Life Conference: Cors Erddreiniog

Cors Erddreiniog is the largest of the Anglesey fens covering 289ha thus making access to the site quite difficult unless you can speak the secret language of 'farmer'. Luckily, the project had a few translators on hand.

The large site is lime rich and made up of a mixture of habitats, similar to Cors Goch it was formed by the terrestrialisation of Llyn yr Wyth - a glacial lake. The centre of the site is comprised of calcareous fen with areas of alkaline fen and both wet and dry heathland around the edges. Being such a rare type of wetland the site is protected by RAMSAR and is recognised as a SSSI and also a SAC.

Redirected spring water

For many years the site was used for agriculture and many ditches had been dug to drain the land, this along with the use of fertilizers had drastically reduced biodiversity at the site. Management of the site has improved the quality of the fen, by filling in drainage ditches and the with use of a piston bully, the site is now know as "Jewel in the crown of Anglesey fens".

The piston bully was used to remove vast amounts of "improved soils". These are soils which have been heavily fertilized and are not suitable for peat producing species to colonise. The LIFE project removed the soil and exposed the white marl that lay beneath the top layers, by diverting the spring waters hydrological pathways to what they would have naturally been, a new lease of life was given to the site. Seeing natural colonisation of many wetland loving species.

Constructed wetland in the foreground
natural wetland in background

The water to the fen is fed by limestone 3 springs and before it reaches its destination some of the spring water passes through a specifically constructed wetland. The constructed wetland is used as a treatment area to denitrify the spring water utilising denitrifying bacteria. The water that enters the wetland has been contaminated with N from the fertilizers of the farms surrounding the site. The constructed wetland was colonised naturally with species such as Stonewort. Some spring water is also passed through a mixing chamber which also removes excess N. The denitrifyed water can then spread over travel down to the site, specific fen species such as M15 and M19 have a higher chance of establishing in the areas where N has been removed from the water. The communities of these species developed over 5 years which is surprisingly fast compared to other less well managed sites.

To keep the fen in prime condition grazing is carried out by some dairy cattle of  the local farmers. However the dairy cattle cannot be kept here for a long period of time because of the poor nutrient content of the grazing. The LIFE project introduced Konic and Welsh Mountain Ponies onto the site during the times when cattle grazing is not suitable. Grazing is a key part in the management of the site, it prevents build-up of a thick thatch of vegetation which prevents light penetrating through to establishing plant species. In more sensitive parts of the site local contractors are hired to strim cut the vegetation.

Wildlife
There is a rich variety of wildlife found at Cors Erddreiniog. I will list some below..

• Great fen sedge
• Blunt-flowered rush
• Black bog rush
• Columbine
• Grass-of-Parnassus
• Sphagnum moss
• Cross leaved heath
• Marsh gentian

Bog stars also known as Grass of Parnassus

The site is special to contain many species of orchid that cannot be found anywhere else in Britain other than a few sites on Anglesey and the Llyn Peninsula. These include

• Northern marsh orchid
• Fen orchid
• Marsh helleborine
• Fly orchid

Insect life is rife at the reserve, the marsh fritillary, one of Britains most threatened butterflies can be found here along with species of dragonfly and damselfly, including the rare southern damselfly. With insects usually comes birds, the fen attracts a variety of bird life with winter bringing hunting hen harriers and lapwings to the site and with the arrival of summer sees birds such as the willow tit and grass-hopper warblers arriving at the reserve. There are also many other animals at the site, so eyes should be kept peeled for toads, adders, otters, brown hare and water voles.