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Garry oak Ecosystem

Garry oak and deer
Detail from Garry oak Ecosystem
Garry oak Ecosystem
Garry oak over the garden
Invasive species / Garry oak Ecosystem

Garry Oak Ecosystem

Vancouver Island Habitat

Apart from a few small, isolated patches near Hope, BC, the Garry Oak ecosystem ranging from Nanaimo to Sooke is the only substantial habitat of its kind remaining in Canada. The foundation of these systems, the Garry Oak, is not listed as a threatened species in BC, but it is estimated only 5% of the area once covered is remaining. The plant and animal assemblage surrounding these trees is unique, with more plant species present in this ecosystem than in any other in BC. As well, the Garry Oaks support more than 100 species of birds, 7 amphibians, 7 reptiles, and 33 mammals, making them an invaluable part of Vancouver Island’s biological landscape.


Location and Access

Coordinates: (Southeast Coast of Vancouver Island)

The Garry oak ecosystem (GOE) follows the southeast coast of Vancouver Island from Comox Valley to Sooke, including the Gulf Islands, generally staying within fifteen kilometers of the ocean. Once covering most of the region, the GOE now only covers 5% of its original territory, primarily due to dense human settlement of this area. Several areas are set aside specifically for the preservation of the GOEs, including Mt. Tolmie in Victoria, Mt. Maxwell on Saltspring Island, and Mt. Tzuhalem in the Cowichan Valley, but many more are not protected, and are in danger of being destroyed or encroached on by human activity.

There are no regulations concerning the access to the ecosystems, though any that fall inside park boundaries are subject to the park’s rules, and many of the remaining trees fall on private property.


Description


The GOEs are situated in the hottest, driest parts of Vancouver Island, and as they are suited to this climate, they outcompete the local dominant evergreens. In an original, undisturbed state, the GOE exists in two forms. The shallow soil scrub-oak sites are the most common, with over 44% of the original cover remaining, but are also the least biodiverse of the two. They are characterized by a rocky subsoil composition, with a thin layer of dry soil on top, and have mostly grasses and mosses as an understory. The deep soil sites are more complex, allowing an understory with shrubs, small trees, long grasses, and flowers to grow. These sites tend to be level, without rocky outcroppings and unfortunately, only about 1.5% of the deep soil sites remain.


Life in the Garry oak Ecosystem:


Though named after the Garry oak tree, the GOEs are just as much about the hundreds of other species making the area home. More plant species associate in these ecosystems than do in any other area of British Columbia, and their relatively open canopy results in an incredible diversity of life at the ground level. There are far too many species to list that live in the GOE, but a selected number are at extreme risk of extirpation or extinction. Victoria meadow-clover, deltoid balsamroot, white-top aster, small-flowered tonella, Howell’s tritelia, and yellow montane violet all are earmarked for special status in the GOE due to their rarity or endemism.

Generally, an undisturbed GOE is a wide meadow-like clearing with plenty of sun reaching the ground. Seasonal fires are thought to have been a factor in preserving the GOE in its natural state, as the oaks are fire resistant, and the invading Douglas fir seedlings are not. This would also clear out the undergrowth, preserving the meadow-like state of the area the following years. With the suppression of these fires due to human settlement, the coniferous forest is reclaiming some of the GOE at its edges.

The GOE also supports a vast community of animals native to the region, and provides crucial habitat for many vulnerable species. Designated as “at-risk” are seven species of butterflies, as well as the western meadowlark, western bluebird, vesper sparrow, Lewis’ woodpecker, streaked horned lark, and sharp-tailed snake.

 

Web site ©: The Institute for Coastal and Oceans Research (ICOR) at the University of Victoria, British Columbia Canada.