Results of a survey to monitor the EU Annex I habitat Calaminarian grassland, 2018

Abstract

Calaminarian grasslands of the Violetalia calaminariae (Natura code 6130) are listed on Annex I of the EU Habitats directive, obligating member states to report on the condition of this habitat at regular intervals, under Article 17 of the directive. This survey reports on the status and condition of 29 sites previously identified as containing Calaminarian grassland, and defines a monitoring methodology to be applied across these sites. Calaminarian grassland is a habitat that occurs on metalliferous substrates, in Ireland occurring only on spoil artificially derived from mining activity. Its presence in Ireland is indicated by the presence of metalliferous bryophyte (moss and liverwort) and vascular plant species, with a suite of rare bryophytes present in this habitat that are of high conservation value and are not found in other habitats. One moss species of this habitat, Ditrichum cornubicum, is of particular conservation importance, as it is only known worldwide to occur at three locations, one of which is in Ireland. The results from this survey show that the Calaminarian grassland is undergoing a continuing decline, as the toxicity of the spoil exposed by mining activities decreases over time. This is leading to succession to other habitats, particularly scrub, heath and acid grassland, and the loss of Calaminarian grassland habitat and populations of the species that require this habitat to survive. As most old mine sites are considered to be marginal land, human activities are also impacting this habitat, with pollution, land reclamation and recreational and agricultural activities negatively impacting many sites. It was calculated that 6.2 ha of Calaminarian grassland occurs within the sites surveyed, which differs greatly from the previous survey of 2008, when a figure of 13.6 ha was estimated. This difference is due to more accurate methodology being used for this survey, and does not represent a dramatic decline in the habitat. Of the 29 sites surveyed and based on their Area, Structure and functions and Future prospects, nine were as assessed as being in Favourable condition, 13 were as assessed as being in Unfavourable-inadequate condition and seven were as assessed as being in Unfavourable-bad condition. Two sites in particular, Shallee and Knockmahon Village, of those that are of high importance for rare bryophytes, are in poor condition and require conservation effort to maintain their importance. Two rare bryophyte species, Ditrichum plumbicola and Cephaloziella integerrima, were found to have declined at Calaminarian grassland sites, and may be in danger of extinction in Ireland. D. plumbicola was not refound at two sites where it previously grew, at one of which it grew in good quantity in 2008. It was refound at a third site, but in very small quantity and poor condition. C. integerrima was found at only one site, where it showed a marked decline due to pollution. Ditrichum cornubicum is also of concern, as it was only found in very small quantity at its only known site. A range of conservation measures are required to maintain and improve Calaminarian grassland habitat in Ireland, particularly at sites that are important for rare bryophytes. Clearance of scrub at a number of sites is required to maintain the habitat there, and minimising human impacts such as trampling and dumping would be beneficial across many sites. In order to improve the quality of habitat for rare bryophytes, removal of sources of pollution at one site is required, and removal of trees that are depositing leaf litter on Calaminarian grassland may be required at other sites. A beneficial measure across a number of sites would be to disturb and scrape back the surface of the mine spoil to expose more strongly metalliferous spoil on which metalophyte bryophytes can grow. Even with conservation measures in place, a continued decline of this habitat is likely to take place over time.

IWM Series Editors: Áine O Connor, Brian Nelson & David Tierney The NPWS Project Officer for this report was: Neil Lockhart, Neil.Lockhart@chg.gov.ie