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Pollardstown Fen, Co. Kildare Visitor Guide

INTRODUCTION

Pollardstown Fen is situated on the Northern margin of the Curragh, approximately 3km west north west of Newbridge, Co. Kildare (grid ref. N 765160). The area of the fen is 235 hectares, 60% of which is state owned.

A fen is an area of alkaline peatland which obtains its nutrients from calcium-rich spring water. Most fens develop further into raised bogs. Raised bogs contain acid peat and their only source of nutrients is rainfall.

Pollardstown Fen is of international importance as this type of system is now rare in Ireland and Western Europe. In addition, it contains a number of rare vegetation types and invertebrates, along with an uninterrupted pollen record of the changes in the composition of its vegetation going back to the last ice age (Figure 1).

Figure 1: Shows an aerial photograph of Pollardstown Fen. In 1963 a culvert was opened under the feeder canal to drain the fen. This culvert was blocked in 1983 and allowed the area to flood in turn forming the shallow lake that you see in the photograph.

FORMATION OF POLLARDSTOWN FEN

About 12,000 years ago, at the end of the last ice age, this area was covered by a large shallow lake. This lake formed when the ice melted because drainage was prevented by the presence of eskers, ridges of sand and gravel left by melting ice. The lake was fed by calcium-rich springs originating under the Curragh. Calcium was precipitated out of the mineral-rich water and deposited as a layer of marl on the bottom of the lake.

In time plants began to grow around the edges of the lake and float on the surface. These plants did not rot completely when they died due to the lack of oxygen and their remains accumulated on the edges and bottom of the lake as fen peat. Marl was deposited whenever open areas of water existed, giving rise to alternating layers of marl and fen peat.

After several thousand years the original lake became completely filled with fen peat and the area was covered with swamp and fen vegetation, as you see today. During the last 12,000 years, over 6 metres of marl and fen peat have been formed. This is unusual as most fens tend to either dry out and be invaded by trees, or grow above the influence of the calcium-rich water and become raised bogs. The long continued growth of peat on Pollardstown Fen is probably due to the presence of the calcium rich springs situated high on the surrounding slopes.

Figure 2: Ordanance Survey map of Pollardstown Fen. The yellow areas are owned by the state, while the blue areas are privately owned by memebers of the publc. The National Parks and Wildlife Service began purchsing parts of the fen in 1981 with the aim of blocking culverts opened for drainage . In 1983 these culverts were blocked allowing the area to flood once again.

THE HISTORY OF POLLARDSTOWN FEN

Man has held considerable influence on the fen during its past history. The earliest evidence of man is at the edge of the fen on the esker ridge, where prehistoric burials were unearthed. Unfortunately, however, these were destroyed by the mining of sand and gravel.

Streams on the fen were used by man to power a number of mills, perhaps as early as pre-Norman times. More recently, in the 1790"s, the Grand Canal Company diverted the streams on the fen into 2 converging canal feeders cut into the peat. The two join to form the Milltown feeder for the Grand Canal, which is the only source of water for the canal at its summit level. The original size of the fen has been reduced by turf cutting over hundreds of years. At one time the fen was almost three times its present size. The last period of extensive cutting on the fen was during World War 2 on the area now covered with forestry. It was planted with trees by the Forest and Wildlife Service (now Forest Service) in 1963. The trees did not grow well, however, due to the presence of a layer of marl which was close to the surface because the peat above it had been cut away. This area is now owned National Parks and Wildlife.

In the 1960's drainage started on the part of the fen between the two canal feeders, to convert it into agricultural land. Ditches and drains were dug and in 1964 a culvert was dug under the canal feeder which drained the area effectively. In 1981 National Parks and Wildlife began purchasing this part of the fen. In 1983 the culvert was blocked and part of the area flooded to form the shallow lake which you see today. This has allowed the fen vegetation to regenerate (Figure 2).

The fen was declared a National Nature Reserve in 1986. It is also a Special Area of Conservation No. 396 recognized by the European Union.

The hill you can see on the northern horizon is known as the Hill of Allen. Mention of the hill can be found in early Irish literature as the legendary hero Fionn mac Cumhaill used as a camp. More recently, in1859, Sir Gerald Aylmer of Donadea built the tower you can see on top of the hill.

FAUNA OF POLLARDSTOWN FEN

Pollardstown Fen contains a wide diversity of habitats such as the lake and canal feeders. Reed and Saw Sedge swamps and damp grasslands. These support a variety of different animals.

BIRDS: From the bird hide you can see the lake, and some of the rest of the fen. Birds you can see on the lake include Black Headed Gulls, Mute Swan, Mallard, Teal, Coot, Moorhen, Water Rail, and Little Grebe. During the winter the number of birds on the lake increases due to the arrival of winter migrants such as Pintail and Tufted Duck.

Throughout the year you can see birds such as Reed Buntings and Wrens amongst the Reeds and Saw Sedge. Summer visitors to the habitat include the Sedge Warbler and Grasshopper Warbler. In addition the rare visitor to Ireland the Savi's Warbler has been seen on the fen.
Birds you can see in the damp grasslands include Snipe, Meadow Pipit, while overhead Sparrowhawks and Kestrels hunt.

MAMMALS: Mammals tend to hide from humans and are seldom seen on the fen although they leave evidence of their presence such as tracks and droppings. Mammals living on the fen include Otters, which are becoming rare in Europe and Hares and Pygmy Shrews. Foxes and Badgers use the fen as a hunting ground but do not live there as the ground is too wet for their dens.

AMPHIBIANS: Because the ground is wet it is the ideal habitat for the Common Frog and the smooth Newt which lay their eggs in water. Booth these animals can be seen all over the fen.

INVERTEBRATES: The fen has a large number of invertebrates {animals without backbones} both in the water and on the land. Present in the water are Bloodworms, Caddisfly larvae, Water Beetles and Water Mites to name but a few. On the surface of the water you can see Pond Skaters and Whirligig Beetles. On the ground you can see Beetles, Caterpillars and Snails, while in the air you can see Butterflies, Moths, Dragonflies, and Damselflies.

Butterflies are probably the largest most colourful invertebrates to be seen on the fen, and those you can see include the Orange Tip, Green Veined White, Speckled Wood, and Common Blue, Moths present on the fen include the Emperor Moth, the Fox Moth and the Cinnabar and Six Spot Burnet Moths.
A number of rare invertebrates have been found on fen such as rare Caddisfly (Leptocerus tineiformis) a rare fly (Platycheirus amplus) and a rare semi-aquatic snail (Vertigo geyeri

FLORA AND VEGETATION OF POLLARDSTOWN FEN

The vegetation of Pollardstown Fen was first described in some detail by two botanists, Braun-Blanquet and Tüxen, who visited the fen in 1949 as part of the 9th International Phytogeographical Excursion.

There are many different types of vegetation including that consisting of Black Bog Rush (Schoenus nigricans) Meadow Thistle (Cirsium dissectum) and Saw Sedge (Cladium mariscus) which Braun Blanquet and Tüxen called the Schoenus nigricans-Cirsium dissectum association. They considered this vegetation type to be unique to Ireland although it has recently been found in Western France.

The lake and old drainage ditches consist of swamp vegetation types containing mostly Reeds and aquatic plants such as Water Mint, Water Horsetail, Lesser Duckweed and Whorled Water Milfoil. The area also consists of areas of damp grassland containing Purple Moor Grass and vegetation types associated with old peat diggings. The vegetation of the fen margin is extremely varied due to the presence of springs and the influence of the surrounding mineral soil. The marginal types include wet grassland on mineral soils and Rush and Sedge dominated vegetation types on the wetter peats.
As well as being important for vegetation types, the fen is also important for the rare and threatened plants it contains the Fly Orchid, Pugsley's March Orchid, Fen Bedstraw, Broad -Leaved Bog Cotton, Tufted Sedge, Slender Sedge and Blunt Flowered Rush.

Many orchids can be seen flowering amongst the vegetation throughout the summer such as the Lesser Butterfly Orchid, Fragrant Orchid, Twayblade and the Marsh and Spotted Orchids.

There are a number of insect-eating plants on the fen such as Common Butterwort and Western Bladderwort which can be found in the lake and ditches, and the Round-Leaved Sundew.

Round-Leaved Sundew is a plant normally found on acid peat and on Pollardstown Fen it is found growing on Sphagnum moss. The presence of Sphagnum moss along with plants such as Ling Heather and Cross-Leaved Heath indicate that parts of the fen are acidic in nature. With time the natural progression would e for the whole fen to turn into a raised bog, with the formation of acid peat.

Pollardstown Fen has a rich diversity of mosses in its ground layer. This group which includes up to 20 species are known as the brown mosses and include the rare arctic-alpine moss (Homalothecium nitens).

NATIONAL PARKS AND WILDLIFE

National Parks and Wildlife manages Pollardstown Fen, ensuring that activities by man do not damage either the fen, or the numerous springs surrounding the fen, which are its source of water. Work on the fen is ongoing and it is hoped to remove all the forestry from the fen in the near future. Fen plants will then be allowed to regenerate in the area.

BOG OF ALLEN NATURE CENTRE

If you wish to find out more about peatlands you can visit the Bog of Allen Nature Centre, which is being developed by the Irish Peatland Conservation Council at Lullymore, approximately 3 miles from Allenwood in Co. Kildare. At this centre you will be able to get information on the development of peatlands and their flora and fauna and there is a special exhibition about Pollardstown Fen on permanent display. In addition, historical artifacts found preserved in the bog will be displayed.

VISITING POLLARDSTOWN FEN

Pollardstown Fen is approximately 3km WNW of Newbridge, Co. Kildare. Take the turn for Milltown opposite the Post Office in Newbridge. Turn left in Milltown. The area of intact fen can be entered by walking along the left hand side of the Milltown feeder canal bank opposite the Hangman's Arch pub. The area of regenerating fen can be reached by travelling past the Hangman's Arch pub, along the road for Kildare. After Father Moore's well take the first left turn. Continue along this road for 2 km. The entrance is through the gateway on the left hand side at the foot of the hill beside the gravel pit. An information board and bird hide are present on this side of the fen.

Due to the presence of deep overgrown drains it is not advisable to go outside the fence unless accompanied by someone who knows the area, such as the local Wildlife Ranger. Visitors who go beyond the bird hide are advised to wear Wellington boots and protective clothing. The Office of Public Works cannot accept any liability to any persons injured while visiting the fen. Removal of living or non-living things from the fen is strictly prohibited (Figure 3).

FURTHER READING ON FENS

Anonymous (1976) Wetlands Discovered. Forest and Wildlife Service, Dublin.
Cross, J. R. (1989) Peatlands, Wastelands or Heritage? An introduction to Bogs and Fens. Wildlife
Service, Dublin.
Crushell, P. (2001) Fens. Factsheet published by the ENFO Centre, Dublin.
Doyle, G. J. (1984) Pollardstown Fen. In: Nature Conservation in Ireland: Progress and Problems. Ed. Jeffrey, D. W. Royal Irish Academy 1984. pp 37-48.
Goodhue, D. (1980) Irish Bogs and Fens. No. 63 of the Irish Environmental Library Series, Folens,
Dublin.
O'Connell, C. (1987) The IPCC Guide to Irish Peatlands. Irish Peatland Conservation Council, Kildare.

ADDRESSSES FOR CORRESPONDANCE

National Parks and Wildlife, Ely Place, Dublin 2.
Bog of Allen Nature Centre, Lullymore, Rathangan, Co. Kildare. Tel. (045) 860133.

ACKNOWLEDGEMENTS

This brochure was prepared as part of a FAS, C.Y.T.P. training programme sponsored by Teagasc. Text by FAS, trainees, Linda Patton and National Parks and Wildlife.

Figure 3: An adult education course run by the IPCC at Pollardstown Fen in 2003. If you are planning to visit Pollardstown Fen be sure to remain inside the fenced area at all times. If you do plan to go outside the fenced area it is advisable to go with someone who knows the area such as the local Wildlfe Ranger. Photo: © Catherine O'Connell