Pollardstown fen is the largest remaining calcareous spring-fed fen in Ireland. Covering an area of 220 ha, it is recognised as an internationally important fen ecosystem with unique and endangered plant communities.
Undisturbed fens are rare in Ireland as their evolution into bogs is a natural progression. Moreover most Irish fens have been drained and developed for agriculture. This appeared to be the fate of Pollardstown when drainage work was undertaken during the 1960‘s to turn the fen into agricultural land.
However, in 1970, to mark European Conservation Year, two areas of intact fen were purchased by Bord na Móna. In 1981 Bord na Móna donated this conserved fenland to the National Parks and Wildlife Service. Other sections of the fen were purchased by the state and the fen was declared a National Nature Reserve in 1986.
The evolution of Pollardstown fen began after the last ice age, about 13,000 years ago, when retreating ice fields left behind a large hollow, filled with glacial meltwater and bounded by a glacial deposit of sand and gravel known as an esker. The lake was fed by calcium rich springs issuing from under the Curragh of Kildare, itself a great expanse of glacial gravel deposits. In time the mineral rich springs supported floating plant communities on the lake, while other plant species such as reed and sedge colonised the lake edge.
As these plants died they did not decompose fully, due to the lack of oxygen, and their remains collected on the lake bottom as fen peat. Over thousands of years the lake at Pollardstown became filled with the accumulation of peat to form a fen, and its surface now supports the distinctive fen vegetation to be found there today.
Pollardstown is best known internationally for its extensive areas of fen vegetation dominated by Black Bog Rush and Saw Sedge, a vegetation type almost unique to Ireland. Pollardstown also supports a number of rare and threatened plant species including the Fly Orchid, Pugsley‘s Marsh Orchid, Fen Bedstraw, Broad-leaved Bog Cotton, Tufted Sedge, Slender Sedge and Blunt Flowered Rush. Orchids to be found at Pollardstown include the Lesser Butterfly Orchid, Fragrant Orchid, Twayblade and the Marsh and Spotted Orchids. Insect-eating plants such as the Common Butterwort and Western Bladderwort are also present, while the Round-leaved Sundew can be seen growing on sphagnum moss in acidic parts of the fen.
The influence of man has left Pollardstown with a diversity of habitats including a central lake, reed swamps and forestry in addition to regenerating and intact fen. These habitats sustain a variety of animal species.
On a visit to Pollardstown in the summer you are likely to see Mute Swans, Herons, Little Grebes, Coot and Moorhen on the lake, while parties of Sand Martins swoop low over the open water hunting for insects. The fens, reeds and grasslands are home to Reed Buntings, Meadow Pipits and Skylarks. Some birds are more easily heard than seen: from the sedge and reed beds Water Rails call noisily and the drumming of Snipe can be heard; across the fen Sedge Warblers sing loudly in defence of their territories.
In winter these birds are joined by migrating wildfowl such as Pintail and Tufted Duck. A number of mammals live on the fen including the Otter, Hare and Pygmy Shrew, while the Common Frog and Smooth Newt are common amphibians. The fen supports many species of invertebrates such as dragonflies and damselflies, and butterflies include the Orange Tip, Green Veined White, Tortoiseshell, Speckled Wood and Common Blue.
Pollardstown Fen National Nature Reserve is located 3km west of Newbridge in Co. Kildare. A bird hide located in the southern section of the nature reserve is open to the public.