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COSEWIC assessment and status report on the contorted-pod evening-primrose (Camissonia contorta) in Canada

Habitat

Habitat requirements

Camissonia contorta is a habitat specialist, restricted to dry, open, sandy areas throughout its range. It has been found in sparsely vegetated open areas, grasslands, chaparral and woodlands. In the Pacific Northwest it is restricted to low elevations but in California it occurs up to 2300 m (Peck 1941; Hitchcock and Cronquist 1961; Raven 1969; Atkinson and Sharpe 1993; Wagner 1993).

In Canada, Camissonia contorta has even more specialized habitat requirements. Here, it is restricted to semi-stable sandy flats and dunes no more than 15 m above sea level. It occurs on five level sites near Victoria (populations 1, 2, 5, 6, and 7) and south-facing slopes of up to 50% on Savary Island (populations 4 and 5). All seven extant populations occur on sites that are xeric and rapidly drained, withplenty of bare sand and little or no surface organic material or rock. The sites have negligible tree or shrub cover, although Scotch broom (Cytisus scoparius)sometimes grows nearby and shades sites during part of the day. Camissonia contorta tends to occupy sparsely vegetated sites and is absent from areas where there is a high cover of grasses and forbs. It is scarce or absent from continuous carpets of mosses such as Racomitrium canescens, Tortula princeps and Polytrichum piliferum which often grow at the edges of populations. It can tolerate light levels of sand erosion and deposition and may require such disturbances in order to escape competition. It is absent from more active areas of sand dunes and other sites with unvegetated sand.

Such habitats are highly fragmented within its extent of occurrence in Canada. The fragmentation is fundamentally due to the natural distribution of shoreline sand deposits although this has been exacerbated by residential and tourist development in many fragments which were once suitable. Contemporary and historical records indicate Camissonia contorta is naturally infrequent and even among fragments of suitable habitat, it only occupies small patches.

Habitat trends

There is no quantitative information on the overall decline in quality and extent of sand dune and beach locations on southeastern Vancouver Island and the adjacent Gulf Islands. There is considerable anecdotal and qualitative information documenting a rather serious trend of habitat degradation(see subsequent section on limiting factors and threats).

At the Saanich C population, however, scattered patches of Camissonia contorta are found in fragments of intact habitat throughout recently roughed-in fairways of a 40,000 proposed golf course extension. The roughed-in fairways have been heavily altered and it appears the existing population is a remnant of a once-continuous and far more abundant population. An adjacent 140,000 m² area of former sand-plain was developed into groomed fairways more than a decade ago. Camissonia contorta probably once occurred on much of this area as well. It thus appears that suitable habitat for the species at Saanich C has declined by more than 75% over the past few decadesand that population numbers in the remaining roughed-in fairway have declined by more than 50% over the past decade.

Habitat protection/ownership

Populations 1 and 2 occur within Capital Regional District Parks. The habitat is protected by policies laid out in a general master plan for all parklands administered by the agency (Capital Regional District Parks 2000). In reality, both populations occupy habitat which that receives moderate to high foot traffic by park visitors. Rustic trails have been laid out in the vicinity of population 2 and these serve to reduce the amount of foot traffic that might otherwise affect the population. Capital Regional District Parks has indicated an interest in developing and implementing measures to protect both populations.

Populations 3 and 4 are on a right-of-way belonging to BC Ministry of Transportation. That agency has not developed legislation or policies with respect to species at risk or the habitats they occupy (Greg Czernick, pers. comm. 2004). The Province of BC has no legislation protecting Camissonia contorta habitat on provincial lands.

Populations 5 and 6 occur on private land managed for recreational use. Most or all of population 6 occurs on roughed in fairways of a proposed golf development.

Population 7 occurs in Gulf Islands National Park Reserve and is protected by federal legislation, however the population is threatened by invasive shrubs and, to a lesser degree, by visitor activities.

The extirpated population occurred on municipal parklands at Cordova Spit. This park, which is accessible by boat or through Indian Reserve lands, receives little or no management from the municipality. There is no current master-plan for this site, or for Central Saanich Parks in general. Instead, management is guided by the Official Community Plan (Hope Burns, pers. comm. 2004). This policy document encourages the maintenance of natural erosion and deposition processes that maintain beach environments. It also encourages the conservation of rare, threatened or endangered ecosystems and species. It does not indicate what priority natural history values, or rare species occurrences in particular, should have when resolving conflicting land use interests. These parklands on Cordova Spit, which also contain a number of other rare species, experience moderate to heavy ATV use as well as cultural and recreational activities. Over the past decade there has been a significant increase in the area destabilized by vehicle ruts. Such activities almost certainly led to the extirpation of the population which that was last seen in 2002 (Adolf Ceska pers. comm. 2004)