Why are the ecosystems at risk?
Garry oak ecosystems are restricted primarily to the southeast coast of Vancouver Island and the southern Gulf Islands. These ecosystems occupy only a small portion of the Coastal Douglas-fir zone, which itself comprises only 0.3 percent of the land area of the Province.
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During the last 150 years, agricultural and urban development has consumed substantial areas of the natural landscape. Overall, urban development has had a major impact. The largest continuous occurrence of Garry oak woodlands was formerly in the urban center of Greater Victoria, a region that is now almost completely developed. Parkland and meadows, once common in this area, are in extreme peril. Fire suppression has allowed Douglas-fir to invade areas once dominated by Garry oak.
The trend continues, with many developments imminent. Today, Duncan, Nanaimo, Hornby Island, Saltspring Island, and Comox all have Garry oak landscapes threatened by development. Although the death may be a slow one, construction near oaks can lead to tree mortality. |
The Matson Lands, the last Garry oak ecosystem in Victoria's inner harbour (2018)
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Very little of the original Garry oak landscape remains in an unaltered state. They have declined dramatically in extent over the past two decades, and much of what remains has been strongly modified. There is growing public and scientific concern about preservation of the Garry oak ecosystem. One of several recognized Garry oak vegetation types, the Garry oak - grass community, has been rated as one of the most endangered in British Columbia; other types are rated as threatened.
What is the impact of introduced and invasive species?
Overgrazing by domestic and feral livestock, including pigs, sheep, goats, cattle and horses, as well as introduced eastern cottontail, and recently feral pet rabbits, has caused non-native plant species to become dominant.
These introduced plants spread widely after European settlement. Exotics, such as orchardgrass and sweet vernalgrass may comprise over 30 percent of the total species in Garry oak ecosystems. Rapid spread of Scotch broom has also replaced native plants, changed soil nutrients, and dramatically altered the make-up of these ecosystems. The increased rarity of many native species is another result of these changes.
A new peril to Garry oak is posed by the spread and serious impact of two introduced insect pests: the jumping gall wasp and the oak-leaf phylloxeran. The "scorching" of oaks by these insects results in a potential threat to the ecosystem. Scorched oaks may be mistakenly cut down as "dead," when they are actually still alive.
These introduced plants spread widely after European settlement. Exotics, such as orchardgrass and sweet vernalgrass may comprise over 30 percent of the total species in Garry oak ecosystems. Rapid spread of Scotch broom has also replaced native plants, changed soil nutrients, and dramatically altered the make-up of these ecosystems. The increased rarity of many native species is another result of these changes.
A new peril to Garry oak is posed by the spread and serious impact of two introduced insect pests: the jumping gall wasp and the oak-leaf phylloxeran. The "scorching" of oaks by these insects results in a potential threat to the ecosystem. Scorched oaks may be mistakenly cut down as "dead," when they are actually still alive.
What wildlife species are under threat?
Many invertebrates, including robber flies, butterflies, and seed bugs are restricted to these sunny, coastal meadows. A subspecies of large marbled butterfly is extinct; the perdiccas checkerspot butterfly is no longer found in British Columbia, and Taylor's checkerspot has been reduced to two populations, one of which is on Hornby Island. The propertius dusky wing butterfly is completely dependent on Garry oak (Quercus garryana) for larval growth and is considered a vulnerable species.
Birds are affected too. Lewis' Woodpecker, once a resident of the open, dry woodlands of southern Vancouver Island, disappeared early in the 20th century. Concern is growing for the conservation of a number of other birds for which the ecosystem provides habitat, such as Cooper's Hawk, Western Bluebird, and Band-tailed Pigeon. Nest holes, acorns, and open country habitat are among the attractions which the oak woodlands provide. The rare, little-known, sharp-tailed snake also inhabit this ecosystem.
Birds are affected too. Lewis' Woodpecker, once a resident of the open, dry woodlands of southern Vancouver Island, disappeared early in the 20th century. Concern is growing for the conservation of a number of other birds for which the ecosystem provides habitat, such as Cooper's Hawk, Western Bluebird, and Band-tailed Pigeon. Nest holes, acorns, and open country habitat are among the attractions which the oak woodlands provide. The rare, little-known, sharp-tailed snake also inhabit this ecosystem.
How is our society responding to these concerns?
The value to society of the Garry oak landscape is now being recognized. Victoria City Council adopted a resolution recognizing the historic and ecological significance of the Garry oak ecosystem. Garry oak (Quercus garryana) has been referred to as "our foundation native species." Garry oak is included in the tree preservation bylaws being developed by several municipal councils.
The plight of the ecosystem has been featured in a number of local and national level media stories. Several local development proposals have been opposed by those wishing to save Garry oak landscapes. A colloquium focusing on Garry oak ecosystems, the first of its kind, was held in Victoria in 1993. Three have been held since reflecting increasing concerns over the growing threats to the survival of Garry oak ecosystems. |
A camas meadow in bloom in a restored area of Playfair Park, Saanich (2018)
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Ecological restoration projects, typically dependent on volunteers, are also targeting Garry oak ecosystems. Through invasive species removal and the planting of native species, these damaged ecosystems are being nurtured back to health
Acknowledgements
Some of this material came from the publication "Garry Oak Ecosystems" a pamphlet by W. Erickson, B.C. Ministry of Environment, Lands and Parks, 1993.