Dwarf sandwort (Minuartia pusilla) COSEWIC assessment and status report: chapter 8

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Limiting Factors and Threats

Any random unexpected disturbances that could damage the 10 m² of habitat at the one 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.