In selecting the series of key mire sites,
an attempt has been made to include
representative examples of the range of variation within each of the six main
categories of peatland, balancing the numbers and areas chosen against the
frequency of occurrence and general extent of each of the six types. In addition,
special attention has been given to representation of the following features:
1. The marked differences in flora and
fauna which art-associated with change in
geographical position from south to north and east to west, in each main category
of peatland. Efforts have been made to include good populations of all the more
characteristic or exclusive mire species.
2. The wide range of nutrient status of
water and peat (from oligotrophic to
eutrophic) and associated biological differences found in the topogenous mires
(valley, basin, open water transition-flood plain, and soligenous mire).
3. The marked variations in surface structure
of blanket mires and, to a lesser
degree, raised mires. Blanket mire is a type of peatland especially associated with
the oceanic British climate, and is thus of considerable international importance. It
is by far the most extensive major type of peatland now remaining in Britain but the
best (i.e. least disturbed) examples are all in Scotland or the extreme north of
England, so that there is bias towards selection of sites in these districts. The
range of altitudinal variation in this class of mire has also been represented.
4. Undisturbed Sphagneta in various
types of mire. Disturbance here includes not
only factors which cause drying out and reduction of Sphagnum cover, but also
chemical changes produced by inflow of fertilisers and sewage.
5. The important breeding bird communities
especially associated with the larger
open water transition and flood-plain mires, where not covered by i above.
6. Mires known to be important for their
invertebrate fauna, where not covered by i
above.
7. The range of stratigraphic sequences
characteristic of British mires, especially
those extending back to the Late Weichselian Period.
