Nowell's limestone moss  (Zygodon gracilis)

With a species confined to just one relatively small area, the threats to its survival are great. In the case of this moss, the destruction or re-building of dry stone walls poses a serious danger unless this work is carried out sympathetically. The moss also seems to be threatened by the toxins associated with the zinc netting sometimes placed on top of walls to increase their stock-proofing.

Nowell’s limestone moss is listed as a priority species in the UK Biodiversity Action Plans (UK BAP), and is included in English Nature's Species Recovery Programme (SRP). Until the discovery of the fruiting moss in 2002, plans for conserving the species included establishing an ex-situ colony, in order to ensure the possibility of propagating specimens for a future re-introduction programme. However, in spite of this discovery, and because it is such an endangered species, ex-situ colonies will be maintained, and trial re-introductions will go ahead. It might even prove possible to carry out some careful 'match-making' on the plants in the wild. Fred Rumsey and his colleagues hope to aid the mosses' chances of reproducing by placing pieces of male and female moss next to one-another. If it works, it will avoid the need to re-create an artificial habitat in the lab on which to propagate the moss prior to cross-fertilisation.