Dusky dune moth (Copablepharon longipenne) COSEWIC assessment and status report: chapter 10

Limiting Factors and Threats

The following are limiting factors and threats to Copablepharon longipenne in Canada.

Sand Dune Stabilization

The progressive stabilization of active sand dunes caused by vegetation colonization is considered a serious threat to C. longipenne. This threat affects all C. longipenne populations in Canada.

 

Land and Infrastructure Development

Development activities, such as road building, petroleum infrastructure construction, and excavation of water holes for cattle, which result in direct loss of sand dunes, are considered a threat to C. longipenne. Some types of disturbance associated with development may create habitat for C. longipenne by increasing open sand or initiating dune activity.

 

Population Isolation and Demographic Collapse

Populations of C. longipenne in Canada may be at risk from demographic collapse. Like other species confined to patchy habitats, populations of C. longipenne are spatially isolated. Ecological theory predicts that the risk of a subpopulation going extinct in a single patch (e.g., sand dune) is reduced with increasing numbers of surrounding subpopulations (Hanski, 1982). This risk reduction is caused by the “rescue effect” that allows immigration between patches to prevent the complete collapse of a group of subpopulations. Hugenholtz and Wolfe (2005) documented declines in the number and size of active sand patches in several dune fields including Seward, Great, and Tunstall sand hills. However, the presence of C. longipenne in small and isolated active dunes in Cramersburg and Dundurn sand hills indicates relatively few active dunes are needed to support a population of C. longipenne, although the long-term viability of these isolated populations is uncertain. The conversion of the landscape surrounding sandy habitats and dunes to agriculture may have increased the risk of demographic collapse by reducing opportunities for dispersal

 

Cattle Grazing

Grazing has contradictory effects on C. longipenne habitat. It may initiate active sand movement in dunes and limit colonizing vegetation (Figure 10). Hugenholtz and Wolfe (2005) suggested that recent dune activity in the northwest portion of the Great Sand Hills may be the result of recent drought and grazing stress from livestock. However, grazing may result in soil compaction and browsing of vegetation that is used for larval feeding, and may also crush eggs, larvae, or pupae. It is considered a possible threat to C. longipenne.


Figure 10: Example of the Effects of Cattle Grazing on Sand Dune Habitat

Figure 10. Example of the effects of cattle grazing on sand dune habitat.

The portion of the dune on the right side of the fence is affected by cattle use and shows trail formation, reduced vegetation cover, and substantially greater open sand. The left side of the fence is more stable with higher vegetation cover. Photo from the Straw Roadarea of the Great Sand Hills, SK. Photo by N.A. Page (2005).

 

Recreation

Recreation, including horse riding, ATV riding or off-road vehicle use, and walking or hiking, may be intensive in some sand dunes and result in loss of vegetation and disturbance to sand substrates (Figure 11). It is considered a potential threat to C. longipenne. Recreation is limited to relatively small areas but was pronounced in the Burstall Sand Hills, SK, in accessible dunes in the Straw Road area of the Great Sand Hills, SK, and in the Spirit Dunes near Brandon, MB. It is considered a possible threat to C. longipenne in Canada. Recreation may also maintain or create open sand habitats.


Figure 11: ATV Use in the Burstall Sand Hills has Resulted in Disturbance to Vegetation and Soils

Figure 11. ATV use in the Burstall Sand Hills has resulted in disturbance to vegetation and soils.

 

Research Collecting

Collecting specimens is not considered to be a threat to C. longipenne.


Conservation Concerns in Similar Species

All known Canadian Copablepharon species are associated with dune habitats, which are rare in Canada. Copablepharon grandis Strecker and C. viridisparsa Dod share similar habitats with C. longipenne in the Canadian prairies and are being assessed by COSEWIC (COSEWIC, 2007a; COSEWIC, 2007b). It is noteworthy that one Copablepharon, Copablepharon viridisparsa spp. hopfingeri Franclemont, is the only moth taxon known to have been extirpated from western Canada (Lafontaine and Troubridge, 1998). Historically, it occurred in a small site with sandy soils at Brilliant, BC (near Castlegar). Copablepharon fuscum (Sand-verbena Moth) is the only Copablepharon species west of the Cascade Mountains. It is very rare in southwestern BC (three to five populations) and was designated as Endangered by COSEWIC in 2003 (COSEWIC, 2003). It may be more sensitive to change than C. longipenne because it relies on a single host-plant.

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