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MS
H
ECOSYSTE
IN BRITIS
COLUMBIA
T RISKT RISK
AA
Grasslands
of the
Southern
Interior
Grasslands
cover less than
one percent of
British Columbia’s
land area.
Ministry of Sustainable Resource Management
Ministry of Water, Land and Air Protection
plants can go unnoticed, and reversing of cheatgrass may result in too fre-
such changes can be difficult. People quent, too intense fires in some
often recreate in grasslands, without valley-bottom grasslands.
realizing that the fragile, easily dis-
Why are grasslands of the turbed crust of lichens, mosses, and What are they?
southern interior at risk? algae (known as a microbiotic crust), rasslands of the southern interior are
n the hot, dry regions of the southern soils, and plants are easily damaged by semi-arid ecosystems dominated by
interior of British Columbia lie grass- both motorized vehicles and mountain bunchgrasses, shrubs, and non-grass
lands dominated by bunchgrasses, bikes.A single track can become an plants known as forbs. Grasslands
G
Iwildflowers, and dryland shrubs. erosion site, become weed infested, and occur in the hottest, driest valleys,
Grasslands were naturally limited in invite further traffic. Expansion of including the Okanagan, Thompson,
extent when European settlement began urban and suburban populations also Nicola, Fraser, Chilcotin, Kettle, and
in the mid-1800s, and significant areas brings more pets and recreation, which Kootenay, and represent the northern
of grasslands have been lost since that can in turn negatively affect grasslands extent of grasslands that once dominat-
time. Today, grasslands cover less than and the creatures reliant on them. ed what are now agricultural fields of the
one percent of British Columbia’s land Southern Interior grasslands have a Great Basin in the United States.
area and are one of Canada’s most long history of intensive livestock graz- These valleys lie in the rainshadow
endangered ecosystems. Scattered grass- ing,which reduced many low-elevation of the Coast, Cascade, or Columbia
lands also occur in coastal, central, and and gently sloping grasslands to little mountains, where winters are cool or
northern British Columbia; these grass- more than bare soil in the early 1900s. cold with relatively little snow.Valley
lands are also threatened but have differ- Many grasslands have partially or whol- heating and a flow of warm air from
ent ecological characteristics from Grasslands ly recovered through the Great Basin result in hot,dry sum-
those in the southern interior. carefully managed mers. In this semi-arid environment,
The warm climate and dra- are the most livestock grazing. long summer droughts can prevent
matic setting of grassland ecosys- valuable to However, unman- tree seedlings from establishing. Most
tems has long attracted human aged livestock graz- grasses, however, are well-adapted to
habitation, and today the loss of biodiversity, ing has degraded or capturing limited moisture.The shape
grasslands is evidenced by exten- the most prevented the recov- of bunchgrasses funnels moisture to
sive vineyards,orchards,hay fields, ery of other grass- a vast network of fine roots that are
human settlements, and commer- fragile to lands by exposing particularly effective at capturing mois-
cial and industrial developments disturbances. mineral soil, dam- ture near the soil surface. Bunchgrasses
in southern interior valleys.About aging bunchgrasses, survive drought by actively growing
one-third of the grasslands area in and promoting the only during spring and late autumn.
the Okanagan Basin and Boundary invasion of introduced plant species. Although bunchgrasses characterize
District has been lost to development; Historically, natural fires main- grasslands, some shrubs and a great
the North Okanagan has lost nearly tained grasslands on moister sites and diversity of forbs also occur. In spring,
half of its native grasslands. Ongoing at higher elevations by preventing trees moist soils bring the first flush of
population growth will add increasing from establishing. For about a century, blooms of easily overlooked sage-
pressures to remaining grasslands. Most fire has been largely excluded from brush buttercup and yellow bells,
of the losses and adverse effects are to grasslands through fire suppression, which are soon followed by the bright
valley-bottom ecosystems, which are cessation of burning by aboriginal pink and yellow splashes of bitterroot
the most valuable to biodiversity, the peoples, and removal of fine fuels and arrow-leaved balsamroot. The
most fragile to disturbances, and the through domestic grazing. Subsequent sequence of flowering continues until
slowest to recover. forest invasion has reduced some the hot, dry months of summer,
Many remaining grasslands have Cariboo-Chilcotin grasslands by more when the flashy colours of flowers are
been invaded by introduced plants than 30 percent since 1962. Although replaced by the subtle beauty of tawny
such as knapweed,sulphur cinquefoil, not well documented, significant areas tones and textures of dormant grasses
and cheatgrass. Since grassland species of many other grasslands have also and plants. Fall brings the wind-polli-
are subtly different and often poorly been lost. Ironically, as has happened nated flowers of big sagebrush and
known,changes from native to foreign in the United States, the introduction rabbit-brush shrubs. This diversity of
and site conditions, including aspect mo
and slope. In general, moisture, forb val
diversity, productivity, and plant and Co
litter cover increase with elevation, gre
while microbiotic crust cover and diver- pe
sity decrease. ext
Valley-bottoms are the hottest and clim
driest areas, and are commonly domi-
nated by dryland shrubs with widely ing
spaced bunchgrasses such as blue- sta
bunch wheatgrass and needle-and- tio
thread grass, scattered forbs such as are
prickly pear cactus, and a diverse 10
microbiotic crust. These grasslands are ha
the most sensitive to disturbance, and fir
have been the most affected to date by fue
livestock, invasive plants, and develop- en
ment.Middle slopes of valleys are usu- lin
ally dominated by bunchgrasses with a the
wider diversity of forbs; scattered areas in
of shrub-steppe also occur. an
At the upper edges of valleys and thi
on adjacent plateaus, slightly cooler tim
and moister climates result in condi- D
tions favourable for both forests and ex
grasslands. Here, frequent low-inten- to
sity fires likely played a key role in lan
maintaining grasslands in a mosaic ele
with open forests. With fire exclusion, mo
many of these grassland areas have
plant species is paralleled by a diver- Southern interior grasslands include been invaded by trees and are shrink- tle
sity of mammals, birds, amphibians, ecosystems dominated by bunchgrasses, ing rapidly. When undisturbed, these ye
reptiles, and insects that are adapted and ecosystems dominated by dryland grasslands are dominated by rough or lan
to and depend on grassland eco- A careful shrubs such as sage- Idaho fescue in southern valleys, and ste
systems for food, shelter, and brush or antelope- by porcupine grass in the Cariboo- of
breeding sites. look reveals brush with grasses Chilcotin. They have a wide diversity th
Underneath the more obvious a tiny and forbs. These of forbs, although their microbiotic tio
plants of undisturbed grasslands shrub-dominated crusts are often less diverse and less int
lies a fragile, easily disturbed crust of world of ecosystems are some- continuous because thicker litter lay-
lichens, mosses, and algae known lichens and times referred to as ers limit their development. W
as a microbiotic crust. A careful shrub-steppe. Both co
hands-and-knees look reveals a miniature livestock grazing and What is their history?
tiny world of lichens and minia- mosses. fire exclusion have n British Columbia, southern interior
ture mosses, many of which reveal likely resulted in the grasslands are ancient communities
their brightest colours only after a rain- conversion of some bunchgrass- that probably became established from G
fall. This crust binds the soil together in dominated areas to shrub-steppe. Ithe south about 10 000 years ago as the geo
an irregular surface that enables soils to Grasslands exhibit distinct ecologi- Pleistocene glaciers were melting. Dur- ern
better capture moisture, prevents wind cal trends associated with moisture ing a warm climatic period from about sm
and water erosion, and provides some and temperature gradients, which 9000 to 4700 years ago, species from the are
nitrogen to grassland plants. are in turn related to elevation changes arid Great Basin west of the Rockies hig
moved northward into the hot, dry Why are they important?
valley bottoms of southern British Range of southern interior grasslands. rasslands have a wide range of
Columbia.Grasslands covered a much important values, one of which is
greater area during this warm climatic their intrinsic value – they are an
period, but shrunk to their current Gessential part of British Columbia’s
extent about 4000 years ago when the and North America’s unique biodiver-
climate became moister and cooler. sity and natural heritage. Grasslands
Fire was historically a strong shap- are naturally rare and have been sub-
ing influence in grasslands. Fires, stantially reduced by human activities.
started both by lightning and tradi- All of us are reliant on the ecosystem
tional burning by aboriginal peoples, services that grasslands provide,
are estimated to have occurred every including the safe capture, storage, fil-
10 to 20 years. Most grassland plants tration, and release of water and clean
have structures that are able to survive of grasslands are privately owned, 10 air. Grasslands provide places for recre-
fires moving through the fine grass percent are within Indian Reserves, ation, education, eco-tourism, ranch-
fuels and thrive on the flush of nutri- and less than half are on Crown land. ing, and hunting. Healthy grasslands
ents released by burning. Tree seed- Of publicly owned grasslands, about with dense grass are more resistant to
lings were able to establish only where 90 percent are under grazing tenures. invasion of non-native plants and pro-
there was more moisture or Fire was Just over three-quarters vide more forage and wildlife habitat
in an unusually moist year, of private land grass- than degraded grasslands. Grasslands
and most did not acquire historically lands lie within the Agri- are important to aboriginal peoples,for
thick, fire-resistant bark in a strong cultural Land Reserve. harvest of bitterroot, balsamroot, and
time to survive the next fire. Only a small percent- other plants found in grasslands.Grass-
During the past 140 years,fire shaping age of our grasslands are lands provide a scenic backdrop for
exclusion has allowed trees influence in protected – Eight per- many communities and are places to
to invade and shrink grass- cent lie within Crown enjoy nature and observe wildlife.
lands, especially at higher grasslands. protected areas, and The warm climate and aesthetic values
elevations and on cooler, non-government con- of grasslands have contributed to
moister sites. servation organizations have pur- increased real estate values in many
Grasslands have been grazed by cat- chased less than one percent of pri- valleys – ironically this has increased
tle, horses, and sheep for the last 140 vately held grasslands for protection. the threats to the beauty and bio-
years. Human populations in grass- Larger grassland protected areas diversity that has attracted people to
land-dominated valleys have increased include Lac du Bois Grasslands Pro- live there.
steadily since the mid 1800s. Both tected Area near Kamloops, South Many of the values of grassland
of these factors have played a role in Okanagan Grasslands Protected Area landscapes lie in the diversity of eco-
the present condition and distribu- west of Oliver and Osoyoos,and Churn systems that occur there, including
tion of British Columbia’s southern Creek Protected Area west of the woodlands, old forests, wetlands,
interior grasslands. Fraser River from Clinton. riparian areas, aspen copses, cliffs,
Nearly all grassland and shrub- rock and talus. Most of these ecosys-
What is their steppe natural plant communities are tems are also considered threatened
conservation status? considered at risk. Presently, 15 of or endangered, and together this
rasslands in the southern interior these plant communities have been diverse mosaic of ecosystems within
occupy less than one percent blue-listed (special concern) or red- the grassland environment provides
(662 872 ha) of British Columbia’s listed (endangered); evaluations for habitat for a wide diversity of plants,
Gland area. Because grasslands are other grassland plant communities mammals, birds, reptiles, amphib-
geographically restricted to hot south- are pending. Many other plant com- ians, and invertebrates.
ern interior valleys and occupy a very munities associated with grassland Although grasslands cover a very
small portion of British Columbia’s land landscapes, such as wetlands, aspen small portion of British Columbia’s
area, these ecosystems are considered copses, and woodlands, are also land area, they provide habitat for
highly endangered.More than 40 percent endangered. more than one-third of the province’s
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