Recovery Strategy for the Contorted-pod Evening-primrose (Camissonia contorta) in Canada
The following section is adapted from the species description provided in the status report (COSEWIC 2006).
Habitat destruction and degradation
Although several sites are currently protected in parks, land development constitutes a demonstrated, severe and ongoing threat at several sites across the species range. All plants at Population 6 were destroyed during the development of a golf course on private land, though a small number of plants have since recolonized the area (Table 1). Population 3 is on a Crown land right-of-way belonging to the B.C. Ministry of Transportation and Infrastructure. At this time, there are no development plans for this site (C. Wheeler, pers. comm.).
Recreational use (by pedestrians and vehicles such as all terrain vehicles) constitutes a demonstrated, severe, extensive and ongoing threat to sandy backshore habitats at almost all sites within the Canadian range of Contorted-pod Evening-primrose. There is heavy trampling associated with visitors to some of the sandy backshore habitats where this species occurs (e.g., from hiking, dog-walking, sunbathing and picnicking). Trampling is especially pronounced at Populations 1, 2, 4, 7 and 8. The site that Population 8 occupies has suffered from heavy use by off-road vehicles. Less severe off-road vehicle impacts were also observed at Populations 5 and 6, and there is the potential for damage from off-road vehicles at Population 2 due to its proximity to Population 8, although barriers have recently been erected that are at least partially mitigating the threat from off road vehicles.
Exotic and invasive species: plants
Exotic and invasive plant species constitute a demonstrated, severe and ongoing threat. A number of exotic and invasive species have invaded habitats favoured by Contorted-pod Evening-primrose, especially at Populations 5 and 7.
The exotic and invasive Scotch Broom (Cytisus scoparius) is present immediately adjacent to or within all eight extant populations. It competes for space with Contorted-pod Evening-primrose. It also shades sites during part of the day and may gradually stabilize semi-active sand areas by forming dense thickets. This will facilitate succession and eliminate open habitats.
Other exotic and invasive species that pose a serious threat at one or more sites include Crow Garlic (Allium vineale), an aggressive onion, which is spreading rapidly in areas where it has become established (especially at Population 5), and European Beachgrass (Ammophila arenaria), which tends to stabilize dunes and thereby alter substrate dynamics, especially at Population 7. A portion of Population 7 appears to have been lost, likely as a result of invasion by Scotch Broom and European Beachgrass (M. Fairbarns, pers. obs.). This population is already at low numbers, so further loss is a significant threat to its persistence. Other exotic species that occur in the vicinity of Contorted-pod Evening-primrose and pose a potential threat include grasses such as Early Hairgrass (Aira praecox), Silver Hairgrass (A. caryophyllea), Cheatgrass (Bromus tectorum), Soft Brome (B. hordeaceus), Ripgut Brome (B. rigidus), Rattail Fescue (Vulpia myurus) and Barren Fescue (Vulpia bromoides). Frequent non-native forbs include Sheep Sorrel (Rumex acetosella), Sticky Chickweed (Cerastium glomeratum), Hairy Hawkbit (Leontodon taraxacoides), Hairy Cat’s-ear (Hypochaeris radicata) and Stork’s-bill (Erodium cicutarium).
Exotic and invasive species: animals
Herbivory by non-native animals constitutes a possible, minor and ongoing threat. Plants in Populations 1, 2, 5 and 7 have experienced light to moderate levels of herbivory (M. Fairbarns, pers. obs.). It is assumed that this herbivory is from Eastern Cottontails (Sylvilagus floridanus), as rabbit droppings are abundant at most of these sites as well as in the location that Population 8 occupies. However, the impact of rabbit grazing on competing vegetation, which is quite evident, may offset the minor impacts of grazing on Contorted-pod Evening-primrose.
Climate change is seen as an emerging threat, but one that has unknown consequences for Contorted-pod Evening-primrose. Sea level changes and alterations to rainfall patterns could have implications for this species.
The overall aim of this recovery strategy (for the period 2011 to 2020) is to attain nine viable populations of Contorted-pod Evening-primrose in Canada. To meet this aim, this recovery strategy has four population and distribution objectives. Objectives are not listed in order of priority (see Table 4 for prioritization of recommended activities).
- Maintain the known extent of occurrence for the species in Canada (by 2015).
- Maintain population sizes for all extant locations at current or higher levels (by 2015).
- Ensure all eight extant populations reach, and are maintained at, no less than their minimum viable population size (by 2020).
- Establish one additional population (to replace the single known extirpated population) at a site with suitable habitat within the known range of the species in Canada, and maintain it at no less than its minimum viable population size (by 2020).
A report on proposed management actions for Capital Regional District (CRD) Parks (Populations 1 and 2) has been prepared (Fairbarns 2004). Eighteen recommendations were made, including the following four key points:
- Improve the conservation of the existing populations of Contorted-pod Evening-primrose in CRD Parks.
- Encourage awareness of conservation values, with an emphasis on plant species at risk.
- Monitor the populations of rare sand dwelling plants as well as their habitat and park use.
- Restore degraded habitat and encourage the establishment of new subpopulations of Contorted-pod Evening-primrose or expansion of existing ones.
CRD Parks began implementation of management recommendations in 2007, with the establishment of a fence and signage to reduce traffic in the habitat occupied by Population 2. Regrettably, there is still evidence of frequent, heavy trampling by people climbing over the fence (Fairbarns, pers. obs., 2008). No recovery actions recommended for this species have been implemented for Population 1.
CRD Parks, the Municipality of Central Saanich, and the Tsawout First Nation are currently developing a management plan for an area that includes all sandy habitats stretching from Population 2 to Population 8. This project includes habitat mapping, rare species mapping and development of a coordinated access management plan both for walkers and off-road vehicle users. At Population 8, concrete barriers, fencing and signage have been utilized south of Cordova Spit Municipal Park on Tsawout First Nation lands to protect and inform visitors of this fragile ecosystem.
The private landowner whose property includes Populations 5 and 6 has instituted a conservation covenant under Sec. 219 of the B.C. Land Titles Act for all of Population 5 and part of the original location of Population 6. The covenant is monitored by the Nature Conservancy of Canada and restricts most access to the site. The Nature Conservancy of Canada is currently planning for the restoration of Population 5.
Table 4 outlines the detailed approaches recommended for recovery of Contorted-pod Evening-primrose. Each approach relates to one or more of the population and distribution objectives.
2 Currently, there are nine known populations. The number of populations should therefore be recovered to at least this number. The actual number of populations that occurred historically cannot be determined with certainty at this time. The target of nine populations will be reconsidered at the action plan stage once further surveys and analyses of potential habitat have been completed (see research approaches listed in Table 4).
3 Known extent of occurrence = the extent of occurrence of the combined 8 known extant and 1 extirpated populations. Historical extent of occurrence is currently unknown.
5 Minimum viable population size cannot currently be identified with certainty, but see Section 1.4.1 for current knowledge and Table 4 for further recommendations towards development of a specific target population size that will ensure viability for each location.
6 The objective to establish only one new site may change at the action plan stage if further analyses suggest there were more than nine historical populations in Canada.
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