Palouse lies in the rain shadow of the Cascades and has a generally semiarid climate. This climate is similar to that of the annual grasslands of California, yet the Palouse historically resembled the mixed-grass vegetation of the Central grasslands, except for the absence of short grasses. Such species as Bluebunch Wheatgrass (Elymus spicatus), Idaho Fescue (Festuca idahoensis) and Giant Wildrye (Elymus condensatus) and the associated species Lassen County Bluegrass (Poa limosa), Crested Hairgrass (Koeleria pyramidata), Bottlebrush Squirrel-tail (Sitanion hystrix), Needle-and-thread (Stipa comata) and Western Wheatgrass (Agropyron smithii) historically dominated the Palouse prairie grassland.

Fire was a  prehistorically major force in shaping the Palouse landscape. For thousands of years, Native Americans set periodic, cool-burning fires that did not damage perennial grasses. Without frequent burning to reduce fuel levels, conditions were ideal for rare but intense fires that destroyed the native perennial species and allowed alien grasses and annual forbs to invade. Excessive grazing also resulted in the demise of many of the perennial grasses. The Columbia River is the principal watercourse draining the Palouse ecoregion.

caption WWF

The Palouse prairie is now intensive agricultural land with patches of shrub-steppe grassland. Once a rich ecosystem year-around, the species that invaded the Palouse following the increase in grazing and the change in fire regime degraded these grasslands to seasonal rangelands.


In addition to the grasses and forbs found in this ecoregion, there are 310 vertebrate species, as well as a host of arthropods and other lifeforms.


caption Yellow-bellied Marmot. Source: C.Michael Hogan Representative mammals found in the Palouse grasslands include the Yellow-bellied Marmot (Marmota flaviventris), found burrowing in grasslands or beneath rocky scree; American Black Bear (Ursus americanus); American Pika (Ochotona princeps); Coast Mole (Scapanus orarius), who consumes chiefly earthworms and insects; Golden-mantled Ground Squirrel (Spermophilus lateralis); Gray Wolf (Canis lupus); Great Basin Pocket Mouse (Perognathus parvus); Northern River Otter (Lontra canadensis); the Near Threatened Washington Ground Squirrel (Spermophilus washingtoni), a taxon who prefers habitat with dense grass cover and deep soils; and the Northern Flying Squirrel (Glaucomys sabrinus), a mammal that can be either arboreal or fossorialan animal that engages in burrowing or living underground.


There are not a large number of amphibians in this ecoregion. The species present are the Great Basin Spadefoot Toad (Spea intermontana), a fossorial toad that sometimes filches the burrows of small mammals; Long-toed Salamander (Ambystoma macrodactylum); Northern Leopard Frog (Glaucomys sabrinus), typically found near permanent water bodies or marsh; Columbia Spotted Frog (Rana luteiventris), usually found near permanent lotic water; Pacific Treefrog (Pseudacris regilla), who deposits eggs on submerged plant stems or the bottom of water bodies; Tiger Salamander (Ambystoma tigrinum), fossorial species found in burrows or under rocks; Woodhouse's Toad (Anaxyrus woodhousii), found in arid grasslands with deep friable soils; Western Toad (Anaxyrus boreas), who uses woody debris or submerged vegetation to protect its egg-masses.


There are a limited number of reptiles found in the Palouse grasslands, namely only: the Northern Alligator Lizard (Elgaria coerulea), often found in screes, rock outcrops as well as riparian vicinity; the Painted Turtle (Chrysemys picta), who prefers lentic Surface waters which are essentially still, such as lakes, ponds or puddles freshwater habitat with a thick mud layer; Yellow-bellied Racer (Chrysemys picta); Ringneck Snake (Diadophis punctatus), often found under loose stones in this ecoregion; Pygmy Short-horned Lizard (Phrynosoma douglasii), a fossorialan animal that engages in burrowing or living underground taxon often found in bunchgrass habitats; Side-blotched Lizard (Uta stansburiana), frequently found in sandy washes with scattered rocks; Southern Alligator Lizard (Elgaria multicarinata), an essentially terrestrial species that prefers riparian areas and other moist habitats; Pacific Pond Turtle (Emys marmorata), a species that usually overwinters in upland habitat; Western Rattlesnake (Crotalus viridis), who, when inactive, may hide under rocks or in animal burrows; Night Snake (Hypsiglena torquata); Western Skink (Plestiodon skiltonianus), who prefers grasslands with rocky areas; Western Terrestrial Garter Snake (Thamnophis elegans), found in rocky grasslands, especially near water; Rubber Boa (Charina bottae).

Biological Distinctiveness

Except for the presence of shrubs, the Palouse grassland resembles the Great Plains shortgrass prairie; however, the once dominant species, Bluebunch Wheatgrass, Idaho fescue, and Bluegrass, are distinctive.

Conservation Status

Habitat Loss and Degradation

Conversion to agriculture has destroyed more than 99 percent of the Palouse grasslands, although damage to this ecoregion actually began with human settlement by Native Americans approximately 13,000 years before present, when hunting of large fauna began here.

Remaining Blocks of Intact Habitat

Only two relatively large blocks of more or less intactThe condition of an ecological habitat being an undisturbed or natural environment habitat remain:

  • Hell’s Canyon National Recreation Area, eastern Washington: 795 square kilometers (km2)
  • Coulee Dam National Recreation Area, eastern Washington: 279 km2

Degree of Fragmentation

The Palouse Grasslands are highly fragmented. Remaining patches of pristine grassland are quite small, with effectively no connectivity in most areas and little core habitat due to ecological edge effects. The individual fragments and clusters that remain are highly isolated, and the intervening landscape precludes dispersal for most taxa.

Degree of Protection

Two protected areas in this ecoregion exceed 500 km2: namely Hell's Canyon and Coulee Dam National Recreation Areas.

Types and Severity of Threats

The Palouse has already suffered from massive conversion to agriculture, with practically the entirety of the habitat already having been converted. Degradation of the remaining fragments continues to be problematic, and there are ongoing moderate levels of wildlife exploitation.

Suite of Priority Activities to Enhance Biodiversity Conservation

Given that nearly all of this ecoregion has already been destroyed, conservation activities are largely futile. Acquisition and preservation of the remaining fragments should nevertheless be a priority, as should restoration of any abandoned agricultural land.

Conservation Partners

  • Idaho Conservation Data Center
  • The Nature Conservancy Of Washington
  • The Nature Conservancy, Western Region
  • The Nature Conservancy of Idaho
  • The Nature Conservancy of Oregon
  • Oregon Natural Heritage Program
  • Washington Natural Heritage Program

Relationship to Other Classification Schemes

Bailey includes the Palouse in the Great Plains-Palouse Dry Steppe Province. Omernik’s Columbia Basin ecoregion extends somewhat further to the west, whereas we classify the area west of the Palouse as part of the Snake/Columbia Shrub Steppe.

Neighboring Ecoregions

The Palouse grasslands has tangent ecoregion boundaries with:


  • D.W.Meinig. 1968. The Great Columbia Plains: A Historical Geography, 1805-1910. University of Seattle Press, Seattle (Revised 1995). ISBN 0-295-97485-0.
  • P.Morgan, S.C. Bunting, A.E. Black, T. Merrill, and S. Barrett. 1996. Fire regimes in the Interior Columbia River Basin: past and present. Final Report, RJVA-INT-94913. Intermountain Fire Sciences Laboratory, USDA Forest Service, Intermountain Research Station, Missoula, Mont.
  • R.F.Noss, E.T. LaRoe III, and J.M. Scott. 1995. Endangered ecosystems of the United States: a preliminary assessment of loss and degradation. U.S. National Biological Service. Biological Report 28.

Disclaimer: This article contains some information that was originally published by the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.




Hogan, C., & Fund, W. (2014). Palouse grasslands. Retrieved from http://www.eoearth.org/view/article/51cbee997896bb431f698fe1


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