Yellow montane violet (Viola praemorsa) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

In British Columbia, yellow montane violet occurs in Garry oak woodlands and maritime meadows. These low-elevation (< 30 m), herb-dominated ecosystems are largely confined to coastal situations (within 3 km of the shoreline) along south-eastern Vancouver Island and a subset of islands in the Straight of Georgia, Haro Strait and the Strait of Juan de Fuca. Summer and winter temperatures are greatly moderated by proximity to the ocean. Maritime meadows and Garry oak woodlands may be largely free of shrubby vegetation for a variety of reasons, including strong summer moisture deficits (particularly on wind-exposed sites and/or those with thin, coarse-textured soils), salt spray and a long history of First Nations burning. These forces may act alone or in concert, consequently some Garry oak woodlands and maritime meadows are subject to forest ingrowth while others remain open despite fire suppression (Parks Canada Agency 2006). Most microhabitats occupied by yellow montane violet have shallow soils over bedrock, are relatively level or south-facing, have little or no shrub cover and have an abundant cover of herbaceous species. In spring, the herb layer is dominated by native forbs such as Camassia quamash and Sanicula crassicaulis. In summer, the native herbaceous layer is replaced by a diverse assemblage of forbs and grasses.

Habitat trends

The amount of potential habitat has declined greatly over the past century as coastal areas in southeast Vancouver Island have been developed for residential and recreational use. Less than 1% of the Coastal Douglas-fir biogeoclimatic zone remains in a relatively undisturbed state (Pacific Marine Heritage Legacy 1996). Garry oak ecosystems in the Victoria region have declined from 10,510 ha in 1800 to 512 ha in 1997 (Lea 2002); even more has been lost since then, and most of what remains has been heavily altered through invasion by exotic grasses and shrubs. The remaining Garry oak ecosystems persist largely as isolated communities that are heavily fragmented and lack connections that would allow substantial genetic interchange. Habitats suitable for yellow montane violet have probably suffered proportional declines in area and quality.

The distribution of yellow montane violet in British Columbia lies at the heart of one of North America’s fastest growing regions, near Victoria British Columbia. The population of metropolitan Victoria has increased from approximately 180,000 in 1966 to 338,738 in 2005 and is projected to increase to 407,600 by 2026 (CRD 2006). The population of the Cowichan Valley Regional District, where the majority of the Canadian population occurs, grew by 16% between 1991 and 2001 (Cowichan Region Economic Development Commission 2001). This growth was concentrated in the eastern portion of the district, the only portion with suitable habitat for yellow montane violet.

Populations at the Saanich 3, Saanich 6 and Nanoose sites (see Table 1) have been lost to property development. The two Saanich populations probably disappeared before 1980; the population at Nanoose disappeared between 1973 and 1976. Most of the remaining populations are secure from development, at least over the next 10 years. The exception is Saanich 7 which occurs on an undeveloped private lot with an attractive view overlooking Victoria and the Sooke Hills and therefore has high development potential.

Protection/ownership

Of the 14 extant populations in Canada, seven are in municipal and/or regional parks where they are protected from development but face major threats from park users. Three populations are in provincial parks and ecological reserves where they receive legal protection, and where recreational activities tend to be less intensive. Two populations are in private conservancies and receive a high degree of protection involving measures to control invasive species and counteract the impacts of fire exclusion. The two remaining sites are not protected (Table 1).

One extirpated population (Nanoose) may have occurred on or near federal lands. One extant population (Saltspring 2) extends onto federal lands.

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