Lead moss  (Ditrichum plumbicola)

This very rare moss can grow either as a dense mat of plants or a scattered group of individuals. It is yellowish-green in colour and its tiny glossy leaves are less than one millimetre in length.

Found only in Britain and Germany, lead moss’s UK range includes North and mid Wales, the Isle of Man, western Scotland and northern and southwestern England.

Lead moss is what is known as a pioneer species. This means it is one of the first species to colonise a new habitat or bare surface. As its name suggests, it is found around old lead mine spoil heaps, or on acid soils.

Although lead moss doesn't seem to obtain any benefit from growing on lead-rich soils and gravels, its tolerance of the high mineral content of a typical spoil heap probably gives it an advantage when competing for growing space. Many other plants cannot grow in such potentially toxic conditions. It also seems to prefer surfaces that have been subject to breaking up by the action of frost. These 'frost heaves' produce a knobbly surface, which appears to suit the moss. It is able to propagate itself by fragmentation, with new plants growing from small pieces of the 'mother' plant.

Many of the traditional lead mine sites where this moss grew have closed or been 'worked out' and, through the subsequent re-landscaping, the moss has disappeared. Remaining heaps are also being colonised by other plants as the sites become less toxic, and these threaten to shade out the lead moss. This moss, and others that grow on metal-rich soils are particularly threatened by the loss of old industrial land and mine workings. This is largely due to these sites being regarded as 'waste land', suitable only for re-development.

Lead moss is listed as a priority species in the UK Biodiversity Action Plan (UK BAP), and is included in English Nature's Species Recovery Programme. It is still unclear just how many sites in the UK have colonies of lead moss. Until this figure is known with greater accuracy, the true status of this species remains uncertain.

UK BAP Species Action Plan available on-line at:
http://www.ukbap.org.uk