Cornish path moss (Ditrichum cornubicum)

SizePlant size: 1 - 5 mm

Cornish path moss is classifed as Endangered (EN) on the IUCN Red List (1).

The extremely rare Cornish path moss (Ditrichum cornubicum) was first discovered in 1963 and only identified as a distinct species in 1976. It appears as dull-green patches or as scattered shoots on compacted loamy soil, or soils associated with copper contaminated mine spoil. Only male plants have been found.

Cornish path moss has, so far, only been recorded in the British Isles, originally, from three sites. It is now restricted to just two. It is endemic to the UK.

This plant is one of the few species which are tolerant of copper minerals in the concentrations found at old copper mines. Cornish path moss is termed an 'early colonist', meaning it is one of the first plants to appear on bare ground, but it can be shaded out by taller plants when they, in turn, become established.

Mosses, hornworts and liverworts form a group of plants called bryophytes. Bryophytes lack many of the more complex structures of the higher plants, such as a vascular system, and flowers. They do not have roots, instead they have structures called ‘rhizoids’ which absorb water and anchor the plant to the substrate. All bryophytes have an interesting life cycle consisting of two main parts, called the gametophyte and sporophyte generations. Plants that are in the gametophyte stage can reproduce sexually. Male organs (antheridia) produce male sex cells or gametes called antherozoids, which actually move to the female sex organs (archegonia) through water droplets. Fertilisation occurs and a plant develops called a ‘sporophyte’, which remains attached to the plant. The sporophyte releases spores from within a capsule; the spores disperse and develop into a new gametophyte stage plant.

Although the reasons for the decline of this species are not fully understood, it is believed that accidental loss from trampling and vehicle movements, and enrichment of the ground by sheep dung has resulted in the Cornish path moss's decrease at one of its sites. Its disappearance from a site in West Cornwall was due to the surfacing of a lay-by.

This species' rarity and the precarious state of its habitat meant that it was included in the original UK Biodiversity Action Plans for species, and it is also listed in English Nature's Species Recovery Programme (SRP). Initial work on conserving the Cornish path moss concentrated on maintaining the plant's only known site, and in 1996 it was designated a Site of Special Scientific Interest (SSSI). With the moss's sites now under protection, a management plan was produced and an ex-situ conservation programme was begun to propagate the moss, and allow for possible introduction to other suitable sites. This was part of the bryophyte conservation programme, run by the Royal Botanic Gardens, Kew, and should provide an insurance safeguard against the extinction of this species in the wild. However, the most important issue is to ensure that the natural populations remain viable, and the major conservation efforts are being directed towards this goal.

Part of the plan for conserving the Cornish path moss will involve the sharing of knowledge gained in the study of this plant. All over the globe, species like this rare moss are threatened with extinction. Knowledge gained by the research into why a plant or animal is rare or becomes endangered, is of immense importance in learning how to manage our planet in a more sustainable way. The Cornish path moss project is just a small part of a global programme to maintain and enhance the Biodiversity of planet Earth.

Find out more on the bryophyte conservation programme:

Information supplied by English Nature.

  1. IUCN Red List (April, 2011)