RAMSAR CONVENTION ON WETLANDS OF INTERNATIONAL IMPORTANCE
CORSYDD MÔN A LLYN
ANGLESEY AND LLYN FENS
(Isle of Anglesey & Gwynedd)
Cors Goch, Cors Erddreiniog,
Cors Bodeilio, and Cors y Farl on the Isle of
Anglesey and Cors Edern and
Cors Geirch on the Llyn Peninsula (Gwynedd) comprise an internationally
important suite of base-rich fens, a rare wetland
habitat type which has undergone large scale decline in the British Isles.
While the base-rich fens of the Broadland district of East Anglia constitute their closest
biological counterpart on the British mainland, the
oceanic climate of north-west Wales results in the presence of a unique
assemblage of northern and southern floristic elements. The six component sites
share similar physical, chemical and vegetational
features but differ in their associated rarities of flora and fauna. The
composite site qualifies under Ramsar criterion 1d as an example of a type of wetland
which is rare and unusual in the biogeographic region and under
criterion 2b as it is of special value for maintaining the genetic and
ecological diversity of the region because of the quality and peculiarities of
its flora and fauna.
All six wetlands occupy former lake basins which have mostly infilled with marl and peat deposits, although in the cases of Cors Goch and Cors Erddreiniog
open water lakes persist. Calcareous springs from limestone aquifers (or
apparently in the case of Cors Geirch
and Cors Edern from shelly glacial drift) irrigate the fens and lead to a
distinctive vegetation of black bog rush - blunt flowered rush Schoenus n/gricans - Juncus subnodulosus hummocks
which is rich in plants such as narrow leaved marsh orchid Dactylorhiza traunsteineri, fly orchid Ophrys insectifera, common butterwort Pinguicula
vulgaris, long stalked yellow sedge Carex lepidocarpa and
the moss Scorpidium scorpioides.
In lower lying areas, swamp vegetation
dominated by stands of great fen sedge Cladium
mariscus, tufted sedge Carex
elata and slender
sedge Carex /as/oca/pa
is characteristic. These fens are notable as the best Welsh sites for stoneworts (large
freshwater algae which precipitate lime deposits and contribute to the
deposition of marl) such as dwarf stonewort Nitella tenuissima.
The fauna of these fens reflects the very
specialised nature of the habitat and includes rarities such as the marsh fritillary Eurodryas
aurina, southern damselfly Coenagrion
mercuriale, the soldierfly
Stratiomys chamaeleon, the fly Acrometopia
wahlbergi, medicinal leech Hirudo
medicinalis and Geyer's whorl snail Vertigo geyeri. These sites are also used by water voles Arvicola terrestris, otters
Lutra lutra, marsh
harriers Circus aeruginosus, hen harriers C. cyaneus, skylark Alauda
arvensis and lapwing Vanellus
vanellus.
These fens have a long history of low intensity human use, notably
extensive grazing, occasional burning and manual
peat cutting, which has maintained and even enhanced the biological interest.
In recent years many fens have deteriorated
either as a result of intensive drainage and eutrophication
(nutrient enrichment) or through the
abandonment of traditional management. Many of the remaining sites are owned and managed by conservation agencies, including Cors Erddreiniog National Nature
Reserve (NNR), Cors
Bodeilio NNR, Cors Goch NNR (the latter owned and managed by the North Wales
Wildlife Trust) and Cor Geirch
NNR.
Countryside Council for Wales
December 1997