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Georgia Depression

georgia

Grassland Region

Area, ha

Ecoprovince

Georgia Depression

24,000

Georgia Depression

Ecosections

Area, ha

Nanaimo Lowland

Southern Gulf Island

12,000

12,000













Grassland Landscapes

georgia1Grasslands on the coast are represented by scattered patches, no bigger than two hectares, of Garry oak savannah and Garry oak parklands. These communities are found along the North American west coast and are most extensive in Washington State. They are at their northern extent in the Gulf of Georgia, providing a contrast to the dark forests of coastal British Columbia

The mountains of Vancouver Island create a rainshadow effect in the Gulf of Georgia where mild winters and warm, dry summers, along with summer winds from the southwest, provide ideal growing conditions for species found further south.







georgia2Unique features

The rocky coast of southern Vancouver Island and the Gulf Islands provide some protection from development and grazing for Garry oak communities. Thin soils and very warm conditions on often near-vertical cliffs create special habitats for some unusual combinations of plant species and some very early blooming dates.
In Thetis Lake Park on southern Vancouver Island, red-flowered currant, shooting star and early saxifrage can be found blooming from mid-February to mid-March. Chocolate lily, two species of camas and calypso orchids bloom in April. Monkey flower may be found at the base of cliffs where moisture gathers.

Plant Communities

Ecosections

BEC Zones with grasslands1

Major2 grassland BEC Subzones and Variants

Nanaimo Lowland

Coastal Douglas-Fir Zone

CDFmm: Moist Maritime Coastal Douglas-fir Subzone

Southern Gulf Island

Coastal Douglas-Fir Zone

CDFmm: Moist Maritime Coastal Douglas-fir Subzone

1. Click here to find out more about the Biogeoclimatic Ecosystems Classification(BEC) System

2. Over 3,000 hectares

CDFmm: Moist Maritime Coastal Douglas-fir Subzone: 2,400 hectares

Found on rocky cliffs and gentle, south-facing hillsides on the east coast of Vancouver Island from Comox to East Sooke and through the Gulf Islands, the largest grassland area is on the south-facing slopes of Saturna Island. The shallow soils on which the Garry oak communities grow have developed on glacial deposits left behind after the Pleistocene glaciation.

georgia3Garry oak and arbutus are the dominant trees, with a rich carpet of spring flowering plants. The composition of the communities varies between sites. Garry oak is dominant in most communities on southern Vancouver Island, but where rock outcrops reduce soil depth, arbutus is the dominant tree species. A mosaic of communities throughout the range of Garry oak ecosystems include coniferous forests, parklands, shrub-steppe, rock outcrops flower meadows and small grasslands.
Some species from interior grasslands are also found in Garry oak communities, including brittle prickly-pear cactus, chocolate lily, death camas, mock-orange, northern wormwood and tall Oregon grape. Common snowberry and Nootka rose are found on moist sites.

Garry oak communities cover only 5% of their original range with less than 1,000 hectares in a pristine state. The communities have become fragmented by a century of development, by livestock grazing and by the spread of introduced plants. Scotch broom, Kentucky bluegrass, orchard grass and sweet vernalgrass are only a few of the non-native species that continue to threaten Garry oak savannah and parkland ecosystems.

Key Plant Species

Garry Oak

  • Heavy-looking tree with deeply ridged grey bark up to 25 metres tall
  • in rocky areas or shallow soils may be quite stunted
  • leaves are dark green and oak-shaped, usually single and alternating on the branch
  • flowers are tiny, coming out with the leaves
  • males flowers a hanging catkin, female flowers single
  • acorns are 2-3 cm long, edible, but with tannins
  • Salish peoples ate acorns after soaking to remove the tannins
  • oak bark was used in medicines


Wildlife

The fragmented Garry oak communities are used by a large number of wildlife species for at least some of their habitat requirements. At least 169 species use these communities at some time of the year, including 140 invertebrates, 12 reptiles and amphibians, 90 birds and 28 mammals. Many of the insects are restricted to particular communities and a specific plant species within the community. Snakes, such as the garter snakes, and Northern alligator lizard prefer the warm, dry communities while the many wetlands are home to rough-skinned newt and red-legged frog.

Resident and migratory birds use Garry oak habitats for parts of their needs, including Cooper’s hawk, Western screech-owl, brown creeper and yellow warbler. Some species, such as vesper sparrow, Western meadowlark and Western bluebird, typical southern interior grasslands birds, rely on these communities for all their needs. As communities shrink in size or disappear these species become increasingly threatened.

Large mammals such as black-tailed deer, black bear and Roosevelt elk are found in Garry oak communities for more than periodic use or travel corridors. Small mammals are more numerous ten species of bats have been recorded.

Many introduced species use Garry oak communities, often successfully competing with native species. The gray squirrel, Eastern cottontail, European starling and house sparrow are only four such species. The starling and house sparrow compete directly with native species for food and nest sites.

Small areas of Garry oak communities in the Georgia Depression region are protected in parks and other conservation areas where access is managed to reduce the impact on plant communities. Research projects are giving managers a better understanding of the native species and their particular needs.

Check the list of wildlife viewing sites publications.



Species at Risk

Red- and Blue-listed grassland elements in the Georgia Depression

Element

Red List*

Blue List**

Vascular Plants

Plant Communities

Insects

Reptiles and Amphibians

Birds

Mammals

Total Elements

30

2

10

1

7

0

50

17

0

5

0

5

3

30

*Red list: List of ecological communities, and indigenous species and subspecies that are extirpated, endangered or threatened in British Columbia.

**Blue list: List of ecological communities, and indigenous species and subspecies of special concern (formerly vulnerable) in British Columbia

47 listed plant species are found in the Georgia Depression region, many of which are at the northern limit of their range. Garry oak is the only oak species in BC, while plants associated with it such as great camas and common camas, Lemmon’s needlegrass, deltoid balsamroot and Macoun’s meadowfoam are all at the northern limit of their range. Coast microsis, California buttercup and Howell’s montia are only some plants that listed in BC but abundant further south.

Most animals found in Garry oak communities only use the community for part of their annual needs as the areas are so small. Some insects are known to feed specifically on one particular species of plants while reptiles and amphibians, with a smaller range, may rely heavily on these communities. The red-tailed snake is one such species with a habitat restricted to dry, south-facing slopes. Townsend’s big-eared bat is blue-listed and only one of ten other listed bats that use these habitats for foraging, roosting and breeding.

A Species at Risk Profile: Deltoid balsamroot

Red-listed in BC Listed under the Federal Species at Risk Act (SARA)

Deltoid balsamroot (Balsamorhiza deltoidea) is a common species at the northern limit of its distribution in BC. Related to the balsamroots of the southern interior and Chilcotin grasslands, it is the only balsamroot west of the Cascade Mountains.

Large, showy yellow sunflower heads shine above the long lance-shaped leaves in early spring. Fine white hairs on the leaves and stems of the plant act like a white t-shirt, reflecting the sun and helping to cool the plant. A deep tap root allows it to thrive in the dry, rocky situations of Garry oak communities on southeastern Vancouver Island.

For more information on species at risk in BC, visit our SAR page.

For definitions of technical terms, please see the GLOSSARY.

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