Assessment Rationale:

Geomitra tiarella was listed in 1994, based on a very restricted range, and when the new Categories and Criteria were introduced in 1996, the species maintained the Endangered status on the basis of limited area of occupancy, number of sites and declining habitat quality. The species is still only known from a small area of occupancy, with four locations along the coastal cliffs and is still viewed as susceptible to habitat degradation on the areas adjacent to the main road and hence it is assessed at Endangered (EN) B1ab(iii)+2ab(iii).

Geographic Range:

This species is endemic to Madeira, where it can still be found living on the north coast of Madeira between Sao Vincente and Porto Moniz (Seddon 2008). Wollaston (1878) commented on the low numbers of specimens found, with the most abundant finds of 120 shells just east of Sao Vincente; this pattern remains today (M. Seddon pers. comm. 2010). It was abundant in the Quaternary fossil deposits at Canical.

Population:

This species has always been rare in samples but was recorded by Seddon (2008) and by Cameron and Cook (1998).

Habitat and Ecology

This species is found on coastal cliffs and steep slopes, amongst short turfed grasses and herbs and amongst leaf-litter on rock ledges. It is also present on rock surfaces on cliffs.

Major Threat(s):

The major threats come from habitat degradation due to presence of roads and tunnels along this part of the coast, with possibility of road widening, pollution from run-off from the road. Also introduction of non-native plants and molluscs to the habitat.

Conservation Actions

This species is listed on the EU Species and Habitats Directive requiring designation of a protected area (pSAC). At present there are no known conservation action plans for this species, and at present the main part of the range does not fall into a protected area. Invasive species need to be controlled, more research is required on the population and distribution of this species, as well as monitoring of its habitat.