BC Conservation Data Centre: Conservation Status Report
Sabulina pusilla
dwarf sandwort
| Scientific Name: | Sabulina pusilla |
|---|---|
| Scientific Name Synonyms: |
Arenaria pusilla
Minuartia pusilla |
| English Name: | dwarf sandwort |
| Provincial Status Summary | |
| Status: | S1 |
| Date Status Assigned: | April 30, 1996 |
| Date Last Reviewed: | April 30, 2019 |
| Reasons: | Minuartia pusilla has a small effective population size, has an extremely limited range and occupied area, and has substantial non-imminent threats. |
| Range | |
| Range Extent: | A = <100 square km |
| Range Extent Comments: | There is a single occurrence at Rocky Point, on southern Vancouver Island, in the lowland zone (CDFmm). |
| Area of Occupancy (km2): | AC = 1-5 |
| Area of Occupancy Comments: | This population only occupies about 10 square meters. |
| Occurrences & Population | |
| Number of Occurrences: | A = 1 - 5 |
| Comments: | Only one verified extant occurrence. |
| Number of Occurrences with Good Viability / Ecological Integrity: | AB = 0 - 3 |
| Comments: | It is unknown if the single population has good viability. |
| Number of Occurrences Appropriately Protected & Managed: | U = Unknown |
| Comments: |
The occurrence is on Department of National Defense lands where public access is restricted. The area in which M. pusilla occurs is currently used as a buffer and training area (for small patrols carrying out map and compass work) with no foreseeable alternate use into the future (A. Robinson, pers. comm.). A natural resource management program for these D.N.D. properties is going to be implemented. The plan includes recommendations from the science advisory committee, a group that oversees research on the lands. Rare plant demographic studies and mapping are currently part of the research program. Locations of all rare plant species are going to be identified on a sensitive sites map for the properties so that they can be better protected (A. Robinson, pers. comm.). |
| Population Size: | B = 50 - 250 individuals |
| Comments: | There were about 120 plants in April 2003. |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Substantial, non-imminent threat |
| Comments: |
Any random unexpected disturbances that could damage the 10 square meters of habitat at the single known site for this species pose an imminent threat. Minuartia pusilla is likely quite sensitive to physical disturbance due to its diminutive stature and susceptible to any physical or chemical changes to the vernal seep it inhabits. Actual threats include digging by gulls and possibly trampling by trespassing boaters. In the winter of 2002 to 2003, soils were moderately churned up by gulls in the immediate vicinity of M. pusilla. Light disturbance likely helps limit pre-emption by mosses and other annuals. It is not known to what degree M. pusilla is able to compete with other annual species such as Vulpia spp. Competition could become a limiting factor. Minuartia pusilla also likely experiences demographic fluctuations as a result of natural but irregular and limited winter rains. It is possible that the species could disappear altogether if critical moisture is not available for germination and seedling development, and is therefore potentially susceptible to climate change (i.e. drying trends). Likewise, if conditions are too wet, the habitat will be unsuitable. |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | G = Relatively Stable (<=10% change) |
| Comments: | Probably stable; first observed in 1977, but only seen on about three occasions since, so trends are not well known. |
| Long-Term Trend: | U = Unknown |
| Other Factors | |
| Intrinsic Vulnerability: | B=Moderately vulnerable |
| Comments: | Minuartia pusilla is an ephemeral species and therefore, relies on seasonal precipitation for germination and longevity (Meinke and Zika 1992). It is dependent on consistent year-to-year moisture during the appropriate seasons for both germination and seedling development. We do not know how adaptable the species will be to climate change (i.e. to an increasing drying trend), but it is likely that it will not survive, due to these requirements. |
| Environmental Specificity: | A=Very narrow. Specialist or community with key requirements scarce. |
| Comments: | Minuartia pusilla occurs in a vernal seepage area. In BC, it only occurs in the special moisture conditions that are characteristic of this habitat type. |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | In order to assess order of magnitude population fluctuation in annuals like Minuartia pusilla which likely fluctuate greatly from year to year due to annual variations in available moisture, one will have to monitor annual fluctuation over several years. Severe drops and spikes should be looked at in terms of importance to long-term survival. A severe enough drop could result in the loss of the species from the site whereas spikes in the population could represent an important time for replenishment for the population. |
| Inventory Needs: | Adolf and Oluna Ceska searched for this species in a number of sites in 2002 without success- Gonzales Hill, Uplands Park, Mount Tolmie, Albert Head, Dallas road, Victoria, Nanoose, Golf Hill and Hornby Island. A similar effort should probably be repeated some time in the future to ensure that this species has not been over-looked in other sites (perhaps following a particularly wet winter/spring). |
| Stewardship | |
| Protection: | Since there is only one known site for this species in BC (and Canada), it is imperative that that one site be protected. |
| Management: | It is important that the continued persistence of Minuartia pusilla and other rare plants at Rocky Point are incorporated into the DND natural resource management plan. |
| Version | |
| Author: | J.L. Penny |
| Date: | October 01, 2003 |
| References | |
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COSEWIC. 2004j. COSEWIC assessment and status report on the dwarf sandwort Minuartia pusilla in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 17 pp.
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Parks Canada Agency. 2006. Recovery Strategy for Multi-species at Risk in Vernal Pools and Other Ephemeral Wet Areas in Garry Oak and Associated Ecosystems in Canada. Species at Risk Act Recovery Strategy Series. Ottawa: Parks Canada Agency. 73 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. 2003. Conservation Status Report: Sabulina pusilla. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 8, 2026).