Fen Management Handbook - Scottish Natural Heritage

2.1 Diversity and conservation significance
Two of the major factors which determine the botanical composition of fens are
fertility and base-richness/pH (see Section 4: Understanding Fen Nutrients and
Wheeler and Proctor, 2000). To some extent these directly affect fauna as well,
particularly invertebrates, but their major effect is indirect in that faunal composition
of fens is determined largely by vegetation structure and water levels.
In general, the wider the range of habitats, the higher the diversity of associated
vertebrate and invertebrate species, although less diverse fens can also be very
important for uncommon vegetation communities and specialised plants and
animals. Reedbeds, which are a type of fen, are a good example of this. They can
be botanically poor, but are one of our most important bird habitats, supporting
highly specialised species such as bittern (Botaurus stellaris) and marsh harrier
(Circus aeruginosus).
Elsewhere, specific and often very restricted areas of a particular fen type may
support other specialised species such as the Irish damselfly (Coenagrion
lunulatum), a native of northern Europe, rarely found outside northern Finland. The
Irish population is thought to be one of the largest in western Europe, highlighting
the fact that even fens which are not particularly diverse in terms of the range of
species they support, can be of very high conservation importance.
Irish damselfly is
restricted to open pools
and small lakes within
acid fens frequently
associated with cutover
bog (G. Campbell).
Aerial view of Bemersyde
Moss in the Scottish
Borders
an oasis for wildlife in
an intensively managed
agricultural landscape
(P& A MacDonald/SNH).
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