BC Conservation Data Centre: Conservation Status Report
Anarta edwardsii
Edwards' Beach Moth
| Scientific Name: | Anarta edwardsii |
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| English Name: | Edwards' Beach Moth |
| Provincial Status Summary | |
| Status: | S1 |
| Date Status Assigned: | July 28, 2009 |
| Date Last Reviewed: | March 15, 2020 |
| Reasons: | There are only 2 known populations of A. edwardsii in BC. The sparsely vegetated, sand-dominated coastal sites that it requires are regionally rare and at risk from succesion, invasive species, and other factors. The calculated area of occupancy of this species is 20 square km at the most. |
| Range | |
| Range Extent: | D = 1,000-5,000 square km |
| Range Extent Comments: | Post 1990 records include Pacific Rim National Park on the west coast and the Saanich Peninsula and 2 Gulf Islands (James and Sidney Island) on the east coast. The range extent in BC/Canada is estimated at 2050 square km (COSEWIC 2009). |
| Area of Occupancy (km2): | C = 3-5 |
| Area of Occupancy Comments: | The area of occupancy using the 2X grid method is 20 square km for the last 15 years. Suitable habitat within this area is limited to about 10% (COSEWIC 2009). The area of occupancy is 16 square km if looking at only the last 10 years; and 28 square km if historical records are included (COSEWIC 2009). |
| Occurrences & Population | |
| Number of Occurrences: | A = 1 - 5 |
| Comments: | Collections have been made from seven locations, making up two populations or occurrences. One population is in Pacific Rim National Park and the other population is comprised of six locations found on the Saanich Peninsula (Southern Vancouver Island) and the adjacent Gulf Islands (James and Sydney Islands). Populations are determined based on the distances that seperate known locations in accordance to the definition of location given by COSEWIC (2009) and NatureServe standards. Known historic localities include Thetis Island and Mill Bay on the Saanich Inlet (COSEWIC 2009). |
| Number of Occurrences with Good Viability / Ecological Integrity: | U = Unknown |
| Number of Occurrences Appropriately Protected & Managed: | A = None |
| Comments: | A. edwardsii is not specifically protected. One population is within the Pacific Rim National Park and so is under the general protection afforded to wildlife in National Parks. Localities of the other population are on Sidney Island which is part of the Southern Gulf Islands National Park Reserve; within smaller areas in Regional and Municipal Park; First Nations land; and private land (COSEWIC 2009). The locations within parks may afford some habitat protection. |
| Population Size: | U = Unknown |
| Comments: | No quantitative information on population sizes. Recent sampling indicates it can be locally abundant in suitable habitat (COSEWIC 2009). |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | AB = Very high - high |
| Comments: |
The primary threat to A. edwardsii is loss or degradation of sparsely-vegetated sandy beach habitats from natural or anthropogenic disturbance. Invasive Non-Native/Alien Species are a direct threat as the progressive loss of open sand habitats from vegetation stabilization of sand dunes is the primary cause of habitat decline. The introduction of invasive exotic plants, especially Cytisus scoparius (Scotch broom) as well as a variety of exotic grasses (e.g., Bromus tectorum, Ammophila arenaria, Dactylis glomerata, Holcus lanatus, Bromus hordeaceus, Vulpia myuros, Anthoxanthum odoratum) have accelerated stabilization. Native mosses function in concert with vascular plants rapidly colonizing the sand surface. It is considered a severe threat at all locations (COSEWIC 2009). Climate Change and Severe Weather causing Habitat Shifting and Alterations is another potential threat as sea-level rise could threaten habitat directly. Sand spits and dunes are particularly prone to loss when sea level rise is accompanied by storms of increased frequency and intensity. However, these same storms may have a positive effect if they result in increased development of open sand habitats due to accelerated coastal disturbance and sediment transport that is associated with them (COSEWIC 2009). Other threats that are more restricted in scope are Residential and Commercial Development (shoreline armoring, building of golf courses, trails and buildings) and Human Intrusions and Disturbance due to Recreational Activities such as the trampling or destruction of host plants or the compacting of sand substrates by ATVs or hikers (COSEWIC 2009). |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | F = Decline of 10-30% |
| Comments: | Antrhopogenic and natural habitat loss has resulted in declines in the extent of occurrence and area of occupancy since 1994 and has likely resulted in minor population declines as well (e.g. A. edwardsii has not been found at Cordova Spit and Island View Beach since 1994/1995 despite more recent searches), (COSEWIC 2009). |
| Long-Term Trend: | E = Decline of 30-50% |
| Comments: |
Over the past 100 years sand-dominated coastal sites in BC have been rapidly and extensively changed throughout the range of C. fuscum, a related noctuid moth with similar sand habitat requirements (COSEWIC 2009). The loss of open dune habitat over the last 40+ years was 50% at the 2 sites near Comox and 21% at the Island View Beach/Cordova Spit site (COSEWIC 2003). The Mill Bay locality is believed no longer extant as surveys conducted between 2001-2007 did not find the moth. Records from Thetis Island are all pre-1975, and this population may no longer be extant (COSEWIC 2009). It has not been sampled for since this time. |
| Other Factors | |
| Intrinsic Vulnerability: | B=Moderately vulnerable |
| Comments: | Existing populations in BC are spatially-isolated. It is unknown if A. edwardsii populations depend on regular dispersal for persistence or if they are stable remnants (COSEWIC 2009). |
| Environmental Specificity: | B=Narrow. Specialist or community with key requirements common. |
| Comments: | The sparsely vegetated, sand-dominated coastal sites that A. edwardsii requires are regionally rare. The larval host plant(s) is unknown in Canada therefore it is unknown if this is a limiting factor as well (COSEWIC 2009). |
| Other Rank Considerations: | Rescue Effect: It may be possible for there to be some dispersal between the population in the San Juan Islands in Washington State, US (located on Henry Island approximately 12 km across open water). Recolonization from populations outside of BC might be possible, but would not be extensive (COSEWIC 2009). |
| Information Gaps | |
| Research Needs: | More studies on the general biology of A. edwardsii are required as there is no information on its reproduction, survival, physiology (e.g. growth and dormancy) and dispersal abililties in Canada. A better understanding of its specific habitat requirements is needed including determinng its larval host plant(s). |
| Inventory Needs: | Thetis Island needs to be surveyed as last records are pre-1975. Cordova Spit and Island View Beach should be re-inventoried as it had been found in 1994/1995, although more recent searches have not led to new records (COSEWIC 2009). Additional inventory is required in suitable habitat that has not yet been surveyed. |
| Stewardship | |
| Protection: | |
| Management: | Control of invasive exotic plant species such as Scotch broom may help to reduce the loss of sand/dune habitat due to vegetation stabilization. |
| Version | |
| Author: | Westereng, L.K. |
| Date: | August 28, 2009 |
| References | |
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COSEWIC, 2009. COSEWIC status report on Anarta edwardsii (Edwards' Beach Moth) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. iv+25pp.
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COSEWIC. 2003x. COSEWIC assesment and status report on the sand-verbena moth Copablepharon fuscum in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii+31 pp.
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Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 2009. Conservation Status Report: Anarta edwardsii. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 5, 2026).