Atlantic lejeunea  (Lejeunea mandonii)

The principle threats to this species are the deterioration of water quality throughout its range, through agricultural run-off and other forms of pollution, and the colonisation of much of its former habitat by encroaching rhododendron and scrub. It is intolerant of excessive shade. Rhododendron ponticum is an invasive species, which has been threatening much of our native upland habitat over the last few decades. While many people find it an attractive sight, especially when the shrub is in flower, rhododendron has the potential to devastate any habitat it colonises. The plant can spread at a rapid rate and its canopy has the ability to reach areas some considerable distance from the roots. It is also toxic to many grazing animals and insects, so it is difficult to control in any way except by laborious cutting and clearance. As well as producing dense shade, which prevents the germination of anything beneath the plant, rhododendron also grows in association with a particular fungus around its roots. This fungus effectively poisons the ground for years, even after the rhododendron itself has been removed, and any plant attempting to colonise the site will be killed. Except, of course, more rhododendron.

Atlantic lejeunea is listed in the UK Biodiversity Action Plans and included in English Nature's Species Recovery Programme. Plantlife, who are the lead organisation for this liverwort, hope to be able to re-introduce it to suitable former sites during the next few years. As it is also a globally scarce species, information on management and propagation of the liverwort by the Royal Botanic Gardens, Kew, will be made available to the World Conservation Monitoring Centre.