Grasslands cover less than one percent of British Columbia, a province that is dominated by trees. Most of the grasslands in British Columbia are found east of the Coast and Cascade Mountains and south of Williams Lake.
The mountain ranges of British Columbia run in a generally north-south direction through the province with large valleys and plateaus between. Our fall and winter weather, bringing clouds full of rain and snow, comes from the Pacific Ocean to our west. As the clouds hit each of the mountain ranges they drop most of their moisture on the west side of the mountains, where abundant forests grow. The eastern side of the mountains receives much less rainfall and is therefore relatively dry. The diagram illustrates how much more rainfall Vancouver receives in a year compared to Kamloops.
In these dry, rainshadow areas, where there is little spring and summer rain, plant growth depends on the precipitation that falls during the winter. As spring and summer progress, any rain that falls evaporates before it can reach deep into the soil. Therefore most plants are not able to rely on that rain for growth. Grasses are adapted to thrive in these areas, where they start growing early in the season and finish their life cycle before the hottest and driest part of the year. Trees are unable to survive in these harsh conditions and are found only in areas of the grasslands where there is sufficient soil moisture.
Studies of pollen cores from lakes show that grasslands in BC have been much more extensive than they are at present. As the ice sheets that covered the province retreated at the end of the last Ice Age, grasses, sedges and shrubs were the first plants to become established on the barren landscape. A much warmer and drier climate that existed 7000 to 5000 years ago allowed grasslands to extend well into the Yukon Territory.
By 4500 to 3000 years ago forests had expanded and grasslands had retreated to approximately their present extent. Since then the province has experienced the coolest climate since the ice sheets retreated. The period between 1650 and 1850 was particularly cool and is often referred to as the Little Ice Age. Since 1850 there has been a general warming of the climate; that warming continues today.
The following are the major grasslands areas of the province:
The middle Fraser River and lower Chilcotin Rivers from Alexis Creek south to Lytton;
The Thompson River basin from Lytton east to Chase and north almost to Barriere;
The Nicola River valley and adjacent plateau areas around Merrit;
The Okanagan basin from Spallumcheen south to the US border;
The Similkameen valley from Princeton south to the US border;
The lower Kettle River valley around Grand Forks and Rock Creek;
The southern Rocky Mountain trench from Radium south to the US border;
The Peace River lowlands around Fort St. John and Dawson Creek; and
Southern Vancouver Island and the Gulf Islands.
Want to learn more about BC's grassland regions?
Go to Interactive Maps and choose a region.
The grasslands of British Columbia are not all alike, as differences in elevation, climate, soils, aspect and position in relation to mountain ranges have all influenced their development. The most extensive grasslands occur in the Southern Interior, south of the latitude of Williams Lake. They are the characteristic feature of the hot, dry middle Fraser River north of Lytton, the Thompson River valley at Kamloops, and the Okanagan valley. The grasslands of the Chilcotin plateau west of Williams Lake are less well known but are equally important as a landscape feature.
In the Peace River area around Fort St. John and Dawson Creek the wide open agricultural landscape was once a vast parkland of aspen, willow, and open grasslands. Grasslands there now only occur on the steep, south-facing slopes along the larger valleys of the Peace, Halfway, Beatton, Cameron, Morberley, Murry, Pine and Kiskatinaw rivers.
In all southern areas, bunchgrasses are the dominant grass and big sage the dominant shrub. In the far south of the Okanagan Valley where winters are milder, antelope-brush is the dominant shrub. In the Peace country, slender wheatgrass is the dominant grass with prairie sagewort repleacing big sage as the dominant shrub.
In the far north, dry grasslands occur on steep, south-facing slopes with shallow soils. In the sub-alpine and alpine areas of the province, open grasslands can be found on drier plateaus and slopes as well as in cold air drainage sites in the north such as the Muskwa-Kechika. Many of these upper elevation and alpine grasslands are known for their spectacular floral displays in summer.
The Garry oak meadow grasslands of southern Vancouver Island and the Gulf Islands are found in the rainshadow of the Vancouver Island and Olympic Mountains. They are generally restricted to rocky areas where soils are shallow.
One system of classification divides the grasslands of the southern interior into three distinct types based on differences in soils and elevation: Lower, Middle and Upper.
From valley bottoms to approximately 700 metres in elevation
Precipitation less than 250 millimetres annually
Widely spaced clumps of bluebunch wheatgrass, big sage, and a variety of early spring blooming plants characterize this grassland type. Adapted to drought conditions, many of these plants grow in early spring, taking advantage of snwo melt and available ground water. Also called shrub-steppe, these grasslands are found throughout the lower slopes of the Thompson, Okanagan and Fraser valleys. Antelope-brush is not able to withstand cold winters, so it is generally restricted to the most southerly parts of the south Okanagan and the Rocky Mountain Trench.
An important element of healthy open grasslands at lower elevations is the cryptogamic crust, a layer of lichens, mosses, liverworts and cyanobacteria that covers the ground between wildely-spaced bunchgrasses. The crust forms a protective cover for the soil, helps retain soil moisture, and prevents weedy species from becoming established. The cyanobacteria absorb nitrogen from the atmosphere and convert it to nitrates, a natural fertilizer for the soil.
From approximately 700 to 850 metres in elevation
Precipitation about 280 millimetres annually
A cooler, moister climate results fewer big sage and antelope brush, and more flowering plants in these grasslands. Although bluebunch wheatgrass is still the dominant grass, rough fescue becomes more abundant at higher elevations of the Thompson, Nicola and Okanagan valleys. There are more flowering plants in the middle grasslands than at lower elevations. These are the dominant grasslands of the Nicola Valley area.
850 to 1000 metres, depending on the region
Precipitation about 300 to 750 mm annually
Due to cooler temperatures and more precipitation in both summer and winter, upper grasslands are much more lush. While many shrub speciea are less frequent than at lower elevations, shrubs such as rabbitbrush often become more common. Rough fescue becomes the dominant plant in the Thompson and Okanagan regions along with Columbia needlegrass, Kentucky bluegrass, and Junegrass. In the Cariboo-Chilcotin plateau grasslands, bluebunch wheatgrass and needlegrasses dominate while fescues are absent. A wide array of flowering plants colour the grasslands from May to July.
Want to find out about water cycling in grasslands?
Go to Grasslands Ecosystems and click on Ecosystems Processes.
Want to find out more about grasslands communities?
Go to Grassland Communities and Habitats and choose a community.
Where in the world are grasslands?
Wayne Erickson (Grassland ecosystem)
Nicole Brand (Rainshadow Diagram)
Mike Duffy (Fraser River)
Paul Sanborn (Cryptogamic Crust)