Knothole moss  (Zygodon forsteri)

Whilst never common, this moss is threatened by the felling of its host trees, possibly through safety considerations. The famous 'hurricane' of October 1987 that tore through southern England, also felled several host trees in Epping Forest. Another long-term issue is creating replacement pollarded trees for the future. A continuity of suitable trees is essential for the moss to survive at any one particular locality. Another, rather ironic factor, is the increase in competing species of moss which have benefited from the reduction of acid rainfall. These other mosses are suspected of crowding out the knothole moss. Moss collecting is another possible threat as a small colony of knothole moss could be removed completely by an irresponsible collector.

Knothole moss is listed in the UK Biodiversity Action Plans and also included in English Nature's Species Recovery Programme. As it is rare it is vitally important to conserve the remaining colonies of the moss and, where possible, increase the populations.The sites where the moss is known to grow are now all within Sites of Special Scientific Importance (SSSIs). A management plan exists for conserving the species and is available to all managers of these sites. Surveys are also taking place to establish the true extent of this species and whether colonies can be grown in culture for potential re-introduction programmes.