Rare BC Ecosystems Under Siege

Time is running out for one of Canada's rarest and most biologically rich habitats. Over the past century and a half, some 99 per cent of British Columbia's Garry oak ecosystems have been cleared for logging, farming and urban development. Today, the last fragments are struggling to survive in the face of mounting pressure from developers, insect pests and invasive alien plants.

A mosaic of open rocky areas, grasslands, woodlands and meadows scattered with Douglas fir and lush wildflowers, Garry oak ecosystems range from southern BC to California. Restricted in Canada to the southeast coast of Vancouver Island, the southern Gulf Islands and a few isolated pockets in the Fraser Valley, they are listed by the provincial Ministry of Water, Land and Air Protection as endangered and at great risk of extirpation.

The rainshadow effect of Vancouver Island and the Olympic Mountains is responsible for the dry, Mediterranean-like climate of Garry oak ecosystems. As a result, many of the over 1000 different species of plants and animals found in these ecosystems are adapted to drought conditions–and a number are rare or endangered. Twenty-one species—such as the endangered Taylor's checkerspot butterfly and sharp-tailed snake—are listed as at risk nationally by the Committee on the Status of Endangered Wildlife in Canada. Another 93 are provincially at risk.

In addition to being threatened by the conversion of land for urban development and agriculture, Garry oak ecosystems have been affected by fire suppression and overgrazing by livestock, both of which have opened them to invasion by non-native plant species. In the past, fire likely played an important role in halting such invasion by scorching grass and shrubs and allowing trees to survive.

One particularly harmful introduced species, Scotch broom, has replaced native plants and changed soil nutrients, severely altering the make-up of these ecosystems. Garry oaks themselves are also under siege by insect pests such as gall wasps and phylloxeran aphids—both of which cause leaf scorching and premature defoliation, and weaken the trees by forcing them to expend energy trying to refoliate.

In an effort to prevent Canada's Garry Oak ecosystems from disappearing, a large number of government and environmental non-government organizations are working together to protect the few remaining relatively undisturbed examples of these ecosystems and to apply recovery strategies to other examples and their species at risk. In addition to being part of the recovery team, Environment Canada contributes funding to land acquisition and stewardship efforts through the Georgia Basin Ecosystem Initiative (GBEI)—a partnership that also includes Fisheries and Oceans Canada, and the BC ministries of Water, Land and Air Protection and Community, Aboriginal and Women's Services. The Habitat Stewardship Program administered through Environment Canada is also a source of on-the-ground funding for recovery and restoration efforts in these ecosystems.

The most recent purchases to receive GBEI funding were coastal bluffs on Galiano Island, which will be managed as a conservation area and bird sanctuary, land in Mill Hill Regional Park west of Victoria, and Canada's largest intact Garry-oak-dominated woodland on Saltspring Island. These parcels are key to the goal of establishing a network that is representative of Garry oak ecosystems across their geographic range, that supports native wildlife and plant life, and that is sustainable over the long term.

The importance of preserving this threatened habitat is underlined by emerging evidence that Garry oak ecosystems were at their most extensive during a warm, dry period after the last Ice Age. Their adaptation to summer drought could make these the ecosystems of the future, since such conditions may once again prevail as a result of global warming.

  Home |  Air |  Atmospheric Science |  Climate Change |  Environmemental Action |  Habitat |  Pollution |  Species at Risk |  Technology |  Water |  Weather |  Wildlife