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 RaheenmoreRaheenmore is a classic example of an Irish Midland raised bog with a characteristic dome shape and typical raised bog vegetation.
It was purchased by Bord na Móna to mark European Conservation Year in 1970
and was subsequently donated to the National Parks and Wildlife Service. It is
an internationally important raised bog and is now a 162 ha National Nature
Reserve.
The origins of Raheenmore bog can be traced to the last Ice Age which ended about 13,000 years ago, when the scouring action of the retreating ice field formed a deep basin surrounded by low hills of glacial drift. This basin was subsequently filled with glacial meltwater to create a lake where Raheenmore bog now lies.
As the climate became warmer, vegetation began to colonise the post-glacial
landscape. At Raheenmore, waterlilies became established on the open water
while reedbeds and other aquatic plantlife encroached the lakeshore. As plants
died back and their remains sank to the lake bottom, they only partially
decayed because there was insufficient oxygen available for full decomposition
to take place. This accumulation of plant debris on the shellmarl of the lake
floor formed a layer of peat
As the lake became choked with the encroaching reedswamp and decaying vegetation, marsh plants began to invade the swampy ground. These communities of marsh plants, growing on the peat formed from partially decayed vegetation and fed from alkaline groundwater, are known as fens. In places this fen vegetation was invaded by birch woods and as it decayed a layer of peat known as woody fen peat was produced. The layer of woody fen peat grew until the roots of the fen vegetation began to lose contact with the mineral rich groundwater. Sphagnum mosses can grow in conditions where the only source of nutrients is from rainwater and these plants now began to flourish. The invasion of sphagnum mosses was accelerated by the change to a much wetter climate about 5000 B.C. The alkaline conditions of the fen gave way to the acidic conditions of the bog as sphagnum mosses and bog cotton thrived. Sphagnum mosses have the capacity to collect and retain enormous quantities of rainwater. Their leaves have an open cell structure and can hold up to 20 times their weight in water. As the mosses grew they drew the water table upwards, building a deep saturated mass of partially decayed plant remains and eventually growing to rise above the surrounding countryside. The peat deposits in Raheenmore are exceptionally deep, up to 15m in places.
From a distance Raheenmore may appear to be an open uniform landscape of undistinguished low-growing vegetation. However to properly appreciate the uniqueness of a raised bog the visitor must look more closely, at the varied plant life which has adapted to the peculiar acid peatland environment. The sphagnum mosses which make up the top layers of the bog grow in hummocks and hollows on the bog surface, creating spongy carpets of bright green and red. The hummocks support a range of plant species particularly those preferring drier conditions. Cross-leaved Heath, Ling Heather, and Bog Rosemary are all typical plants which can be found growing in these situations. Lichens are characteristic of dry hummocks and a variety of species occur, the most common being the coral-like Reindeer Lichen. In the wetter hollows, Bog Asphodel and Bog Cotton are common, while White-beaked Sedge and Bog Bean are found by permanent pools. The Cranberry can also be found in the wetter parts of Raheenmore bog. Plants which grow on the surface of raised bogs depend on rainwater for the minerals essential for plant growth. In response to this difficult environment, a number of plant species have developed ways of trapping and digesting insects to supplement their mineral intake.
The Round-leaved Sundew is a tiny carnivorous plant which can be found growing
on the edges of
Raheenmore bog is home to a number of unusual and scarce animal species adapted to the unique bog environment. The most striking bird is the Curlew whose distinctive bubbling call can be heard drifting across the heather in the early summer. This is a large wading bird with a long curved bill designed for probing the mud for food. It nests on the bog at Raheenmore and winters on coastal estuaries. Other wading birds commonly found at Raheenmore are Snipe on the high bog and Lapwing on the cutaway. The song of the Skylark is a classic summer sound at Raheenmore, as birds sing across the bog in defense of their territories. Meadow Pipits are common, while Willow Warblers sing from the birch woods which fringe the bog. The Red Grouse, which is historically associated with boglands, is now a scarce resident of raised bogs but has been seen at Raheenmore. The Irish Hare is the most conspicuous of the larger mammals present and is often encountered by a visitor to the bog. Butterflies, moths, dragonflies and damselflies are the most colourful and easily recognisable insects to be found on Raheenmore bog. The Large Heath, a butterfly which is largely confined to bogs, is found at Raheenmore. while dragonflies such as the Four spotted Chaser can be seen hunting across bog pools. Heather is the food source for the caterpillar of Ireland‘s only silkmoth, the Emperor Moth. In recent years, hydrological and botanical investigations at Raheenmore revealed that the bog was drying out and restoration work became necessary. A rehabilitation programme was developed by Dutch engineers experienced in the conservation of peatlands. Bord na Móna‘s own technical experience and knowledge of working on peatlands was then applied in constructing peat dams and inserting plastic retaining sheeting in the south-east corner of the bog. These dams prevent bog subsidence which causes water loss and drying out of the bog surface. The effectiveness of the restoration work is being monitored so that the experience gained at Raheenmore can be applied elsewhere in bog conservation projects.
Raheenmore National Nature Reserve is not open to the public.
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known
as reedswamp peat.
Looking
across Raheenmore today, the tops of fringing birch trees just visible above
the bog horizon or a solitary chimney rising from a hidden farmhouse reveal
the bog‘s characteristic dome shape, swelling above the surrounding
countryside in a manner which gives these bogs their distinctive name of
raised bogs.
small
pools in Raheenmore. The spoon-like leaves of the sundew are edged with long
sticky tentacles which trap insects in the manner of fly paper. Digestive
enzymes, which the sundew secretes, enable it to dissolve and absorb growth
promoting nutrients from its prey, including nitrogen, phosphorous and
potassium.
