Stoloniferous pussytoes (Antennaria flagellaris) COSEWIC assessment and status report: chapter 8
Limiting Factors and Threats
In general, only 2% of BC grassland areas had protected status in 1992 (The Land Conservancy of BC 2002); however grassland and open forest habitats are threatened by a number of factors. Development pressure from the expanding population, habitat fragmentation, degradation due to weed invasion, and off-road vehicle activity have been identified as threats (BC WLAP 2002).
The most imminent threat to the populations of Antennaria flagellaris is their vulnerability to extirpation due to their small, occupied area (ca. 0.22 hectares). Such geographically restricted populations aremore vulnerable to demographic and environmental variation and loss of genetic variability (Primack 1998). Since suitable habitats for A. flagellaris are also extremely restricted the opportunities for colonization and expansion are also limited.
The potential habitat of A. flagellaris, the open eroded slopes within the Roany soil series, is extremely restricted. Even within the area (1750 ha) mapped as Roany soil series, there are sizable pockets of two other series (Belfort and Lamont). These occupy 40% or 700 ha of the Roany soils series area. In addition, Roany soil series support large amounts of open Pinus ponderosa forests or Artemisis tridentata shrublands (Green and Lord 1979), thus suitable habitat is further limited.
Another threat that is likely to have an impact is recreational off-road vehicles use. The authors observed evidence of ATV and dirt bike use in the immediate area of the sites in 2002. In fact, there was evidence of it throughout the area and even as close several metres at the most northern site. These vehicles have easy access to the area since fences only occur to the south. Due to the nature of the steep, clay slopes where A. flagellaris occurs, habitats could easily be modified by this activity. When moist, this habitat would be highly susceptible to disturbance, and at the same time, be at its most desirable to off-road users. Overuse of the habitat in this way could disturb the sites enough to radically alter the substrate, and promote the establishment of non-native species. Once ruts are created, especially across the slopes, organic debris accumulates and slope soil movement or soil moisture regimes are likely to be disrupted and become more favorable to non-native species.
The private properties where A. flagellaris occurs are in the Agricultural Land Reserve (ALR), where primary land use is agriculture. On these lands, development pressures may not appear to be an issue at this time. There have been no applications to have the private properties taken out of the ALR for development thus far (Wallace, pers. com., 2003), but landowners may decide to apply in the future. The success of these applications would be enhanced on the Roany soils series where A. flagellaris occurs since “steep slopes and lack of water for irrigation limit use of roany soils for agriculture. The shallow soil and the slow permeability of the underlying materials cause these soils to erode readily” (Green and Lord 1979). Furthermore, housing sales have trended upwards in the last 12-18 months in the Princeton area in tandem with markets in the Okanagan Valley (Fabri, pers. com., 2003). The Antennaria flagellaris locations are only within five kilometers of the town of Princeton. The first author has observed that i n recent years many tracts of ALR land in southern British Columbia have been converted to housing developments, shopping malls and golf courses, either by decisions of the Agricultural Land Commission or very rarely by an 'order in council' by the sitting provincial legislature.
Even if the ALR status currently prevents subdivision development, activities that are allowable in the ALR could also potentially threaten the populations. For instance, some types of fill/soil removal are allowable without application to the Agricultural Land Commission (Provincial Agricultural Land Commission 2003). Any developments that even slightly change groundwater levels could be devastating to this taxon.
Another potential threat is weed control activities. Marginally specific chemical weed control substances that kill broad-leaved plant species would likely kill A. flagellaris. The populations occur within 50-150 m of the power line right-of-ways which presents a significant problem in terms of weed control.
The potential development of coalbed methane from deposits underlying the region around Princeton potentially could have significant impacts on surface habitats and ground water hydrology.
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