Preserving Canada’s Garry Oak ecosystem

Vegetation sampling in a Garry Oak meadow

The Garry Oak (Quercus garryana) ecosystem is one of British Columbia’s most unique and diverse, but also threatened, habitats. Though covering less than 0.1% of British Columbia’s land area, Garry Oak sites, ranging from shady woodlands to open meadows to rocky outcrops, are disproportionately rich in biodiversity. Under the oak trees, more plant species than in any other terrestrial ecosystem in coastal British Columbia can be found and many of these are endemic species.

In recent history, Garry Oak sites have been altered by urbanisation, forestry and agriculture to the extent that less than 5% remain in a near-natural state. Exotic plant species, overgrazing by domestic livestock and lack of fires also threaten the ecosystem’s integrity. This combination of limited distribution, species richness and significant threats makes Garry Oak habitats some of the most endangered in British Columbia. The result is that more than 100 species of plants, mammals, reptiles, birds, butterflies and other invertebrates are classified as threatened or endangered.

A Rocha Canada has been working on the conservation of the Garry Oak ecosystem and the stewardship of key sites since 1999. Initial work, supported by the Habitat Conservation Trust Fund, included species surveys and management recommendations at Pioneer Pacific Camp on Thetis Island. In 2004, A Rocha Canada, in partnership with Trinity Western University (Langley, British Columbia), started the study and management of the Crow’s Nest Ecological Research Area, a 29.4 ha Garry Oak site on Salt Spring Island. Working with A Rocha staff, Trinity Western students have been making an inventory of species, setting up monitoring programmes and initiating research. A total of 209 plants (174 vascular, 35 non-vascular), 54 birds, 3 reptiles and numerous other species have been identified on the site.

Common Camas

One study is looking at the effects of grazing by domestic sheep on Garry Oak sapling growth by using wire mesh to exclude sheep. Preliminary results show that Garry Oak seedlings were not significantly affected by grazing over three years, but because this is a long-term study the monitoring of the impact continues. Another study initiated in 2005 is examining the mechanisms of competition by an introduced grass species, Sweet Vernal Grass Anthoxanthum odoratum, against native species. A third major study is looking at the impact of encroachment on the Garry Oak habitats by the native Douglas Fir (Pseudotsuga menziesii) and is investigating the possibilities for restoration by controlling the firs. This research will not only inform a management plan that is currently being written to guide stewardship of the Crow’s Nest area, but will also have an impact on Garry Oak habitat management throughout its range.

Project leader: Patrick Lilley. For further infomation contact canada@arocha.org

Partners: Trinity Western University, Pioneer Pacific