Page 14 - Conservation Impact Report 2016

Fen, reedbed and wet grassland

This broad category draws together different habitat Wet grassland in this context does not include hay-
types under the common requirement for the land cut lowland meadow; but does cover wet grasslands
to be wet; or to put it another way, hydrology is a key primarily managed for their wading bird and
factor for habitat quality and sustainability. invertebrate interest. The nesting sites of wading
birds including lapwing (Vanellus vanellus), redshank
Conservation Status (Tringa totanus) and curlew (Numenius arquata) are
wet grasslands with tussocky areas where fledging
Fens occur where groundwater is at or around the land chicks can shelter, and soft mud in which the adult
surface all year round, maintaining wet conditions. Of birds probe for their invertebrate food. Breeding by
the estimated 3400km2 of fen present in England in the main wader species has been steadily declining in
1637, only 10km2 remains today30. The water source for the Upper Thames catchment, 43% since 200532. Taller
a fen determines the plants and animals that make up swards, particularly with species such as reed sweet-
the wildlife present. All water ultimately comes from grass (Glyceria maxima) and greater tussock-sedge
rainfall; it is then fed into wetlands either from surface (Carex paniculata) are the habitat of Desmoulin’s whorl
flow or groundwater (soils or aquifers). snail (Vertigo moulinsiana) – a rare European protected
species which has suffered declines and for which the
The water in fens fed from aquifers will have dissolved outlook is classed as “bad” 33.
minerals. The resulting vegetation communities
contain many species adapted to both the water BBOWT manages 92 hectares of fen, reedbed
regime and the chemistry of the water. Base-rich fen and wet grassland: 99% of which is classified as
can be very floristically diverse, supporting a range of favourable or recovering.
specialist flora such as grass-of-Parnassus (Parnassia
palustris), black bog-rush (Schoenus nigricans) and
marsh helleborine (Epipactics palustris). The open water
found in the pools and streams on fen sites support
species such as common bladderwort (Utricularia
vulgaris) and a range of invertebrates including the
southern damselfly (Coenagrion mercurial) and the rare
calcareous fen specialist the clubbed general soldierfly
(Stratiomys chamaeleon).

Reedbeds are a type of fen, typically with very
high water levels and dominated by common reed
(Phragmites australis). Pure reedbeds often have very
low floral diversity, but do provide habitat for specialist
bird and invertebrate species such as bittern (Botaurus
stellaris), Cetti’s warbler (Cettia cetti), the scarlet tiger-
moth (Callimorpha dominula). Historically reedbeds
were widely distributed and covered large areas (e.g.
the Norfolk and Lincolnshire fenlands), but agricultural
management has reduced the current extent to around
6,500ha, with only around 15 sites being larger than
40ha31. The majority of sites are coastal, and sizeable
inland reedbeds in southern England are rare.

Fen at a nature reserve

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