Area: 0.61 hectares.
This site is notified for the presence of important populations of an internationally very rare liverwort, western rustwort Marsupella profunda.
The three discrete parts of this site are all located within the St Austell china clay district to the north of St. Austell. They are underlain by the Upper Carboniferous St Austell Granite, which is part of the Cornubian batholith. Zones within the granite, altered by kaolinisation, have been extensively worked for china clay. All three areas are located within currently active china clay workings consisting of pits, spoil tips and granitic debris with sparse vegetation cover.
The site supports important populations of the internationally rare liverwort western rustwort Marsupella profunda. The UK distribution of this species is restricted to china clay workings within the St Austell china clay district in east Cornwall and, former clay workings in west Cornwall at Tregonning Hill, Lower Bostraze, and Leswidden. Internationally, western rustwort is rare throughout its range, it appears to have a restricted, strongly oceanic range, with records from Portugal, Madeira, and the Azores. In recognition of its rarity and vulnerability western rustwort is protected under UK and European Union legislation.
In the St. Austell Clay Pits, western rustwort is generally found growing on micaceous or clay waste substrates which are flat or gently sloping. Some patches occur on granitic rocks, usually where these are soft or crumbling. Western rustwort is a pioneer species, the largest populations being found on surfaces showing the early stages of colonisation by other bryophytes and by vascular plants.
This is a new site. In recognition of its national and international importance western rustwort Marsupella profunda is listed on:
· Schedule 8 of the Wildlife and Countryside Act 1981 as amended.
· Annexes II & IV of the European Community Habitats and Species Directive 1992 as a 'priority' species. (It is the only Annex II 'priority' species listed which occurs in Britain.).
· Appendix I of the Bern Convention.
· Priority Species in the UK Biodiversity Action Plan 1995. (In which it is classed as Critically Endangered in Britain).