Ecoregion Unit Descriptions
This Ecodomain covers the southern interior plateau and is an extension of the dry climate regime that occupies the interior of northern Mexico and the northwestern United States. Its two most commonly recognized climates are arid desert (south of Oregon and Idaho) and semiarid steppe (north of Nevada and Utah into British Coumbia) . In British Columbia this Ecodomain is represented by only one ecodivision.
Semi-Arid Steppe Highland Ecodivision
Southern Interior Ecoprovince
This Ecodivision occurs within the Dry Ecodomain in southern British Columbia and includes the leeward ranges of the Coast Mountains, the Thompson Plateau, the Clear Range, the Okanagan Range, and the western side of the Okanagan and Shuswap highlands. Winters are cold and the summers are warm to hot. Vegetation in the valleys and basins is typically steppe or bunchgrass prairie that usually contains big sagebrush or occasional ponderosa pine or Douglas-fir. At higher altitudes, montane forests of Douglas-fir and lodgepole pine are extensive, while subalpine coniferous forests of subalpine fir, spruces and lodgepole pine occur at even higher elevations. Alpine areas are usually small and discontinuous. In British Columbia this ecodivision is represented by only one ecoprovince.
SOI - Southern Interior Ecoprovince
Location - the Southern Interior Ecoprovince lies east of the crest of the Coast and Cascade Mountains and west of the Columbia Mountains. In the north it abuts the Central Interior Ecoprovince, and it extends southward across the Canada-USA border to the northern edge of the dry Columbia Basin. It is the southernmost part of the Interior Plateau system. The leeward portion of the coastal mountains and the drier portion of the Columbia Highlands are included because they share much of the same climate as the main plateau.
The largest human population in the interior of British Columbia occurs in this Ecoprovince. Agriculture is largely based on grazing and forage crops, but orchards and vineyards are integrated with a large and successful tourist industry in the Okanagan Valley.
Climate - Because this Ecoprovince lies in the rain shadow of the Coast and Cascade mountains it contains some of the warmest and driest areas of the province in the summer. Air moving into the area has already lost most of its moisture on the west facing slopes of the Coast Mountains, reducing precipitation and contributing to clear skies, particularly in summer. The air moving across the plateau surface tends to be level, resulting in little precipitation, except through surface heating of lakes and streams.
In winter and early spring, there are frequent outbreaks of cold, dense Arctic air because there is no effective barrier in the north, once that Arctic air enters the interior plateaus of British Columbia. However, such events are less frequent, and of shorter duration, than on the plateaus further north. This cold air can get trapped in the large basins once the eastward flow of moist air resumes, causing the valleys to be much cloudier than the uplands. When the cold air fills a valley and is subsequently capped with warmer moister air, deep inversions and prolonged periods of cold weather at middle and low altitudes results. At the same time, milder weather will occur at higher altitudes and in areas away from the main valleys. There are occasional irruptions of hot, dry air from the Great Basin in the summer. They bring clear skies and very warm temperatures to the entire Ecoprovince.
Annual distribution of precipitation is similar to other plateaus in the interior of the Province. Surface heating in summer results in characteristic convective showers. The river valleys have high temperatures and strong convective currents and, with their local sources of moisture, contribute to showers on the surrounding hills. Skies over the valleys in summer are often free of clouds, even though there is extensive cloud cover over the uplands.
There are several north-south trending valleys, such as: the Fraser River, Okanagan Valley and Louis Creek faults that have created deep valleys and which play a role in allowing warm air from the Columbia Basin to the south to easily invade this ecoprovince, bringing dry conditions. Sagebrush-steep, bunchgrass-steppe and ponderosa pine forests benefit from such dry warm air.
Physiography - This Ecoprovince includes the Thompson Plateau, the Pavilion Ranges, the eastern portion of the Cascade Ranges, Okanagan Highland, and the western margin of the Shuswap Highland.
The whole area was glaciated during the Pleistocene and there are many surface features remaining, such as moraines, glacial lake deposits, and terraces. Most of the valley floors contain more recent floodplain deposits.
The Thompson Plateau is a gently rolling upland of low relief that is transitional with adjoining mountains. The rise of the plateau towards the mountains is gradual, with greater dissection of the surface as the slope increases. Lava beds obscure large areas of older rocks. The surface has been subdivided by the Thompson, Nicola and Similkameen rivers and the Okanagan River and Lake creating two large basins - the Thompson and Okanagan basins and two smaller ones, the Similkameen and Nicola basins. The Marble and Clear Ranges of the Pavilion Range form a high transitional zone between the Coast Mountains and the Interior Plateau; they have a steep front along the Fraser River to the west and a somewhat gentler slope into Hat Creek on the east.
The Okanagan and Hozameen ranges of the Cascade Mountains are composed of folded and metamorphosed sedimentary and volcanic rocks that have been intruded by granitic batholiths. The peaks and high ridges are serrated and show the effects of intense alpine glaciations. Cirque basins are particularly noticeable on north and northeast slopes. At lower elevations there are rounded ridges and dome-shaped mountains, which were overridden by ice. To the east, the mountains become lower and grade into the plateau surface. The ranges are deeply dissected by the Similkameen and Ashnola rivers.
The Okanagan Highland and the western portion of the Shuswap Highland lie in the eastern boundary of the Ecoprovince. These highlands form a gently sloping plateau that is transitional in height between the Thompson Plateau to the west and the Columbia Mountains to the east. This highland area has several rounded ridges separated by deep streams.
Vegetation - This ecoprovince supports a diverse set of upland and aquatic habitats that vary from open grasslands to dense coniferous forests and from small alkaline ponds to large, deep lakes. The vegetation communities are transitional with the most diverse grasslands occurring in the southern areas, with species such as antelope-brush, prickly phlox, threetip sagebrush, and many-spined prickly-pear cactus restricted to the southern-most grasslands. Many of these grasslands are now dominated by weedy invader species, such as spotted and diffuse knapweeds, summer cypress and Loesel’s tumble mustard. Forest communities reflect the moisture and elevational gradients from the high coastal mountains, across the interior plateaus, to the eastern Columbia Highlands. There is also a north-south gradient, with dry, hot climate tolerant forests in the south and cold, humid tolerant forests in the north. Much of the plateau upland is has been frequently burned, resulting in extensive lodgepole pine forests.
There are eight distinct vegetation zones. - Most of the valley bottoms are characterized by sagebrush-steppe and steppe (Bunchgrass Zone), the largest such occurrence in the province. Many of the glacial benches in the valleys are covered by big sagebrush. Grasslands of bluebunch wheatgrass with some big sagebrush occur at the lowest elevations in the four river basins. It has largely been reduced by excessive livestock grazing and is frequently replaced by extensive stands of big sagebrush dominated communities. The rate of succession in the big sagebrush/steppe communities is very slow because of severe summer drought. In the very dry valley bottoms of the southern Okanagan, antelope-brush and prickly-pear cactus dominate the lower sites. Grassland soils are dominant, having developed on sites varying from coarse gravel to silt. Those soils are often calcareous, with dark brown to black surface layers, and are rich in organic matter.
In most other valleys, the vegetation forms an open parkland zone with ponderosa pine (Ponderosa Pine Zone) and Douglas-fir intermixed with shrub-grassland communities (Interior Douglas-fir Zone). The common plants include saskatoon, big sagebrush, bluebunch wheatgrass, Idaho fescue, rough fescue, pinegrass, needlegrasses, and lupines. Floodplains have stands of black cottonwood, spruces, and trembling aspen, and a dense shrub growth of red-osier dogwood and black gooseberry. Horsetails are abundant at the edges. Soils vary from grassland soils to moderately weathered forest soils.
A lower montane vegetation zone occurs at slightly higher elevations (the Interior Douglas-fir Zone). The climax is normally the Douglas-fir forest that covers much of the Ecoprovince. The common plants include saskatoon, soopolallie, birch-leaved spirea, roses, pinegrass, twinflower, balsamroot, and kinnikinnick. Lower elevations within the zone support open, successional ponderosa pine and moderate elevation upland basins support meadow steppe habitats. The communities at higher elevations are typically closed lodgepole pine and pinegrass forests. Although forest regeneration is fairly fast, meadow steppe communities of Idaho fescue, bluebunch wheatgrass, and various forbs are persistent on southern exposures and rolling plains. The soils are generally weathered and calcareous.
The climax forest in the upper montane zone (Montane Spruce Zone) is a dense growth of white, Engelmann, or hybrid spruce. It is frequently mixed with subalpine fir. Transitional forests are dominated by lodgepole pine and Douglas-fir. The common understory plants include trapper’s tea, grouseberry, falsebox, pinegrass, arnicas, kinnikinnick, and lupines. Fireweed communities occur on disturbed areas. In addition the Interior Cedar - Hemlock zone occurs on the upper slopes or the east-facing slopes in the northeastern area of this Ecoprovince.
In the subalpine zone (The Engelmann Spruce - Subalpine Fir Zone), the climax is a dense forest of Engelmann spruce and subalpine fir but frequent fires have allowed the development of lodgepole pine forests. Many of those forests have now matured and have been damaged insects. Common understory plants include black huckleberry, white-flowered rhododendron, grouseberry, arnica, and Sitka valerian. Alpine larch and whitebark pine may occur near timberline. The open forests at higher elevations are intermixed with sedge-grass meadows. Soils change in the forested vegetation zones with increasing elevation and the associated cooler and moister climatic conditions. Soils at lower levels tend to be calcareous but with increasing elevation there is a gradient from weakly leached, moderately acid to increasingly leached and strongly acidic types. Forest litter accumulation also increases with elevation.
The Interior Mountain-Heather Alpine Zone is dominated by low sedge-grass communities and pockets of heath. Common plants include sedges, alpine timothy, trisetum, alpine fescue, mountain-avens, dwarf willows, and lupines. The soils are often a shallow layer over bedrock. They are strongly acidic, coarse in texture, and have turfy, dark-coloured surfaces underlain by reddish are brownish layers. Outcrops of bedrock are common.
Fauna - The Southern Interior Ecoprovince provides a vital link for forest-living wildlife species such as Lynx, Marten, Fisher and American Black Bear, from the boreal forests of central British Columbia, southward to the montane forests of Washington and Idaho. As well, it also provides a similar link for grassland species, such as Burrowing Owl, Long-billed Curlew, Gopher Snake and Western Rattlesnake, from the deserts and grasslands of the Great Basin and Columbia Plateau of Nevada, Oregon and Washington, northward to the grasslands of southern and central British Columbia. The grasslands of the Southern Okanogan Basin Ecosection have a fauna that is particularly interesting from a national perspective. Blotched Tiger Salamanders and Great Basin Spadefoot Toads breed in saline ponds, while Sage Thrashers and Brewer’s Sparrows sing from the fragrant sagebrush covered benches. Canada’s only population of Western Harvest Mice and Great Basin Pocket-mice are found in these grasslands habitats as well. The rocky cliffs along the valley walls provide habitat for Northern Scorpions, Western Rattlesnakes, Night Snakes, and Prairie Falcons.
The Southern Interior Ecoprovince marks the northern limits of ponderosa pine forests, and these forests also have a distinct fauna. White-headed Woodpecker and Gray Flycatchers are found nowhere else in Canada, while Flammulated Owls, Common Poorwills, Lewis Woodpeckers and Pygmy Nuthatches are commoner here than anywhere else in the country. The steep slopes and rocky cliffs provide habitats for Peregrine Falcon, white-throated Swifts, Canyon Wrens and California Bighorn Sheep.
The montane forests provide habitat for Mule Deer, White-Tailed Deer, Moose, Lynx and Bobcat, Cougar, Coyote and American Black Bear. Grizzly Bears, while never abundant in this ecoprovince they still occur in the Coast Mountains, Columbia Highlands and a few even remain on the northeastern portion of the Western Okanagan Upland. Mule Deer are the most abundant large ungulate in this Ecoprovince, although White-Tailed Deer have been extending their range westward from the Okanagan Basin and the Okanagan and Shuswap highlands. Bighorn Sheep, both native California Bighorn and the introduced Rocky Mountain Bighorn, occur on the rugged grasslands throughout the Thompson and Okanagan valleys and in the Clear Ranges.
Characteristic small mammals include spotted bats, pallid bats, Nuttall’s cottontails, white-tailed jackrabbits, Great Basin pocket mice, and western harvest mice.
This ecoprovince has the greatest diversity of birds in the interior of British Columbia and the most breeding species of all the ecoprovinces in the province; it holds 75% of all bird species known to occur and 70% of those species known to breed in the province. It is the centre of breeding abundance in the province for Swainson’s Hawk, California Quail, Mourning Dove, Burrowing Owl, Long-eared Owl, White-throated Swift, Lewis’ Woodpecker, Williamson’s Sapsucker, Pygmy Nuthatch, Western Kingbird, Yellow‑breasted Chat, and Lark Sparrow. Some species breed nowhere else in British Columbia; Ferruginous Hawk, Prairie Falcon, Gray Partridge (introduced), Chukar (introduced), California Gull, Flammulated Owl, Common Poorwill, Black-chinned Hummingbird, and White-headed Woodpecker; others breed nowhere else in Canada: Canyon Wren, Sage Thrasher, and Gray Flycatcher. It contains the only site in Canada that supports a major population of Tundra Swans during the winter.
The Racer and Western Rattlesnake are characteristic reptiles. Blotched Tiger Salamanders and Great Basin Spadefoot Toads are found nowhere else in the province.
Wetlands and riparian habitats are very rich in species such as, Painted Turtles, American Bittern, Long-eared Owls, and British Columbia’s only Yellow-breasted Chats. While on the South Thompson River hundreds of Tundra and Trumpeter swans, and Canada Geese spend the winter.
This ecoprovince supports both anadromous and freshwater fish. Anadromous species, include Pacific lamprey, steelhead, Chinook salmon, sockeye salmon, and white sturgeon. Freshwater fish include, rainbow trout (both native and widely transplanted populations), brook trout (introduced), bull trout, mountain whitefish, lake chub, redside shiner and northern squawfish.
The Southern Interior Ecoprovince is divided into four ecoregions containing 16 ecosections.
ITR - Interior Transition Ranges Ecoregion
This is a rugged, mountainous area that occurs on the leeward side of the Coast Mountains in the northwestern portion of the ecoprovince. It has both coast and interior transition climates. It is generally in a rain shadow, but moist coastal air enters the area via low passes to the west and south. In winter and early spring, cold Arctic air frequently erupts over this area from the Central Interior. Past glaciations were intensive, with the entire area being overridden by cordilleran ice-sheets, which blocked the southward flow of the Fraser River forcing the river to find another route south. The river escaped by way of the Thompson Plateau and ultimately southward through the Okanagan Lake Valley. This ecoregion has three ecosections.
- LPR - Leeward Pacific Ranges Ecosection
This is a very rugged mountainous area with deep, narrow valleys in the north, consisting bold mountains of the coastal granitic bedrock. The entire area was covered by Pleistocene glaciers that rounded the landscape and created many cirque-basins that still contain small glaciers and snowfields. This ecosection extends from Gold Bridge in the northwest, southeastward to the west slopes of the Fraser River above Boston Bar and North Bend. This ecosection is drained by: the lower Nahatlatch, Kwoiek, upper Stein, upper Joffre, Gates, Birkenhead, and upper Donelly streams. Lakes include: Birkenhead, Duffy, Nahatlatch and south half of Anderson lakes.
This area is generally under the influence of moist Pacific air, but drying interior systems in the summer and early fall provides for drying conditions. When large Arctic air masses build up in the interior of the province, this area is overridden by that dense cold air. Moist coastal forests dominate the valley bottoms, while drier interior-type forests occupy the mid to upper slopes. Rugged, barren alpine occur on the summits.
There are no permanent settlements in this ecosection. The Duffy Lake Road (No. 99) from Pemberton to Lillooet passes through the centre of this ecosection; a highway from Mount Currie to D’ Arcy on Anderson Lake follows the Birkenhead River, as does the British Columbia Railway; and the Hurley Pass road connects Pemberton with Lillooet via Gold Bridge. Logging with its attendant roads has occurred on most of the accessible lower slopes, and mineral exploration and mining has occurred throughout, especially in the Bridge River watershed. The central portion of the Stein Valley – Nlaka’pamux Heritage Park is the largest protected area, others include: Birkenhead Lake, Duffy Lake, Mehatl Creek and Nahatlatch parks.
- PAR - Pavilion Ranges Ecosection
This is a mountainous upland area that is transitional with the Coast Ranges to the west and the Interior Plateau surface to the east. In addition to the lower slopes of east side of the Coast Mountains it contains the Marble and Clear Ranges, Edge Hills and the northern extension of the Cascade Mountains. This area contains a large mass of limestone, as well as generally unlikely associated rocks of basalt, chert and serpentine. The Fraser River canyon, a strike-slip displacement fault, has moved over 140 km relative to each side of the river. This ecosection extends on the west side of the Fraser River, from south of Big Bar Creek past Lillooet to south of Lytton, and on the east side from west of Clinton south past Hat Creek to the west side of the Nicola River canyon, south of the Thompson River. The Fraser and Thompson rivers have dissected the upland surface and their deep, narrow valleys show evidence of a still rising upland surface. In addition to the Fraser and Thompson rivers this ecosection is drained by: the Kostering, Porcupine, Kelly, Pavilion, Hat, Twaal, Murray, Botanie, Nicoamen, Shakan and Nuaitch streams.
Generally, for most of the year, this area lies in the rainshadow of the Coast Mountains to the west. While hot subtropical area invades this area in the summer months, while cold Arctic air can invade from the north in the winter and early spring. Sagebrush-steppe and ponderosa pine forests dominate the Fraser and Thompson valleys, while Interior Douglas-fir and Montane Spruce forests occur on the upper slopes. Dry alpine vegetation occurs only as small pockets on the highest summits.
Settlements include Lillooet, Lytton and Pavilion. The Trans Canada Highway (No. 1) passes along the lower Fraser River and Thompson valleys from Boston Bar to Spences Bridge; the Lytton to Lillooet Highway (No. 12) passes along the east side of the Fraser River between those two settlements; and the Duffy Lake Road (No. 99) passes from Lillooet east past Pavilion Lake to Highway 97 north of Cache Creek. Logging has occurred throughout, as has livestock grazing; agriculture, mainly hay crops, has been developed on the level terraces above the Fraser River, and in the Kostering Creek and Hat Creek valleys. A number of protected areas have been established in this ecosection, Marble Range and Edge Hills are the two largest.
- SCR - Southern Chilcotin Ranges Ecosection
This is a foothills mountain area with high rounded mountains and deep narrow valleys. Even though most of this ecosection is in the Coast Mountains south of the Carpenter and Seton lakes and Gun Creek valley, it consists of the typical rugged coastal plutonic rocks of the Pacific Ranges, but on the north side, in the Chilcotin Ranges, it contains the more erodable, non-granitic rocks of sedimentary and volcanic origin of the Chilcotin Ranges. Sculpted cirque-basins are common on the southern portion and an extensive icefield persists in the headwaters of the Bridge River. The ecosection includes the Bridge River basin and extends southward across the lower Stein River valley to the mouth of Kwoiek Creek. This ecosection is drained to the east by the Bridge, Lockie, Hurley, lower Relay, lower Yalakom, Seton, Cayoosh, Texas and lower Stein and Kwoiek streams.
This area is under a rainshadow from the easterly moving coastal weather systems, but it is greatly affected by interior weather systems, especially in the winter, when dense Arctic air can invade into this area from the north. Interior Douglas-fir and Montane Spruce forests dominate the valleys and lower slopes while subalpine forests dominate the middle mountain slopes. Extensive alpine tundra, from the rugged glacier dominated areas in the west to rolling alpine meadows in the northeast occurs on the upper slopes.
Gold Bridge and Bralorne are the main settlements, and recreational cabins have been established around Gun Lake. The Hurley Pass Road passes through from Pemberton to Gold Bridge and Lillooet, and Duffy Lake Road (No. 99) passes through from Pemberton to Lillooet via Duffy Lake. Logging, mineral exploration and hard rock mining have been extensive throughout, Two large protected areas have been established here: the northern portion the Stein Valley - Nlaka'pamux Heritage Park is located in the southeast and the southern half of Spruce Lake Park occurs in the northwestern area of this ecosection.
NCR - Northern Cascade Ranges Ecoregion
This is a mountainous area that varies from rugged to rounded uplands that lies in the strong rain shadow created by the southern Coast Mountains and the northern Cascade Mountains. In British Columbia it is the northern extent of an ecoregion that extends along the east slope of the Cascade Mountains from the Methow Basin, west of the Columbia River in Washington, as far north as the upper slopes of the Fraser River canyon above Boston Bar. Most of the area is in a rain shadow, but moist Pacific air often dominates the western portion through low mountain passes, especially in the Coquihalla and Skagit valleys. Glaciations were light in the south, compared to more northerly environments while heavy glaciation was restricted to the higher mountain summits, with many lower slopes left unglaciated or lightly glaciated. This ecosection contains both wet coastal forests and dry interior types and is really transitional between the two types. This ecoregion is represented by two ecosections in British Columbia.
- HOR - Hozameen Range Ecosection
In British Columbia this is a rugged mountainous area lies mainly east of the Fraser River canyon as far north as Ainslie Creek and south to the slopes above Ross Lake; it extends southward just into Washington to Lightning and Castle creeks. The mountains increase in height and ruggedness from north to south and consist of metamorphosed sedimentary and volcanic rock with some granitic batholiths. The peaks are serrate and show the effects of intense alpine glaciation. This ecosection is drained to the east into the Nicola River by southern creeks in Prospect Creek watershed and upper Coldwater River; west into the Fraser River by Anderson and Upper Coquihalla rivers; southwest into the Skagit River by Nepopekum and Lightning Creeks; and southeast into the Similkameen River by Lawless, Tulameen and upper Similkameen streams.
The climate is transitional, although it is greatly affected by moist Pacific air entering this area via the Fraser, Coquihalla and upper Skagit valleys; although dry interior air can likewise enter west and southward from the Fraser, Nicola, and Similkameen valleys. Subalpine forests and rugged alpine dominate the higher slopes and dry montane forests dominate the lower elevations and moist Douglas-fir and western hemlock forests occur in most southwestern valleys.
The lodge, park and highway headquarters in E.C. Manning Park is the only settlement. The Trans Canada Highway (No. 1) passes along the northwestern margin from Boston Bar to just south of Lytton; the Coquihalla Highway (No. 5) passes over in the Coquihalla summit; while the Crowsnest Highway (No. 3) passes through E.C. Manning Park in the southern portion. Logging has occurred in the upland and valleys outside of E.C. Manning Park. There are four provincial parks of note here: E.C. Manning Park and the east half of Skagit Valley, Cascade and the Coquihalla Summit recreation areas. The small portion of this ecosection that lies in Washington is part of the Ross Lake Recreation Area and the Pasayten Wilderness Area.
- OKR - Okanagan Range Ecosection
This ecosection is characterized by high mountains in the south, with deep, dry valleys in the centre and south, lowering to rounded summits north of the Similkameen River. The higher summits show the affects of glaciations with serrate ridges and cirque-basin erosion. In British Columbia this mountain and basin area extends from Otter and Alison creeks and north of Osprey Lakes, south across the Similkameen valley to the international border. In Washington it continues southward, east of the Cascade divide to the south side of the Methow Basin. In British Columbia this ecosection is drained by the Tulameen, Similkameen, Alison, Otter, Hayes, upper Trout, Hedley, Ashnola, Ewart, Keremeos and Snohumption streams; while in Washington it is drained by, Pasayten, Methow, Lost, Chewack, Toats Coulee, Twisp and Gold streams.
This ecosection lies in a rainshadow of the higher Cascade Ranges to the west, although some moist can arrive via the lower Alison Pass. Summer temperatures are warm and hot dry sub-tropical air can arrive via the Columbia Basin to the southeast. Winters are cool, but cold dense Arctic air seldom occurs here unless under a large southward flowing air mass. Subalpine forests and rolling alpine tundra dominate the upper slopes, while sagebrush-steppe habitats occur in the wide, low elevation basins, at Princeton, lower Similkameen and Methow Basin, mainly on the eastern side of the ecosection.
Major population centres in BC include, Princeton, Tulameen, Hedley, Keremeos and Cawston; while in Washington, Twisp and Winthrop and the two major centres. In British Columbia the Crowsnest Highway passes through here in the south from E.C. Manning Park in the Similkameen Valley to Osoyoos; the Keremeos Kaleden Highway (No. 3A) connects the Similkameen and Okanagan valleys via Marron Valley; and the Yellowhead South Highway connects Princeton with Merritt. Outside the protected areas, this ecosystem has been extensively logged, roaded and grazed; agriculture has occurred in the valleys, with orchards being prominent in the Similkameen valley south of Keremeos. Protected areas in British Columbia include: Cathedral and the adjacent Snowy, Brent Mountain and South Okanagan Grasslands parks; the North Cascades National Park and the adjacent Pasayten and Lake Chelan-Sawtooth wilderness areas are the largest protected area in Washington.
OKH - Okanogan Highland Ecoregion
This is a transitional mountain and basin area lying between the Columbia Basin to the south, The Okanogan Valley to the west and the Columbia Mountains to the east. More than 95% of this Ecoregion lies within Washington - therefore the American spelling of Okanogan was used. This is a rugged highland and valley unit with dry forests in the uplands and sagebrush-steppe and bunchgrass-steppe in the valleys. Glaciation was light and restricted mainly to glacial lobes in the valleys, but erosion by the downwasting icesheets to the north give this ecoregion a more ancient appearance than the highlands to the immediate north.
This ecoregion contains two ecosections.
- SOB - Southern Okanogan Basin Ecosection
This is a wide trench located between the Okanagan Ranges to the west and the Southern Okanogan Highlands to the east. It is underlain by mainly metamorphic rocks. In BC it extends from south of Kaleden and just north of Okanagan Falls to the international border; while in Washington it extends from the international border to just south of Omaka. In British Columbia this ecosection is drained by the Okanagan River and Park Rill Creek; while in Washington it is drained by the Okanogan, lower Similkameen, lower Chopaka, Johnson, Bangparle, Tank, and Mission streams. Three large lakes occur here: the southern half of Skaha, Vaseaux and Osoyoos lakes.
This ecosection is a narrow valley that lies in the rainshadow of the Cascade Ranges and Southern Thompson Upland to the west as well surface heating in the summer creates convective currents that aid in keeping this area cloud-free and dry. Winters are typically cool, but cold dense Arctic air seldom invades here from the north. This ecosection has some of the hottest and driest climates in British Columbia, which is reflected in the extensive grassland communities, many of which have bitterbrush as a component. These grasslands, while often referred to as a ‘Pocket Desert’, are only a northern extension of the sagebrush -steppe from further south in the Columbia Basin, this area is too moist to be classified as a desert. Douglas-fir and ponderosa pine grow only on north-facing slopes and in draws where there is increased moisture.
In British Columbia, Okanagan Falls, Oliver and Osoyoos are the main communities; while in Washington, Oroville, Tonasket and Omak are the principal centres. The Okanagan – Vernon Highway (No. 97) extends from the international border north up the Okanagan Valley to Kaleden; the Crowsnest Highway (No. 3) passes along the southern portion in British Columbia connecting Keremeos with Osoyoos and Grand Forks; in Washington, Highway 97 extends from the international border south past Omak. Agriculture, especially orchards and grape growing are the main uses of the land and most of the valley bottoms are private land (Including Indian Reservations); there are many roads that service these farms. South Okanagan Grasslands, White Lake Grasslands and Vaseaux are the three largest protected areas in BC; there are no large protected areas in Washington.
- SOH - Southern Okanogan Highland Ecosection
This is transitional mountain area of low rounded mountains and narrow valleys. The bedrock here is a complete of granite, metamorphosed and sedimentary rocks, as well as some volcanic rocks. During past glaciation periods this area received smaller glaciers, but was greatly impacted by glacial melting to the north and as a consequence its slopes are highly eroded, giving this area a more ancient appearance than is common in more northerly environments in British Columbia. This ecosection barely enters into British Columbia it is restricted to a narrow area from Anarchist Summit east past the east flowing Kettle River, to the Grand Forks basin. In Washington this ecosection extends all the way from the international boundary south to the slopes above the Columbia River. In British Columbia this ecosection is drained by the lower Rock Creek, east-flowing Kettle, lower Boundary and lower Granby streams. While in Washington it is drained by the Kettle, Bonaparte, Myers, Sanpoil, Coyote, Omak and Columbia (now flooded by the Grand Coulee Dam) streams.
It is less affected by moist Pacific air coming directly from the west over the Cascade Range than moist air arriving from the southwest over the Columbia Basin. In the summer hot subtropical air can overwhelm this area and bring hot dry conditions. This ecosection is the least affected by cold Arctic air invasion from the north of any other ecosection in the Okanagan Valley. Dry ponderosa pine and Interior Douglas-fir forests dominate the valleys in British Columbia; although in Washington, grasslands dominate the large southern facing valleys and montane forest occupy the upland areas.
Major settlements in British Columbia include Bridesville, Rock Creek Midway, Greenwood, Grand Forks and Christina Lake; while in Washington only Republic and Curlew are major settlements. The Crowsnest Highway (No. 3) connects Osoyoos with Grand Forks and Christina Lake; in Washington highway number 20 connects Tonasket with Republic and Kettle Falls, and highway number 21 connects Grand Forks British Columbia with Republic and Grand Coulee in Washington. Logging, with its attendant roads and free ranging cattle has occurred throughout, while farming as been practised only in the lower valleys such as at Grand Forks. There are no large protected areas in either British Columbia or Washington in this ecosection.
TOP - Thompson - Okanagan Plateau Ecoregion
This is a broad forested rolling plateau with low elevation sagebrush-steppe dominated basins. The Ecoregion was heavily glaciated with much rearrangement of drainage of major rivers. The rivers and major lakes are all surrounded by cliffs and terraces of fine glacial-lacustrine materials. Glacial ice moved southward across the Thompson valley. Several large lakes occur in the valley basins, while hundreds of small lakes and ponds occur across the uplands. The plateau contains a great diversity of rocks, from granitic plutonic, to volcanic and sedimentary rocks, some of which lie buried under deep glacial drift. It has the driest and warmest climates in British Columbia, north of the Southern Okanogan Highland. The air is affected by moist Pacific air rising from the northwest or over the low mountain passes and cold Arctic air from the north often overrides the area, but only for short periods during the winter and early spring. Rain shadows and orographic drying occurs in the main basins and valleys. This ecoregion contains nine ecosections.
- GUU - Guichon Upland Ecosection
This is a plateau ecosection with steep sides and a rolling upland surface, it has a core of granitic and volcanic rocks that rise to over 1500 m at Fehr and Savona mounts, and to over 1600 m on Mounts Greenstone, Chuwhels, Mabel, Gypsum and Spaist. It is located in the uplands south and east of the Thompson River, northeast of the northern Cascade Mountains (Nicoamen Plateau) and west of Nicola and Stump lakes, upper Campbell and Peterson creeks, and Nicola Creek canyon cuts through the western side. This ecosection is drained to the north into the Thompson River by Durrand Creek; and into the Nicola River by the Droppingwater, Moore, Clapperton, Guichon, and Skuhun creeks.
This area is in a rainshadow of the higher Cascade Ranges and Coast Mountains to the west, although the higher elevations here receive more precipitation than do the lower slopes. Cold Arctic air reaches here unimpeded from further north when such systems overwhelm the Interior of the province. The lower slopes have both bunchgrass-steppe and ponderosa pine forests, while montane and subalpine forests dominate the mid and upper slopes. All the pine forests have been heavily impacted by the current mountain pine beetle outbreak.
Logan Lake is the only settlement, but extensive lodge and cottage development has occurred around many of the upland lakes. The South Yellowhead Highway (No. 5- the northern extension of the Coquihalla Highway) cuts across the upland and connects Merritt with Kamloops; the Merritt to Spences Bridge Highway (No. 8) passes through the Nicola Canyon; and the Highland Valley Road (No. 97 C) Connects Merritt to Ashcroft via Logan Lake. Logging with its attendant roads has been extensive in the upland; open pit mining for copper has occurred in the Highland Valley. Agriculture, mainly as hay crops has occurred in Meadow and Guichon creek valleys, and free ranging of livestock has occurred throughout. Tunkwa Park is the largest protected area.
- NIB - Nicola Basin Ecosection
This is an extensive basin, valley and upland area that lies between the adjacent Cascade Ranges, and the surrounding higher Thompson Plateau uplands. It is comprised of at least three separate volcanic units of tuff and lava. During periods of past glaciation a large ice-dammed lake filled the Nicola Valley forcing the Nicola River to drain north-eastward rather north-westward as it now does. In addition to the Nicola River, which divides this ecosection in two, this ecosection is drained by, the upper Campbell, Stumplake, Wasley, Quilchena and Coldwater streams.
This ecosection is in a rainshadow of the Cascade Ranges and Coast Mountains to the west, as well, surface heating in the summer creates convective currents that aid in keeping this area cloud-free and dry. Winters are typically cool, and cold dense Arctic air seldom invades here from the north. Because of its lower elevation (627 m at Nicola Lake) and rain shadow effects this area is dominated by sagebrush-steppe, bunchgrass-steppe and meadow-steppe communities, with dry ponderosa pine stands on the adjacent slopes. Douglas-fir grows as single stands in the moister draws and gullies and as dense stands on north-facing slopes and higher elevations. All the pine forests have been heavily impacted by the current mountain pine beetle outbreak.
Merritt is the largest community and smaller settlements include: Nicola and Shulos, although ranches, such as Douglas Lake and Quilchena boost considerable number of residences and both Stump and Nicola lakes have extensive recreational cottage developments. The South Yellowhead Highway (No. 5 Coquihalla Highway) cuts through the Nicola Valley from upper Coldwater River to Merritt to upper Clapperton Creek; the Merritt to Kamloops Highway (No. 5A) follows the Nicola and Stumplake streams north to Kamloops; in addition Highway (No. 8) connect Merritt to Spences Bridge as it passes through Nicola River Canyon. Hay farming and livestock grazing are the dominant agricultural enterprises, but golf course developments have occurred where feasible. Roche Lake Park on the northeastern upland is the only major protected area.
- NOB - Northern Okanagan Basin Ecosection
This is a wide trench and foothills area located between the Thompson Plateau to the west and the Northern Okanagan Highlands to the east. The valley is part of the major Okanagan Valley Fault that extends from Omak Washington north to Vernon, it has a large east-west bend between Peachland and Kelowna otherwise here it is generally a north-south trending fault. Much of this area was affected by valley glaciers that when they stagnated at the end of the ice age formed large lakes along it sides, those lake filled with glacial sediments, especially lacustrine silt, which now form the terraces above the Okanagan and Skaha lakes. The ecosection extends from middle of Skaha Lake in the south to the Deep Creek valley at Armstong in the north, it also includes the Coldstream Valley east to Lumby. Large lakes dominate the valley bottom especially Okanagan Lake, but also including: Skaha, Wood, Kalamalka and Swan lakes. This ecosection is drained by the northward flowing Deep Creek; as well as the streams that flow into Okanagan Lake and River, such as, Coldstream, the lower Mission, lower Trout, and Shingle creeks.
This ecosection is in a rainshadow of the Thompson Plateau and the Coast Mountains to the west, as well, surface heating in the summer creates convective currents that aid in keeping this area cloud-free and dry. In the summer hot subtropical air can overwhelm this area and bring hot dry conditions. Winters are typically cool, and cold dense Arctic air seldom invades here from the north. Because of its lower elevation (344 m at Kelowna) and rain shadow effects and valley corridor connection to the Columbia Basin to the south this area is dominated by sagebrush-steppe, bunchgrass-steppe and meadow-steppe communities, with dry ponderosa pine stands on the adjacent slopes. Douglas-fir grows as single stands in the moister draws and gullies and as dense stands on north-facing slopes and higher elevations.
The communities of Armstrong, Enderby, Vernon, Lumby, Cherryville, Okanagan Landing, Winfield, Kelowna, Westside, Peachland, Summerland, Naramata and Penticton have all seen a rapid increase in development and subdivisions since the mid-1960’s as this valley is the heaviest populated in the interior of the province. The Okanagan Vernon-Monte Creek Highway (No. 97) follows valley bottom from Osoyoos to Vernon; The Vernon-Sicamous Highway (No. 97A) continues north from Vernon to Enderby and Sicamous; the Vernon-Nelway Highway (No. 6) passes up the Coldstream Valley from Vernon to Cherryville. There are numerous paved roads that service the various communities and agricultural enterprises. The area has been extensively farmed for orchards, including vineyards. Kalamalka Lake Park is the largest protected area entirely within this ecosection, but there are parts of several large protected areas that are shared with adjacent ecosections, such as: Okanagan Mountain, Myra-Bellevue and Eneas Lakes parks.
- NOH - Northern Okanagan Highland Ecosection
This is a cool, moist, rolling upland, that is transitional in height from the lower plateaus to the west and the higher mountains to the east several river valleys dissect the upland surface. Much of the area is underlain by gneiss bedrock and differential weathering has produced gentle step-like slopes. In addition, glacial ice covered the greatly rounding the summits and upland and deposited a mantle of drift. This ecosection extends from the Kettle Valley in the south to Coldstream - Shuswap valley in the north and as well as the Okanagan Highland physiographic unit it includes a portion of the Thompson Plateau in the northwestern area. . This ecosection is drained by a number of streams including: the Craighton, upper Mission, Kettle, lower Granby, Boundary, Rock, upper Ellis, upper Vaseaux, Inkaneep and Kinney streams.
Vegetation zones reflect the higher relief than areas to the west and the moister climate caused by Pacific air rising over the Columbia Mountains to the east. The Douglas-fir zone occurs in the lower slopes of the main valleys. The Montane Spruce zone, with lodgepole pine dominated forests, occurs in the western and southern uplands; Engelmann Spruce - Subalpine Fir Zone occurs on the highest upland areas; and the moist Interior Cedar - Hemlock Zone occurs on valley slopes in the eastern portion of the ecosection.
There are few settlements here only Carmi and Beaverdell in the Kettle Valley. The Rock Creek-Kelowna Highway (No. 33) passes through the southwestern portion and the Vernon-Nelway Highway (No.6) passes by only at the summit in the upper Kettle River Valley. Logging with its attendant roads has been extensive in the upland surface and agriculture for hay crops has been developed only in the Coldwater and Kettle River valleys. Graystokes, Myra-Bellevue and the eastern half of Okanagan Mountain parks are the three largest protected areas in this ecosection.
- NTU - Northern Thompson Upland Ecosection
This is an area with rolling upland that is dissected by the North Thompson River and the Louis Creek Fault it rises in height (2633 m) in the Dunn Range, in the north. It extends across the northern portion of the ecoprovince, from lower Adams Lake and Mount Lolo in the south to Barriere, Little Fort and Clearwater and across the North Thompson River to the eastern plateau slopes. It includes the west central part of the Shuswap Highland physiographic unit and a small segment of the Thompson plateau. The valley sides are commonly steep due to glacial erosion and the total relief may be fairly great even though local relief in the uplands is moderate. In addition to the southward flowing North Thompson River this ecosection is drained by: the McGillivray, Lewis, Nisconlith, Sinmax, Barriere, Chu Chua and Joseph and streams. The southern Adams Lake and Dunn Lake are two of the largest lakes here, but there are many smaller lakes.
The climate is transitional between the drier and warmer climates further south and the moister and cooler climates to the north. It has warm, dry summers and wet, cool winters with relatively high snowfall. Vegetation zones reflect the complex climate: with rising moist air on the east; winter Arctic air outbreaks from both the northwest uplands and the east via the North Thompson valley; and the dry valley climates of summer.
Clearwater is the largest community, but other settlements include, Little Fort, Barriere, and Adams Lake. The South Yellowhead Highway (No. 5) cuts through the ecosection in the North Thompson valley from Clearwater to Barriere. Logging with its attendant roads has been extensive on the upland and slopes. Agriculture, primarily livestock and hay farming has occurred mainly in the North Thompson floodplain and in Lewis Creek. The western two-thirds of Dunn Peak Park occurs here and is the only significant protected area.
SHB – Shuswap Basin Ecosection
This is an area with rolling plateau uplands, steep sided plateau walls, and large inter-plateau lowlands. The Bolean Creek Fault, a southern extension of the Louis Creek Fault, divides the ecosection east to west. This is a major geological separation between the Intermontane Belt to the west and the Omineca Belt to the east. In the north this ecosection extends from Enderby and Salmon Arm northwest to Sorrento, Scotch Creek and Little Shuswap Lake; and in the south to Falkland, Westwold and Monte Lake. In addition to the Salmon River, this ecosection is drained by: the Little, Shuswap (from Enderby to Mara Lake), upper Deep, Chase and upper Monte streams.
It has a dry montane climate, except in areas where topographic shading provides an environment for the Interior Cedar- Hemlock forests. Vegetation zones generally reflect the wide low elevation basins and rolling upland surface. Sagebrush-steppe occupies the slopes, in the South Thompson and upper Salmon rivers basins, above that the Ponderosa Pine, Meadow-Steppe is dominated by Lodgepole pine forests, occurs over most of the uplands and only the higher areas have the colder, moister Engelmann Spruce - Subalpine Fir forests. Both pine species have been adversely affected by the recent mountain pine beetle outbreak.
Salmon Arm is the largest community, but there are many smaller communities and settlements such as: Enderby, Sorrento, Canoe, Grindrod, Falkland and Westwold. The Trans-Canada Highway (No. 1) cuts along the south side of the two Shuswap lakes, the Vernon-Monte Creek Highway (No. 97) passes up Monte Creek and down the upper Salmon River and the Armstrong-Salmon Arm Highway (No. 97B) passes up the northern extension of the Okanagan Valley. Logging with its attendant roads and free ranging cattle have been extensive in the upland and agriculture, including hay, livestock, dairy and fruit trees have been farmed in the Notch Hill to Salmon Arm to Enderby area as well hay and livestock farming has occurred in the upper Salmon valley and elsewhere. Enderby Cliffs Park is the only protected area of any size in this ecosection is located on the east-central boundary.
THB - Thompson Basin Ecosection
This area is a warm and exceptionally dry, broad low elevation basin, one of its characteristics is the cream-coloured silt cliffs, remnants of stagnated glacial ice and the ponding of silt-filled lakes during the waning of past ice ages. Elsewhere deep deposits of sand and gravel indicate were fast moving streams enter the glacial lakes and dropped their load of coarser materials. Volcanic rocks are common on the upland. The ecosection extends from the South Thompson River Chase in the east, the lower North Thompson River in the north and the west to the mouth of the Nicola River. The South Thompson River occupies the valley east of Kamloops, the North Thompson River occupies the valley north of Kamloops, and the Thompson River and Kamloops Lake occupies the valley west of Kamloops. Other streams include the lower segments of: Bonaparte, Deadman, Venables, Carbine, Durrand, Tranquille, Cherry, Peterson, Heffley, Knouff and Monte streams.
In the summer this basin has high temperatures and strong convective currents; skies over the valleys in summer are often free of clouds, even though there is extensive cloud cover over the adjacent uplands. There are occasional irruptions of hot, dry air from the Great Basin in the summer. In winter and early spring, there are frequent outbreaks of cold, dense Arctic air because there is no effective barrier in the north. That cold air can get trapped in the large basins once the eastward flow of moist air resumes, causing the valleys to be much cloudier than the uplands. When the cold air fills a valley and is subsequently capped with warmer moister air, deep inversions and prolonged periods of cold weather at middle and low altitudes results. The vegetation in this ecosection reflects the warm, dry climate with the Bunchgrass zone mainly consisting of sagebrush-steppe and bunchgrass-steppe occupying the valley and lower slopes, giving way to meadow-steppe and finally to Ponderosa Pine forest, at higher elevations, Douglas-fir occurs on the cooler aspects and narrow draws. The pine stands have been adversely affected by the recent mountain pine beetle outbreak.
Kamloops is the largest community, but others include, Chase, Lewis Creek, Pritchard, Savona, Cache Creek, Ashcroft and Spences Bridge. The Trans-Canada Highway (No. 1) cuts across the basin from Spences Bridge to Chase; the South Yellowhead Highway (No. 5) cuts southward from Lewis Creek through Kamloops to Lac Le Jeune; the Merritt-Kamloops Highway (No. 5A) is located from Kamloops past Knutsford to Merritt; and the Vernon-Monte creek and Cache Creek-Cariboo Highway (No. 97) enters the basin down Monte Creek, connects with the Trans Canada Highway as far as Cache Creek, the goes north up the Bonaparte River into the Cariboo, the Highland Valley Road (No. 97C) connects Logan Lake to Ashcroft and Cache Creek. Much of the basin has been settled or developed into livestock and hay production and inter-community roads are extensive. Lac Du Bois Grassland Park lies mainly in this ecosection; it is a large and significant grassland and is the largest protected area in the ecosection.
TRU - Tranquille Upland Ecosection
This is a rolling upland that has a plateau-front with steep sides on the south and east, but towards to north and west it grades onto the Cariboo Plateau and Cariboo Basin, it is the northern portion of the Thompson Plateau physiographic unit. It has thick basaltic lava beds that have been buried under extensive glacial debris, and which has been highly eroded along the south side above the Thompson River valley. Many lakes now fill the glacial depressions. This ecosection is drained by: the upper segments of: Deadman and Tranquille streams, as well as Criss, Watching, Jamieson, Whitewood and Peterson streams.
The climate is moist and cool, except during the summer months, which can be warm and dry. Pacific frontal systems reach this area via the open Chilcotin to the northwest or the Fraser canyon to the southwest. Cold Arctic air can irrupt across the Cariboo moving southward and imbed this ecosection with very cold conditions. Forests reflect the upland nature with Interior Douglas-fir, Montane Spruce and Engelmann Spruce – Subalpine Fir zones dominating. The extensive lodgepole pine forests have been severely impacted by the recent mountain pine beetle outbreak.
Vidette is the only named locality in this ecosection. There are no highways across this ecosection and only a small segment of the South Yellowhead Highway (No. 5) between Barriere and Little Fort follows the northeastern boundary. Logging with its attendant roads has been extensive across this upland area. And while not extensive, hay farming has occurred in the Tranquille Creek and Deadman River valleys; free ranging cattle have been allowed to graze much of the upland. Bonaparte Park is the largest protected area, but Arrowstone, Porcupine Meadows and the higher, forested portion of Lac Du Bois Grassland parks have also been established here.
WOU - Western Okanagan Upland
This is a rounded upland area that rises steeply above the Okanagan Basin to the east and more gently above the Nicola Basin to the west. It intergrades with the Okanagan Ranges to the south and the Monte Hills to the north. It is comprised of several plutonic units, the Okanagan Composite Batholith, that has been overlain by volcanic bedrock. In addition this ecosection has been sculpted and rounded by southeast flowing glaciers, which has caused deeply eroded streams on the eastern slopes. This ecosection is drained to the east into the Okanagan Basin by the upper potions of the Trepanier, Lambly, Shorts, Whitman, and Equesis streams; and into the Shuswap systems by the upper Salmon River, into the Nicola system by the upper Nicola, Quilchena and Pothole streams. Pennask Lake is the largest here, in addition many smaller lakes occur here as well.
This area is cool and moist, except during the summer when hot, dry air from the Columbia Basin to the south advects over this area. Moist Pacific air passes over and often shrouds this upland in cloud and brings rain in the summer and fall and snow in the winter. Cold Arctic can invade this area unimpeded from the north and can bring clear cold conditions for weeks on end. Forests are typical montane, upland forests for this ecoprovince and include Douglas-fir, Montane Spruce and Engelmann Spruce – Subalpine Fir, as well wetter forest of Interior Cedar – Hemlock occur on the northeast slopes, where topographic shading is most prevalent. Both lodgepole and ponderosa pine stands have been severely impacted by the recent outbreak of mountain pine beetle.
Other than summer cottages and lodges on many of the lakes there are no permanent settlements here. The eastern extension of the Coquihalla Highway, the Okanagan Connector (No. 97C) from Aspen Grove to Peachland, passes across the southern portion and the Osprey Lake Road from Princeton to Summerland passes by Osprey Lakes on the southern boundary. Logging with its attendant roads has been extensive on the upland, and free-ranging cattle occur throughout. Fintry Park is the largest protected area and smaller ones include: Pennask Creek, the western half of Eneas Lakes and northern two-thirds of Trepanier parks.