Garry Oak Ecosystems Recovery Team (GOERT)

What Remains of Garry Oak Ecosystems?

Collectively, Garry oak and associated ecosystems are among the most endangered in Canada. Once common in coastal areas of southwest British Columbia, less than 5% of these ecosystems remain in near-natural condition. Most of the remnants are in isolated, fragmented communities that have no connection to other Garry oak communities, thereby reducing migration of populations or mixing of genetic material of species from one area to another.

At this time, because so much habitat has been lost or degraded, more than 100 species of plants, mammals, reptiles, birds, butterflies and other insects are officially listed as “at risk” in these ecosystems. 

A deep soil Garry oak ecosystem at Cowichan Garry Oak Preserve (photo by Shyanne Smith)

Originally, two major types of ecosystems occurred in the Garry oak areas: 

• Deep soil sites — Known as parkland Garry oak communities, these are a mosaic of shrubs, trees, and meadows of flowers and grasses are typical of deep soil sites. Almost all of the deep soil parkland sites in the Victoria region were cleared for agriculture and urban development. Many large Garry oak trees remain, but most have lawns, roads, agricultural fields, golf courses or blacktop beneath them, rather than native plant communities. On Vancouver Island, only 1.5 % of the original deep soil sites remain.
• Scrub oak shallow soil sites — More of the scrub oak shallow soil sites exist, as many of these rocky areas are difficult to develop. Spring flowers, grasses and mosses originally dominated the understorey of these rock outcrop communities. Many of these native plant communities have been invaded by weedy species such as Scotch broom, daphne, and agronomic grasses. On Vancouver Island, only 44% of the shallow soil sites remain.

Historic & Current: Greater Victoria & Saanich Peninsula

The following map and the table compare the 1800 and 1997 distribution of Garry oak ecosystems in the Victoria area. The Municipality of Highlands was not included due to lack of data.

The areas covered are where Garry oak (Quercus garryana) was believed to be the dominant tree cover, or co-dominant cover with Douglas-fir (Pseudotsuga menziesii) or arbutus (Arbutus menziesii). Other areas may have had and still have Garry oak as a minor component of the ecosystem; however, these areas were not considered for this mapping project.

Download the map: Historical Victoria & Saanich Peninsula Map (2002)

Historic & Current: other regions

The following maps and tables compare the distribution of Garry oak ecosystems in regions other than Greater Victoria and Saanich Peninsula areas in 1800 and 2003.

The colour gradations on the map indicate the percentage of each patch that is covered by Garry oak ecosystems (Garry oak woodlands, Garry oak meadows, etc.). For example, the areas with the lightest green or red colour patches contain less than 10% Garry oak ecosystems, and 90% is comprised of other habitats, such as conifer forests or wetlands. The darkest shades represent areas that are totally covered by Garry oak ecosystems (100%).

Cowichan Valley & Saltspring Island

Download the map: Historical Cowichan Valley & Saltspring Map (2004)

Note that only 4.5% of the deep soil sites have not been developed, and the remaining “scrub oak” sites are on rocky outcrops, steep slopes and similar shallow soil areas that are less appealing for agriculture and residential uses.

Nanaimo, Parksville & Nanoose Area

Download the map: Historical Nanaimo, Parksville & Nanoose Area Map (2004)

In the Nanaimo, Parksville and Nanoose area, only about 33% of the Garry oak habitats from1800 exist today. Most of these fragments are tiny, isolated, and overrun with non-native species such as Scotch broom, Himalayan blackberry and non-native grasses. Although there have been severe losses of Garry oak habitat in the Nanaimo and Parksville area, there is an opportunity to protect several outstanding sites. Harewood Plains and Harmac/Joan Point are relatively intact remnants of shallow soil Garry oak ecosystems, containing several rare plants of provincial and national significance. For example, Muhlenberg’s centaury (Centaurium muehlenbergii) has been found in Canada only at Harmac and at one park in Victoria. All of Canada’s seven remaining populations of bog bird’s-foot trefoil (Lotus pinnatus) are clinging to survival in the Nanaimo area. Experts currently rank Harewood Plains as the highest priority Garry oak ecosystem site on Vancouver Island for conservation.

A few examples of deep soil Garry oak ecosystems persist in the Enos Lake and Brennan Lake areas.

Comox Valley, with Denman & Hornby Islands

Download the map: Historical Comox Valley with Denman & Hornby Islands Map (2007)

No measurable shallow soil ecosystem occurred in the Comox valley. The 98 ha shown in the table (above) occurred on Hornby Island, with over half still remaining (57 ha).

Credits

• Lea, T. 2006. Historical Garry Oak Ecosystems of Vancouver Island, British Columbia, pre-European Contact to the Present. Davidsonia 17(2):34–50
• Ecosystem mapping by Ted Lea and Kate Miller, Terrestrial Information Branch, British Columbia Ministry of Sustainable Resource Management, Victoria, BC
• Digital Products by Dan Horth and Duncan Richards of HR GISolutions
• Funding was provided by the BC Ministry of Sustainable Resource Management, Ministry of Water, Land and Air Protection, BC Ministry of Environment, Parks Canada, and Forest Renewal British Columbia