USDA Natural Resources

Conservation Service

Natural Resources

WASHINGTON STATE DEPARTMENT OF

15 10 5 0 30 60 mi

30 20 10 60 0 120 km

SCALE 1:1 350 000

Universal Transverse Mercator Projection, Zone 10 

Level III ecoregion

Level IV ecoregion

County boundary

State boundary

International boundary

Coastal Lowlands 

Coastal Uplands 

Low Olympics 

Volcanics 

Outwash 

Willapa Hills 

Mid-Coastal Sedimentary 

Southern Oregon Coastal Mountains

Redwood Zone

1a

1b

1c

1d

1e

1f

1g

1h

1i

Fraser Lowland 

Eastern Puget Riverine Lowlands 

San Juan Islands 

Olympic Rainshadow 

Eastern Puget Uplands 

Central Puget Lowland 

Southern Puget Prairies 

Cowlitz/Chehalis Foothills 

Cowlitz/Newaukum Prairie Floodplains

2a

2b

2c

2d

2e

2f

2g

2h

2i

Portland/Vancouver Basin 

Willamette River and Tributaries Gallery Forest 

Prairie Terraces 

Valley Foothills

3a

3b

3c

3d

Western Cascades Lowlands and Valleys 

Western Cascades Montane Highlands 

Cascade Crest Montane Forest 

Cascades Subalpine/Alpine 

High Southern Cascades Montane Forest 

Umpqua Cascades 

Southern Cascades

4a

4b

4c

4d

4e

4f

4g

Yakima Plateau and Slopes 

Grand Fir Mixed Forest 

Oak/Conifer Eastern Cascades Columbia Foothills 

Ponderosa Pine/Bitterbrush Woodland 

Pumice Plateau Forest 

Cold Wet Pumice Plateau Basins 

Klamath/Goose Lake Warm Wet Basins 

Fremont Pine/Fir Forest 

Southern Cascades Slope 

Klamath Juniper/Ponderosa Pine Woodland

9a

9b

9c

9d

9e

9f

9g

9h

9i

9j

North Cascades Lowland Forests

North Cascades Highland Forests

North Cascades Subalpine/Alpine

Pasayten/Sawtooth Highlands

Okanogan Pine/Fir Hills

Chelan Tephra Hills

Wenatchee/Chelan Highlands

Chiwaukum Hills and Lowlands

High Olympics

77a

77b

77c

77d

77e

77f

77g

77h

77i

Rogue/Illinois Valleys

Siskiyou Foothills

Umpqua Interior Foothills

Serpentine Siskiyous

Inland Siskiyous

Coastal Siskiyous

Klamath River Ridges

78a

78b

78c

78d

78e

78f

78g

 1 Coast Range

 2 Puget Lowland

 3 Willamette Valley

 4 Cascades

 9 Eastern Cascades Slopes and Foothills

77 North Cascades

78 Klamath Mountains

PRINCIPAL AUTHORS: David E. Pater (Dynamac Corporation), Sandra A. 

Bryce (Dynamac Corporation), Thor D. Thorson (NRCS), Jimmy Kagan 

(Oregon Natural Heritage Program), Chris Chappell (Washington DNR), James 

M. Omernik (USEPA), Sandra H. Azevedo (OAO Corporation), and Alan J. 

Woods (Dynamac Corporation).

COLLABORATORS AND CONTRIBUTORS: Terry L. Aho (NRCS), Duane 

Lammers (USFS), Thomas Atzet (USFS), Robert Meurisse (USFS), Kenneth 

Radek (USFS), Carl Davis (USFS), Thomas Loveland (USGS), and M. Frances 

Faure (OAO Corporation).

This project was partially supported by funds from the USEPA - Office of 

Research and Development - Regional Applied Research Effort (RARE) 

program.

2 77 1

10

79

15

41

58 16

42

4

9

49

43

46

48

50

3

11

17

59

51

1

12

61

58 16

78

16

60

50 15

17 51

18 47

52 53

17 57

56

62

13

25

67

19

6

5

62

44

21

57

54

7

64

55 70

69

63

27

72

20 40

67

1

26 45 14

71

65

8 28

22

39

66

68

8

73

74

23

63

29

6 38

25

37

36

24

35

23

32

33

75

30

34

32

31

76

 1 Coast Range

 2 Puget Lowland

 3 Willamette Valley

 4 Cascades

 5 Sierra Nevada

 6 Southern and Central California

 Chaparral and Oak Woodlands

 7 Central California Valley

 8 Southern California Mountains

 9 Eastern Cascades Slopes and 

 Foothills

10 Columbia Plateau

11 Blue Mountains

12 Snake River Basin/High Desert

13 Northern Basin and Range

14 Southern Basin and Range

15 Northern Rockies

16 Montana Valley and Foothill

 Prairies

17 Middle Rockies

18 Wyoming Basin

19 Wasatch and Uinta Mountains

20 Colorado Plateaus

21 Southern Rockies

22 Arizona/New Mexico Plateau

23 Arizona/New Mexico Mountains

24 Southern Deserts

25 Western High Plains

26 Southwestern Tablelands

27 Central Great Plains

28 Flint Hills

29 Central Oklahoma/Texas Plains

30 Edwards Plateau

31 Southern Texas Plains

32 Texas Blackland Prairies

33 East Central Texas Plains

34 Western Gulf Coastal Plain

35 South Central Plains

36 Ouachita Mountains

37 Arkansas Valley

38 Boston Mountains

39 Ozark Highlands

40 Central Irregular Plains

41 Canadian Rockies*

42 Northwestern Glaciated Plains

43 Northwestern Great Plains

44 Nebraska Sand Hills

45 Piedmont*

46 Northern Glaciated Plains

47 Western Corn Belt Plains

48 Lake Agassiz Plain

49 Northern Minnesota Wetlands

50 Northern Lakes and Forests

51 North Central Hardwood

 Forests

52 Driftless Area

53 Southeastern Wisconsin Till

 Plains

54 Central Corn Belt Plains

55 Eastern Corn Belt Plains

56 Southern Michigan/Northern Indiana

 Drift Plains

57 Huron/Erie Lake Plains

58 Northeastern Highlands

59 Northeastern Coastal Zone

60 Northern Appalachian Plateau 

 and Uplands

70 Western Allegheny Plateau

71 Interior Plateau

72 Interior River Lowland

73 Mississippi Alluvial Plain

74 Mississippi Valley Loess Plains

75 Southern Coastal Plain

76 Southern Florida Coastal Plain

77 North Cascades*

78 Klamath Mountains*

79 Madrean Archipelago*

*Level III ecoregions identified in the ecoregion revision and subdivision process subsequent to the original map compilations (Omernik 1987).

61 Erie/Ontario Drift and Lake Plain

62 North Central Appalachians

63 Middle Atlantic Coastal Plain

64 Northern Piedmont

65 Southeastern Plains

66 Blue Ridge Mountains

67 Ridge and Valley

68 Southwestern Appalachians

69 Central Appalachians

Level III Ecoregions of the Conterminous United States

12

1h

1b

1a

1g

1d

1b

78f

78d

78e

78a

78b

78b

78c

4f

4g

78d 78g

3d

9g 9h

9e

9f

9f

9g

4e

4d

9i 9g 9j

4c

4b

4a

4c

9d

4b

3c

3c

3d

1d

1b

3b 3d

3c

4b

4a

4d

9a

9b

9b

4d

4b

4a

4b

4c

2h

2h

2i 1d

1b

1f 1b

1e

1d 2g

77i 1c

1b 1d

1a

2f

2f

2d

2b

2e

2e

2f

2e

2a

2b

2e

2e

2c

9a

77h

77f

77g

77b

77b

77c

77b

77b 77a

77g

77c

77a

77b

77e

77d

77d

77c

77e

4b

1f

1b

1a

77b

3d

1d

9c

9b 4a

9c

3a

1d

1d

1b

1a

4d

1g

1i

12

11

11

10

10

1d

4d

4b

9f

4b

4b

1b

1b

1b

78a

9h

9b

1a

77c

9g

9g

3b

3c

3c

3c

15

77c

77c

4b

2d

Salem

Victoria

Olympia

Bellingham

Bend

Eugene

Medford

Portland

Roseburg

Seattle

Wenatchee 

Albany

Astoria

Cathlamet

Chehalis

Coquille

Corvallis

Dallas

Ellensburg

Everett

Gold

Beach

Goldendale

Grants Pass

Hillsboro

Hood River

Kelso

Klamath Falls Lakeview

Madras

McMinnville

Aberdeen

Mount 

 Vernon

Newport

Okanogan

Oregon

Port Angeles

Prineville

Saint 

Helens

South Bend

Stevenson

Tacoma

The Dalles

Tillamook

Vancouver

Yakima

Brookings

City

Coos

Bay

Wenatchee

Chelan

Ross 

Lake

Lake 

Lake

Harbor

Grays

Summer

Lake 

Abert

Goose 

 Lake

Lake

Crater 

 Lake

Crescent

Waldo

Lake

Detroit 

Lake

Green Peter 

Crane Prairie

Wickiup

Reservoir

Lake

Lake

Reservoir

Chinook

Lake

Hills

Creek

Lake

Fern

Ridge

Lake

Alder Lake

Cle Elum

Lake

 Strait of 

Juan de Fuca

Klamath

Upper

Lake

Willapa

Bay

Sprague River

Klamath River

Illinois River

R ogu eRiver

Umpqua River

Deschutes River

Crooked River

Santiam River

South Santiam River

Clackamas River

Deschutes Rive r Columbia River

Klickitat River

Cispus River Cowlitz River

Yakima River

Puyallup River

Nisqually River

Puget So

u

n

d

G reen River

Snoqualmie River

Columbia Ri v e r

Skykomish River

Skagit River

Wenatchee River

Quinault River

Chehalis River

John Day River

Queets River

Chewack River

P

a

c

i

f

i

c

O

c

e

a

n

Sol Duc

River

Hoh River

Willamette

River

CANADA

UNITED STATES

O R E G O

W A

N

S H I N G T O N

BRITISH COLUMBIA

WASHINGTON

OREGON

CALIFORNIA NEV.

124° 123° 122° 121° 120°

124° 123° 122° 121° 120°

42°

43°

44°

45°

46°

47°

48°

49°

42°

43°

44°

45°

46°

47°

48°

49°

1. Coast Range

Highly productive, rain-drenched coniferous forests cover the low mountains of the Coast Range. Sitka spruce forests originally dominated the fog-shrouded coast, while a mosaic of western red cedar, western hemlock, and seral 

Douglas-fir blanketed inland areas. Today Douglas-fir plantations are prevalent on the intensively logged and managed landscape.

The Coastal Lowlands ecoregion encompasses estuarine marshes, freshwater lakes, black-water streams, 

marine terraces, and sand dune areas. Elevations range from sea level to 300 feet. Channelization and 

diking have converted many of its wetlands into dairy pastures; associated stream quality degradation has 

occurred. 

The Coastal Uplands ecoregion extends to an elevation of about 500 feet. The climate of Ecoregion 1b is 

marine-influenced with an extended winter rainy season, enough fog during the summer dry season to 

reduce vegetal moisture stress, and a lack of seasonal temperature extremes. The ecoregion roughly corresponds 

with the historic distribution of Sitka spruce. The extent of the original forest has been greatly reduced by 

logging. 

The Low Olympics ecoregion contains foothills and mountains and rises to an elevation of approximately 

4000 feet. Copious precipitation (up to 200 inches/year) supports a lush, epiphyte-rich rainforest of 

western hemlock, western red cedar, and Douglas-fir. Much of the region is in the third rotation of logging. 

However, a portion of the region lies within the Olympic National Park and contains ancient forests.

The Volcanics ecoregion varies in elevation from 1000 to 4000 feet and is disjunct. Columnar and 

pillow basalt outcrops occur. Its mountains may have been offshore seamounts engulfed by continental 

sediments about 200 million years ago. The basaltic substrate preserves relatively stable summer stream flows 

that still support spring chinook salmon and summer steelhead. Its forests are intensively managed.

The Outwash ecoregion is a gently sloping fan of glacial outwash material that is dominated by 

industrial timber plantations. It lies outside the zone of marine influence and has lower stream flows 

than most other parts of the Coast Range (1). 

The Willapa Hills ecoregion has erodible silt and clay soils. Drainage density is lower than in other 

parts of the Coast Range (1) that are also underlain by sedimentary rock. Industrial timberland has 

almost completely replaced the historic forests of the ecoregion.

The Mid-Coastal Sedimentary ecoregion is commonly underlain by massive beds of siltstone and 

sandstone. Its dissected, forested mountains are more rugged than in Ecoregion 1f and are prone to mass 

movement when the vegetal cover is removed. Stream gradients and fluvial erosion rates can be high. 

The Southern Oregon Coastal Mountains is a mountainous ecoregion with an ocean-modified climate. 

It is a transitional area between the Siskiyou Mountains and the Coast Range and is underlain by Jurassic 

sandstone, metamorphosed sediments, granite, and serpentine. Overall, the geology of Ecoregion 1h is complex, 

like that of the Siskiyou Mountains, but its mountains are lower and are not as dissected. The distributions of 

northern and southern vegetation blend together here and species diversity is high.

The Redwood Zone is the northernmost tip of an ecoregion that extends to San Francisco Bay. 

Remnants of unlogged redwood forest survive east of Brookings. The redwood forest, when it 

functioned as an intact ecosystem, moderated its own microclimate by entrapment of coastal fog and by shading.

2. Puget Lowland

This broad rolling lowland is characterized by a mild maritime climate and flanks the intricately cut coastline of Puget Sound. It occupies a continental glacial trough and has many islands, peninsulas, and bays. Coniferous forest 

originally grew on the ecoregion’s ground moraines, outwash plains, floodplains, and terraces. The distribution of forest species is affected by the rainshadow from the Olympic Mountains.

The Fraser Lowland ecoregion is composed of glacial drift plains, terraces, and some floodplains. 

Undulating terrain, a mild, wet climate, and productive pastureland are characteristic. This ecoregion has 

the highest dairy farm concentration in Washington. 

The Eastern Puget Riverine Lowlands ecoregion is composed of floodplains and terraces. Western red 

cedar forest, western hemlock forest, and both riverine and wetland habitat were common before the 19th 

century. Subsequently, many of the wetlands were drained. Pastures, cropland, forests, and urban centers now 

dominate the landscape. 

The glacial-scoured San Juan Islands ecoregion is underlain by sedimentary rock. Well-drained, shallow 

soils are typical. It is in the rainshadow of the Olympic Mountains. The driest vegetation types in the 

Puget Lowland (2) grow here and include Douglas-fir/grand fir forests, oak woodlands, and grasslands. 

The Olympic Rainshadow ecoregion receives, on the average, only 10 to 40 inches of precipitation each 

year depending on location. Streams on the till plains have low discharge, and their drainage pattern is 

often deranged or internal. Its loamy soils tend to retain moisture better than the soils of the San Juan Islands (2c) 

and support pastureland, cropland, and woodland.

The Eastern Puget Uplands ecoregion is made up of rolling moraines and foothills and is a zone of 

transition. Both Puget Lowland and Cascadian vegetation associations occur with the latter most common 

in areas of greatest elevation and precipitation. The relief and precipitation of Ecoregion 2e tend to be high for 

the Puget Lowland (2), but low compared to the Cascades (4) or the North Cascades (77). 

The Central Puget Lowland ecoregion is the heart of Puget Sound both in physical and human terms. 

Its undulating drift plains are heavily urbanized in the east and more rural and forested in the west. 

Well-drained, gravelly soils are common and exhibit limited moisture holding capacity and rather low 

agricultural productivity.

The Southern Puget Prairies ecoregion is comprised of nearly level to rolling glacial outwash plains 

and ground moraines. Well-drained soils promote a land cover mosaic of Douglas-fir/western hemlock 

forests, prairies, oak woodlands, cropland, and pastureland. 

The Cowlitz/Chehalis Foothills are rolling to steeply sloping. The potential natural vegetation, western 

hemlock and western red cedar forest, is similar to Ecoregions 2a, b, d, e, f, and i. However, in contrast 

to much of the Puget Lowland (2), Ecoregion 2h was unaffected by continental glaciation. 

The Cowlitz/Newaukum Prairie Floodplains ecoregion is a transitional zone between the Puget 

Lowland (2) and the Willamette Valley (3). Its vegetation, soil, and climate are similar to those of the 

Southern Puget Prairies (2g) and the Eastern Puget Riverine Lowlands (2b). However, unlike those areas, it did 

not experience continental glaciation.

3. Willamette Valley

Rolling prairies, deciduous/coniferous forests, and extensive wetlands characterized the pre-settlement landscape of this broad, lowland valley. Ecoregion 3 is distinguished from the adjacent Coast Range (1) and Cascades (4) by 

lower precipitation, less relief, and a different mosaic of vegetation. Landforms consist of terraces and floodplains, interlaced and surrounded by rolling hills. Productive soils and a temperate climate make it one of the most 

important agricultural areas in Oregon.

The Portland/Vancouver Basin ecoregion is composed of undulating terraces and floodplains with 

numerous wetlands, oxbow lakes, and ponds. Historically, prairie and oak woodland grew on better 

drained sites while wetlands, Oregon ash, and Douglas-fir occurred elsewhere in the fault block basin. Today, 

Ecoregion 3a is dominated by urban and suburban development, pastures, and nurseries. Weather here is often 

affected by cold or warm easterly winds that blow through the Columbia River Gorge.

In the Willamette River and Tributaries Gallery Forest ecoregion, meandering, low-gradient channels 

and oxbow lakes are incised into broad floodplains. Deciduous riparian forests that once grew on its 

fertile, alluvial soils have been largely replaced by agriculture and rural residential, suburban, and urban 

The undulating Prairie Terraces ecoregion is dissected by low-gradient, meandering streams and rivers. 

Its fluvial terraces once supported prairie and oak woodlands which were maintained by burning; 

Oregon ash and Douglas-fir occurred in wetter areas. Today, grass seed and grain crops are commonly grown. 

The Valley Foothills ecoregion is a transitional zone between the Willamette Valley (3), the Cascades 

(4), and the Coast Range (1). It has less rainfall than adjacent, more mountainous ecoregions and, 

consequently, its potential natural vegetation is distinct. Oregon white oak and Douglas-fir were originally 

dominant but, today, rural residential development, woodland, pastureland, vineyards, tree farms, and orchards 

4. Cascades

This mountainous ecoregion underlain by Cenozoic volcanics has been affected by alpine glaciations. It is characterized by steep ridges and river valleys in the west, a high plateau in the east, and both active and dormant 

volcanoes. Elevations range upwards to 14410 feet. Its moist, temperate climate supports an extensive and highly productive coniferous forest. Subalpine meadows occur at high elevations.

The Western Cascades Lowlands and Valleys ecoregion is characterized by a network of steep ridges 

and narrow valleys. Elevations are generally less than 3200 feet and are the lowest in Ecoregion 4. The 

wet, mild climate promotes lush forests that are dominated by Douglas-fir and western hemlock. It is one of the 

most important timber producing areas in the Northwest.

The Western Cascades Montane Highlands ecoregion is composed of steep, glaciated mountains that 

have been dissected by high-gradient streams. It has lower temperatures than Ecoregion 4a and is 

characterized by a deep annual snow pack. Soils are of the frigid and cryic temperature regimes and support 

forests dominated by Pacific silver fir, western hemlock, mountain hemlock, Douglas-fir, and noble fir.

The Cascade Crest Montane Forest ecoregion consists of an undulating plateau punctuated by volcanic 

buttes and cones that reach a maximum elevation of about 6500 feet. Its Pliocene and Pleistocene 

volcanics were glaciated leaving numerous lakes in their wake. The ecoregion is extensively forested with 

mountain hemlock and Pacific silver fir.

The Cascades Subalpine/Alpine ecoregion is an area of high, glaciated, volcanic peaks that rise above 

subalpine meadows. Elevations range from 5600 to 12000 feet. Active glaciation occurs on the highest 

volcanoes and decreases from north to south. The winters are very cold and the growing season is extremely 

short. Flora and fauna adapted to high elevations include herbaceous and shrubby subalpine meadow vegetation 

and scattered patches of mountain hemlock, subalpine fir, and whitebark pine.

The High Southern Cascades Montane Forest ecoregion consists of an undulating, glaciated plateau 

punctuated by volcanic buttes and cones. Maximum elevation is about 7000 feet. Its mixed coniferous 

forest is dominated by mountain hemlock and Pacific silver fir. Grand fir, white fir, Shasta red fir, and lodgepole 

pine also occur and increase to the south and east. Ecoregion 4e tends to be drier than Ecoregion 4c and has 

longer periods of summer drought and more intermittent streams.

The Umpqua Cascades ecoregion is a transitional zone between the lusher and moister forests of 

Ecoregions 4a and 4b to the north and the drier forests of the Southern Cascades (4g) and the Klamath 

Mountains (78). Vegetation is a mix of grand fir, white fir, western hemlock, Pacific silver fir, and Douglas-fir 

with Shasta red fir also occurring and increasing to the south. Vegetation diversity is greater than in Ecoregions 

4a and 4b which have cooler summers.

The Southern Cascades ecoregion is drier than others in the Cascades (4). It is characterized by gently 

sloping mountains, broad valleys, a long summer drought, and high vegetation diversity. White fir is 

common; at low elevations, Douglas-fir and ponderosa pine become prevalent and, at high elevations, Shasta red 

fir occurs.

The unglaciated Yakima Plateau and Slopes ecoregion is characterized by plateaus, buttes, and canyons, 

a dry continental climate, and open woodlands dominated by ponderosa pine. Fire is an integral part of its 

ecosystem.

The Grand Fir Mixed Forest ecoregion is mostly outside the limit of maritime climatic influence. It is 

characterized by high, glaciated plateaus and mountains, frigid soils, and a snow-dominated, continental 

climate. The vegetation is a mix of grand fir, Douglas-fir, and ponderosa pine.

The Oak/Conifer Eastern Cascades Columbia Foothills ecoregion is more diverse than any other 

within the Eastern Cascade Slopes and Foothills (9). Soil, climate, and landforms are all highly variable 

and contribute to a mosaic of vegetation types that includes grasslands, oak woodlands, Douglas-fir/ponderosa 

pine forests, and western hemlock/Douglas-fir forests. Maritime weather systems sometime enter Ecoregion 9c 

via the Columbia River Gorge and moderate its otherwise continental climate. 

The Ponderosa Pine/Bitterbrush Woodland ecoregion has a terrain dominated by undulating volcanic 

plateaus and canyons. Its well-drained, frigid soils are often derived from ash and support nearly 

homogenous stands of ponderosa pine. Bitterbrush grows at lower elevations. Stands of lodgepole pines are 

largely absent in contrast to the Pumice Plateau Forest (9e) to the south.

The Pumice Plateau Forest ecoregion is a high volcanic plateau that is thickly covered by Mt. Mazama 

ash and pumice. Its residual soils are somewhat excessively drained. Spring-fed creeks, marshes, and a 

few lakes occur. Forests of ponderosa pine are common on slopes; colder depressions and flats are dominated by 

The Cold Wet Pumice Plateau Basins ecoregion includes Sycan Marsh, Klamath Marsh, and La Pine 

Basin. All three areas function as cold air catch-basins during the winter and have lower minimum 

temperatures than Ecoregion 9e. Its marshes and forested wetlands are commonly 4500 to 5000 feet in elevation 

and are important habitat for migratory waterfowl. The La Pine Basin is underlain by thick lacustrine deposits 

that exhibit high ground water levels during the spring snow melt.

The Klamath/Goose Lake Warm Wet Basins ecoregion is drier than elsewhere in Ecoregion 9, yet it 

contains floodplains, terraces, and a pluvial lake basin. Its tule, sedge, and cattail wetlands have largely 

been drained for agriculture. Sagebrush and bunchgrass occur in upland areas.

The terrain of the Fremont Pine/Fir Forest ecoregion is composed of mountains and high plateaus. Its 

continental climate and diverse terrain support a range of vegetation types. Ponderosa pine woodlands 

are common at lower elevations while white fir is more prevalent in higher areas.

The Southern Cascades Slope ecoregion is a transitional zone between the Cascades (4) and the drier 

Eastern Cascade Slopes and Foothills (9). Forests of ponderosa pine blanket the mountainous landscape; 

white fir, Shasta red fir, and Douglas-fir grow at higher elevations. Much of Ecoregion 9i typically receives 

more precipitation than Ecoregions 9a, c, d, e, f, g, and j.

The terrain of the Klamath Juniper/Ponderosa Pine Woodland ecoregion consists of undulating hills, 

escarpments, and plateaus. Mean annual precipitation ranges from 12 to 20 inches per year. Reservoirs 

dot the landscape and are important to lowland irrigation. The natural vegetation was mostly juniper in the 

south and a mix of ponderosa pine and juniper in the north; today, a mosaic of pastures and woodland occurs.

9. Eastern Cascades Slopes and Foothills

Ecoregion 9 is in the rainshadow of the Cascade Mountains. Its climate exhibits greater temperature extremes and less precipitation than ecoregions to the west. Open forests of ponderosa pine and some lodgepole pine distinguish 

this region from the higher ecoregions to the west where hemlock and fir forests are common, and the lower, dryer ecoregions to the east where shrubs and grasslands are predominant. The vegetation is adapted to the prevailing 

dry, continental climate and is highly susceptible to wildfire. Volcanic cones and buttes are common in much of the region.

77. North Cascades

The terrain of Ecoregion 77 is composed of high, rugged mountains. It contains the greatest concentration of active alpine glaciers in the conterminous United States and has a variety of climatic zones. A dry continental climate 

occurs in the east and mild, maritime, rainforest conditions are found in the west. It is underlain by sedimentary and metamorphic rock in contrast to the adjoining Cascades (4) which are composed of volcanics.

The North Cascades Lowland Forests ecoregion is composed of low mountains, broad glaciated valleys, 

and glacial-fed rivers that receive, on average, 60 to 90 inches of precipitation per year. Extensive, 

productive rainforests have developed under the mild maritime climate and are dominated by western hemlock, 

Douglas-fir, and western red cedar. Pastures occur in the valleys.

 The landscape of the North Cascades Highland Forests ecoregion consists of steep, glaciated ridges, 

high-gradient streams, and tarns. Colder climatic conditions, deeper snow pack, and Pacific silver 

fir/mountain hemlock forests distinguish it from Ecoregion 77a. 

 The North Cascades Subalpine/Alpine ecoregion is characterized by high mountain peaks, bare rock, 

glaciers, many tarns, plentiful precipitation, and sediment-laden glacial meltwater streams. Subalpine 

meadows occur around the taller peaks; their flora and fauna is adapted to the prevailing subarctic climate.

The Pasayten/Sawtooth Highlands has colder winter temperatures than elsewhere in Ecoregion 77 and has 

experienced both continental and alpine glaciation. Its landscape of high ridges, plateaus, and trough valleys 

is dominated by subalpine fir. In addition, lodgepole pine grows in the northeast, Douglas-fir is found at lower 

elevations, and many wetlands occur. Mean precipitation is from 25 to 65 inches per year and varies according to 

elevation and slope aspect; it is less than that received by Ecoregions 77a, b, c, and i which occur to the west.

The glaciated Okanogan Pine/Fir Hills ecoregion has rounded mountains and broad, U-shaped valleys. 

Elevations are lower and slope angles are gentler than further west in the jagged, mountainous areas of the 

North Cascades (77). Precipitation ranges from 10 to 35 inches per year, falling mostly as snow. It is lower than 

elsewhere in Ecoregion 77 and droughty conditions prevail. Precipitation and temperature both vary

according to elevation, microtopography, and slope aspect and affect the distribution of vegetation. Ponderosa 

pine grows in lower, drier areas and Douglas-fir is found at higher elevations. Bluebunch wheatgrass is 

common in the understory of the south and Idaho fescue grows in the north. 

The steep, glaciated Chelan Tephra Hills ecoregion is dominated by deep deposits of coarse, volcanic 

ejecta which contribute to the character of this dry, east-side region. Elevations range from 1200 to 

5700 feet. Ponderosa pine grows in lower areas, Douglas-fir occurs in the mid-elevations, and subalpine fir is 

found above 5000 feet in elevation.

The glaciated Wenatchee/Chelan Highlands ecoregion is characterized by mountains and ridges, tarns, 

U-shaped valleys, and dissected high-gradient streams. Leeward climatic conditions prevail. Douglasfir, grand fir, and subalpine fir are common; lodgepole pine and Englemann spruce also occur. Average 

precipitation ranges from only 15 to about 40 inches per year.

The Chiwaukum Hills and Lowlands are composed of feldspar-rich sandstone and are unlike 

neighboring ecoregions which are underlain by metamorphic and igneous rock. Its low mountains, hills, 

and cuestas can be highly erodible and unstable. Streams have high sediment yields and run in V-shaped 

valleys; their network forms a trellis pattern.

The High Olympics ecoregion contains steep, glaciated mountains that reach an elevation of 8000 feet. 

It is characterized by rock outcrops, tarns, persistent snow pack, alpine glaciers, and high-gradient, 

glacial-fed streams. Its vegetation includes subalpine mountain hemlock and Pacific silver fir forests as well as 

alpine meadows. Subalpine fir occurs on the xeric soils of northeastern rainshadow areas.

78. Klamath Mountains 

The ecoregion is physically and biologically diverse. Highly dissected, folded mountains, foothills, terraces, and floodplains occur and are underlain by igneous, sedimentary, and some metamorphic rock. The mild, subhumid 

climate of Ecoregion 78 is characterized by a lengthy summer drought. It supports a vegetal mix of northern Californian and Pacific Northwest conifers.

The mountainous Serpentine Siskiyous ecoregion is highly dissected and is underlain by Jurassic 

serpentine. Rare understory species and sparse woodlands grow on its unique soils. Mining and 

associated water quality problems occur.

The Inland Siskiyous ecoregion is mountainous. Granitic and sedimentary rock underlie the ecoregion 

and distinguish it from the volcanic mountains of the Cascades (4). Greater fire frequency, less annual 

precipitation, longer summer droughts, and a lack of tanoak differentiate it from the Coastal Siskiyous (78f).

The Coastal Siskiyous ecoregion has a wetter and a milder maritime climate than elsewhere in the 

Klamath Mountains (78). Productive forests composed of tanoak, Douglas-fir, and some Port Orford 

cedar cover the dissected, mountainous landscape.

The Klamath River Ridges ecoregion has a dry, continental climate and receives, on average, 25 to 35 

inches of rain annually. Low elevation and south-facing sites have a more drought resistant vegetation 

than elsewhere in the Klamath Mountains (78) such as juniper, chaparral, and ponderosa pine. Higher areas and 

north-facing slopes are covered by Douglas-fir, white fir, and Shasta red fir. Ecoregion 78g has less 

precipitation, more sunny days, and a greater number of cold, clear nights than the Inland Siskiyous (78e).

The Rogue/Illinois Valleys ecoregion consists of floodplains and terraces that have a local relief of 100 to 

600 feet. It is characterized by hot, dry summers and a native vegetation of Oregon white oak, madrone, 

California black oak, ponderosa pine, and grasslands. Today, a mix of orchards, cropland, pastureland, oak 

woodland, pine woodland, and rural residential development occurs. Vegetation and land use are more similar to 

those of northern California’s inland valleys than to those of the Willamette Valley (3).

The Siskiyou Foothills are affected by a Mediterranean climate that is similar to Ecoregion 78a. The 

driest area occurs east of Medford and is dominated by oak woodlands, ponderosa pine, and Douglas-fir. 

The wetter foothills adjacent to the Illinois Valley support Douglas-fir, madrone, and incense cedar.

The Umpqua Interior Foothills ecoregion is an intermingling of narrow valleys, terraces, and foothills. 

It contrasts with the terrain of the more mountainous Inland Siskiyous (78e). A mix of oak woodlands, 

Douglas-fir, ponderosa pine, and madrone intermingle with pastureland, vineyards, orchards, and row crops. The 

vegetation and land use are similar to those of Ecoregions 78a and 78b. Summers are hot and dry and, although 

the climate is transitional to both the Willamette and Rogue valleys, it is most similar to the Rogue Valley.

1a

1b

1c

1d

1e

1f

1g

1h

1i

2a

2b

2c

2d

2e

2f 

2g

2h

2i

3b

3c

3d

3a 

4a

4b

4c

4d

4e

4f

4g

9f

9g

9h

9i

9j

9a

9c

9d

9b

9e

77a

77b

77c

77d

77e

77f

77g

77h

77i

78a

78b

78c

78d

78e

78f

78g

Much of the Coast Range (1) has been altered by intensive forest management.

The Coastal Lowlands (1a) are noted for their 

rich pastures. Dairy farming is common.

Chinook and coho salmon are a common sight 

during their spawning seasons in the high 

quality coastal rivers of Ecoregion 1.

Historically, land use in the Coast Range (1) 

has been dominated by logging. 

The Olympic Mountains cast a rainshadow over Ecoregions 2c and 2d. The driest vegetation 

types in the Puget Lowland (2) are found in this rainshadow and include Douglas-fir/grand fir 

forests, oak woodlands, and grasslands.

A landscape mosaic of coniferous forest and 

prairie characterize the Southern Puget 

Prairies (2g).

Western sandpipers and many other shorebirds 

are found within the Puget Lowland (2).

Extensive urbanization in the Central Puget 

Lowland (2f) has affected the environment.

The agricultural patchwork of the Willamette Valley (3).

Canada geese and other migratory waterfowl 

species are common in the Willamette Valley 

(3).

A mosaic of rural residential development, 

pastureland, woodland (dominated by Oregon 

white oak and Douglas-fir), and vineyards 

occur in the Valley Foothills (3d).

Mount Jefferson and subalpine meadows are typical of the landscapes around the tall volcanic 

peaks of Ecoregion 4d.

Remnants of old-growth western hemlock and 

western red cedar forests occur in Ecoregion 4a. 

Northern spotted owls are found here.

Intensive forestry is a common sight in 

Ecoregions 4a and 4b.

High gradient cascading streams are common in 

Ecoregion 4b and at higher elevations in 

Ecoregion 4a.

The landscape of Ecoregions 4c and 4e is 

dominated by a high forested volcanic plateau 

dotted with glacial lakes.

Homogenous forests of ponderosa pine and lodgepole pine are common in Ecoregion 9e.

Mule deer are found throughout the Eastern 

Cascades Slopes and Foothills (9).

Coarse, deep, 

pumice-derived 

soils are a 

feature of the 

Pumice Plateau 

Forest (9e).

Forests of ponderosa pine are prevalent 

throughout most of the Eastern Cascades Slopes 

and Foothills (9).

Ecoregion 9g is drier than others in the 

Eastern Cascades Slopes and Foothills (9). Its 

agricultural landscape is intensively irrigated.

The Picket Range is an excellent example of the jagged, glaciated peaks that dominate the 

higher elevations of the North Cascades (77). Extensive, productive coniferous forests 

cover the low mountains of Ecoregion 77a.

Gray, sediment laden, glacial streams are 

common in Ecoregions 77a and 77b.

Mountain goats are a common sight in the North 

Cascades Subalpine/Alpine ecoregion (77c).

Dry vegetation types occur in the rainshadow of 

the North Cascades Mountains that experience 

a high fire frequency.

Dry oak woodlands are 

common in the rolling 

foothills of Ecoregion 78b.

The landscape of the Inland Siskiyous (78e) is characterized by highly dissected mountains that 

are blanketed by a variety of vegetation types.

Summer drought affects the valley and foothills 

of Ecoregion 78c.

Rare understory species 

and sparse vegetation 

grow on soils derived 

from serpentine in 

Ecoregion 78d.

Tailings from past and present mining 

activities continue to impact water quality and 

stream habitat in the mountainous areas of the 

Klamath Mountains (78).

INTERIOR—GEOLOGICAL SURVEY, RESTON, VIRGINIA—1998

Literature Cited:

Bailey, R.G., Avers, P.E., King, T., and McNab, W.H., eds., 1994, Ecoregions and subregions of the United 

States (map) (supplementary table of map unit descriptions compiled and edited by McNab, W.H. and Bailey, 

R.G.): Washington, D.C., U.S. Department of Agriculture - Forest Service, scale 1:7,500,000.

Gallant, A.L., Whittier, T.R., Larsen, D.P., Omernik, J.M., and Hughes, R.M., 1989, Regionalization as a tool for 

managing environmental resources: Corvallis, Oregon, U.S. Environmental Protection Agency EPA/600/3-

89/060, 152 p.

Griffith, G.E., Omernik, J.M., Wilton, T.F., and Pierson, S.M., 1994, Ecoregions and subregions of Iowa - a 

framework for water quality assessment and management: The Journal of the Iowa Academy of Science, v. 

101, no. 1, p. 5-13. 

Omernik, J.M., 1987, Ecoregions of the conterminous United States (map supplement): Annals of the Association 

of American Geographers, v. 77, no. 1, p. 118-125, scale 1:7,500,000.

Omernik, J.M., 1995, Ecoregions - a framework for environmental management, in Davis, W.S. and Simon, T.P., 

eds., Biological assessment and criteria - tools for water resource planning and decision making: Boca Raton, 

Florida, Lewis Publishers, p. 49-62.

U.S. Department of Agriculture - Soil Conservation Service, 1981, Land resource regions and major land resource 

areas of the United States: Agriculture Handbook 296, 156 p.

U.S. Environmental Protection Agency, 1996, Level III ecoregions of the continental United States (revision of 

Omernik, 1987): Corvallis, Oregon, U.S. Environmental Protection Agency - National Health and 

Environmental Effects Research Laboratory Map M-1, various scales.

Wiken, E., 1986, Terrestrial ecozones of Canada: Ottawa, Environment Canada, Ecological Land Classification 

Series no. 19, 26 p.

Ecoregions denote areas of general similarity in ecosystems and in the type, quality, 

and quantity of environmental resources; they are designed to serve as a spatial 

framework for the research, assessment, management, and monitoring of ecosystems 

and ecosystem components. Ecoregions are directly applicable to the immediate needs 

of state agencies, including the development of biological criteria and water quality 

standards, and the establishment of management goals for nonpoint-source pollution. 

They are also relevant to integrated ecosystem management, an ultimate goal of most 

federal and state resource management agencies.

The approach used to compile this map is based on the premise that ecological regions 

can be identified through the analysis of the patterns and the composition of biotic and 

abiotic phenomena that reflect differences in ecosystem quality and integrity (Wiken, 

1986; Omernik, 1987, 1995). These phenomena include geology, physiography, 

vegetation, climate, soils, land use, wildlife, and hydrology. The relative importance of 

each characteristic varies from one ecological region to another regardless of the 

hierarchical level. A Roman numeral hierarchical scheme has been adopted for 

different levels of ecological regions. Level I is the coarsest level, dividing North 

America into 15 ecological regions, with level II dividing the continent into 51 regions. 

At level III, the continental United States contains 98 regions (United States 

Environmental Protection Agency [USEPA], 1996). Level IV is a further subdivision 

of level III ecoregions. Explanations of the methods used to define the USEPA’s 

ecoregions are given in Omernik (1995), Griffith and others (1994), and Gallant and 

others (1989).

This level III and IV ecoregion map was compiled at a scale of 1:250,000; it depicts 

revisions and subdivisions of earlier level III ecoregions that were originally compiled at 

a smaller scale (USEPA, 1996; Omernik, 1987). This poster is the product of a 

collaborative effort primarily between the USEPA Region X, the USEPA National 

Health and Environmental Effects Research Laboratory (Corvallis, Oregon), the Oregon 

Natural Heritage Program, the United States Department of Agriculture - Forest Service 

(USFS), the United States Department of Agriculture - Natural Resources Conservation 

Service (NRCS) (formerly the Soil Conservation Service), the United States Department 

of the Interior - Geological Survey (USGS) - Earth Resources Observation Systems 

(EROS) Data Center, the Washington State Department of Natural Resources 

(Washington DNR), and the Washington State Department of Ecology. 

 

This project is associated with an interagency effort to develop a common framework of 

ecological regions. Reaching that objective requires recognition of the differences in the 

conceptual approaches and mapping methodologies that have been used to develop the 

most commonly used existing ecoregion-type frameworks, including those developed by 

the USFS (Bailey and others, 1994), the USEPA (Omernik, 1987, 1995), and the NRCS 

(United States Department of Agriculture - Soil Conservation Service, 1981). As each 

of these frameworks is further developed, the differences between them are becoming 

less. Regional collaborative projects such as this one in Washington and Oregon, where 

agreement can be reached among multiple resource management agencies, is a step in 

the direction of attaining commonality and consistency in ecoregion frameworks for the 

entire nation.

Ecoregions of Western Washington and Oregon