Peat moss
Sphagnum is an unassuming plant; individual specimens are only a few inches tall and consist of a single central stem with short side branches bearing tiny, closely-packed leaves, anchored by shallow roots. In colonies, thousands of plants form a low blanket, covering large areas of land. However, Sphagnum's impact is more dramatic than its appearance; it is crucial in maintaining peat bog ecosystems and played an important role in World War One (WWI).
It thrives in waterlogged, acidic areas where few other plants can survive. In these conditions, dead plant material does not fully decay, but is compressed over thousands of year to form peat. Sphagnum contributes to this environment by secreting chemicals which further acidify its surroundings, and is itself highly resistant to decay. As the 'habitat architect' it is responsible for the ecosystem of the peat bog, ranging from the tens of thousands of microscopic creatures which live in the moss itself, to larger vertebrates. Many of these species live only in peat bogs.
Another achievement of Sphagnum was its role in medical treatment in WWI. Dried moss can take in up to twenty times its own weight in liquid, and although the idea of moss in hospitals may sound odd today, its powers of absorption made it ideal for wound dressing, being more effective than cotton and easier to obtain. It also has antiseptic qualities, which were crucial in WW1 when soldiers lived in unsanitary conditions and wounds often became infected. The moss was harvested in Scotland, England, Ireland and Canada. While Sphagnum had been used in medicine for several centuries, WW1 saw it employed on an industrial scale for the first time; tens of millions of dressings were produced. The Royal Botanic Garden Edinburgh assisted in determining the best species of moss to use and how to prepare it.
Sphagnum has also been used for bedding, lamp wicks, in babies' nappies, and as tinder. Its history of use by humans, as well as the range of organisms which depend on the peat bog habitat, demonstrate how even a tiny moss can be vital to the species that live alongside it.
However, huge areas of bog have been lost through human activity, including the harvesting of peat, and habitat destruction through pollution and agriculture. Efforts are now being made to reduce the amount of peat used in horticulture, and to give protected status to remaining peat bogs.
Further reading
Ayres P 2013. Wound dressing in World War I - the kindly Sphagnum moss. Field Bryology 110: 27-34.
Clymo RS and Hayward PM 1982 The ecology of Sphagnum. In Smith AJE (ed) The ecology of bryophytes. Chapman and Hall. Pp. 229-289.
Rochefort L 2000. Sphagnum - a keystone genus in habitat restoration. The Bryologist 103: 503-508.
Ruth Calder