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Technical Thematic Report No. 11. - Western Interior Basin Ecozone+ Evidence for key findings summary

Ecozone+ Basics

Figure 1. Overview map of the Western Interior Basin Ecozone+.

Overview map

Long Description for Figure 1

This map of the WIBE shows the locations of cities/towns and bodies of water which are referred to within this report. This ecozone+ is located entirely in British Columbia, in the south central part of the province to the Washington, USA border. Cities in the northern part of the ecozone+ include, from west to east, Lillooet, Lytton, Merritt, Kamloops, and Salmon Arm. Cities in the south, from west to east, include Hope, Princeton, Keremeos, Osoyoos, Penticton, Kelowna and Grand Forks. Pemberton is shown but is outside the ecozone+. Rivers and lakes labeled with the ecozone+, from north to south, are the Fraser River, North Thompson River, South Thompson River, Kalamalka Lake, Okanagan Lake, Kettle River, Skaha Lake, Okanagan River, and the Similkameen River. Adams and Shuswap lakes are on the northeastern border of the ecozone+.

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The Western Interior Basin Ecozone+ (WIBE), shown in Figure 1 and summarized in Table 1, occupies the southern interior portion of British Columbia (BC) (see national map on page ii). The boundary of the WIBE is the same as the Southern Interior Ecoprovince of BC's Ecoregion Classification System. Footnote 6

The WIBE includes a wide range of ecosystem types, including forests, grasslands, wetlands, large and small lakes, major rivers and small streams, and some alpine and glaciated areas. It is unique in Canada for representing the northern extent of the Great Basin desert and has very high species richness and species rarity.

The ecozone+ has hot, dry summers, moderate winters, and, because it is largely in the rain shadow of the coastal mountains, relatively low precipitation.

Table 1. Western Interior Basin Ecozone+ overview.
Area57,071 km2 (0.6% of Canada)
ClimateDominated by the rain shadow effect of the coastal mountains, which limits
Hot, dry summers and moderate winters
River basinsThompson River draining to the Fraser River
Fraser River draining to the Pacific Ocean
Okanagan River draining to the Columbia River in Washington State
Similkameen River draining to the Okanogan River in Washington State
Kettle River draining to the Columbia River in Washington State
GeologySurficial materials primarily till (70%)
Contains the only significant concentration of black and brown chernozem
soils in BC footnote Footnote 7
SettlementKamloops is the largest settlement in the Thompson region
Lillooet is the largest settlement along the portion of the Fraser River within this ecozone+
Vernon, Kelowna, and Penticton are the largest settlements in the Okanagan
Princeton is the largest settlement in the Similkameen region
Grand Forks is the largest settlement in the Kettle region
From 1971 to 2006, the population of the ecozone+ more than doubled,
principally due to growth in the Thompson and Okanagan regions
EconomyServices, agriculture, and forestry are major employers
DevelopmentThe central Okanagan (Kelowna and surroundings) and south Okanagan (Penticton and surroundings) are experiencing high growth rates
National/global significanceThe WIBE includes many species at risk and is ecologically unique in Canada, because parts of the ecozone+ are the northward extension of the Great Basin sagebrush-dominated desert and its grasslands Footnote 8

Jurisdictions: The WIBE is contained entirely within BC. The traditional territories for the Northern Shuswap Treaty Society (Northern Secwepemc te Qelmucw Nation), St'at'imc Nation, Tsilhqot'in Nation, Lil'wat Nation/Mount Currie, N'Quat'Qua, Sto:lo Tribal Council, Peters, Stó:lo Xwexwilmexw Treaty Association, Westbank, and Yale overlap the WIBE boundaries. Esk'etemc, In-SHUCK-ch Nation, Ktunaxa Kinbasket Treaty Council, Laich-Kwil-Tach Council of Chiefs, Stoney Indian Band, Union Bar, Chehalis, Skwah, Douglas, and Xwémalhkwu Nation are adjacent to the WIBE.

Human population growth is increasing rapidly in the ecozone+ (Figure 2), particularly in the north, central, and south Okanagan (Figure 3). Parts of the landscape have been substantially altered for urban development and agricultural conversion. Forestry is also a major industry.

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Figure 2. Human population from 1971 to 2006 in the Western Interior Basin Ecozone+.
For these data, the WIBE was approximated by the Southern Montane Cordillera Ecoprovince of the National Ecological Classification System. There are minor discrepancies between these borders, but no cities occur in the non-overlapping areas.
Source: compiled from Statistics Canada, 2000 Footnote 9 and 2008 Footnote 10

Human population from 1971 to 2006

Long Description for Figure 2

This bar graph shows the following information:

Data for figure 2
Number of People (thousands) - 1971Number of People (thousands) - 1976Number of People (thousands) - 1981Number of People (thousands) - 1986Number of People (thousands) - 1991Number of People (thousands) - 1996Number of People (thousands) - 2001Number of People (thousands) - 2006

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Figure 3. British Columbia regional districts in the Western Interior Basin Ecozone+.
The Okanagan is comprised of the three districts in green.
Source: BC Ministry of Forests, Lands and Natural Resource Operations, 2007 Footnote 11

Human population from 1971 to 2006

Long Description for Figure 3

This map shows the regional districts within the WIBE. These include, from northwest to southeast, Squamish-Lillooet, Thompson-Nicola, North Okanagan, Central Okanagan, Okanagan-Similkameen, and the Kootenay Boundary.

Based on 2005 remote sensing data, forest is the predominant land cover in the WIBE (Figure 4). Approximately 14% is covered by grassland/shrubland habitats, which support high biodiversity and provide corridors for animal movement from the Columbia Basin to the south into the shrub-steppe and interior forests to the north.

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Figure 4. Distribution of major biomes in the Western Interior Basin Ecozone+ by remote sensing, 2005. Blue areas represent inland water bodies derived from the National Atlas of Canada; these were not included in the analyses. Source: Ahern et al., 2011 Footnote 12.

Distribution of major biomes

Long Description for Figure 4

This graphic presents a map and a stacked bar graph of the land cover of the WIBE, in 2005. The predominant land cover is forest (73%) located throughout the ecozone+. Shrubland is in the northwest (12%) as is snow and ice (2%) and low vegetation and barren (5%). Agricultural land (6%) and grassland (2%) run along low lying areas along the major rives in this ecozone+.

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West Kettle River
West Kettle River © R. Rae

Okanagan Lake shore
Okanagan Lake shore, near Summerland © R. Rae

Landscape on Okanagan Mountain
Landscape on Okanagan Mountain two years after the 2003 wildfire;
Okanagan Lake beyond © R. Rae

Mountain goats
Mountain goats, Cathedral Park © R. Rae

Ponderosa pine
Ponderosa pine, near Summerland © R. Rae

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Content Footnote

Footnote 6

BC Ministry of Environment. 2006. Ecoregion classification system [online]. British Columbia Ministry of Environment. (accessed 2 September, 2009).

Return to Footnote 6 référence

Footnote 7

Geological Survey of Canada. 1994. Surficial materials of Canada, map 1880A [online]. | Natural Resources Canada. (accessed 23 October, 2009).

Return to Footnote 7 référence

Footnote 8

Pitt, M. and Hooper, T.D. 1994. Threats to biodiversity of grasslands in British Columbia. In Biodiversity in British Columbia: our changing environment. Edited by Harding, L.E. and McCullum, E. Environment Canada. Delta, BC. Chapter 20. pp. 279-292.

Return to Footnote 8 référence

Footnote 9

Statistics Canada. 2000. Human activity and the environment 2000. Human Activity and the Environment, Catalogue No. 11-509-XPE. Statistics Canada. Ottawa, ON. 332 p.

Return to Footnote 9 référence

Footnote 10

Statistics Canada. 2008. Human activity and the environment: annual statistics 2007 and 2008. Human Activity and the Environment, Catalogue No. 16-201-X. Statistics Canada. Ottawa, ON. 159 p.

Return to Footnote 10 référence

Footnote 11

Forests, Lands and Natural Resource Operations. 2007. British Columbia regional districts [online]. Government of BC.
(accessed 11 July, 2013). Data to produce map downloaded from DataBC

Return to Footnote 11 référence

Footnote 12

Ahern, F., Frisk, J., Latifovic, R. and Pouliot, D. 2011. Monitoring ecosystems remotely: a selection of trends measured from satellite observations of Canada. Canadian Biodiversity: Ecosystem Status and Trends 2010, Technical Thematic Report No. 17. Canadian Councils of Resource Ministers. Ottawa, ON.

Return to Footnote 12 référence