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Blanket Bogs

On the 15th June 1919, the first non-stop powered flight across the Atlantic ended, nose down in Derrygimla Bog near Clifden in Co. Galway. The cool, moist westerlies that helped Alcock and Brown to achieve this historic crossing and earn their place in the Guinness Book of Records, do more than carry intrepid aviators to the western shores of Europe - they play a major role in the development of our world famous blanket bogs.

After the westerlies have completed their 6,500km journey from the eastern seaboard of America, they carry enough moisture to produce rain on 2 out of 3 days in the West of Ireland. The Gulf Stream also has a role in moderating our climate, ensuring cool temperatures throughout the year. This climate, coupled with a geology of hard, acidic rocks, produces landscapes which are swamped by a type of peatland known as blanket bog.

Types of Blanket Bog
Blanket bog is so called because its development is mostly independent of basins or topographical features where water collects; it simply covers the landscape like a blanket. Peat develops due to a continuous supply of water from rainfall, maintaining waterlogged conditions on the ground. Blanket bogs are ombrotrophic or rain fed, and as a result their pH lies between 3.5 and 4.2. In Ireland the distribution of blanket bogs is confined to an area west of the 1,200mm isohyet, and all upland areas where precipitation is high and evaporation is low (see Figure 1). There are two types of blanket bog in Ireland.

Atlantic Blanket Bogs are found in low-lying coastal plains and valleys in mountainous areas of western counties, below 200m O.D. They are particularly well developed in counties Donegal, Mayo, Galway, Kerry, Clare and Sligo

Mountain Blanket Bogs occur on relatively flat terrain in the higher Irish mountains above 200m O.D. and are more widely distributed than Atlantic blanket bog.

Atlantic blanket bogs and mountain blanket bogs are the most extensive of the Irish peatland types and originally covered an area of 774,360ha.

Formation of Blanket Bogs
Blanket bog formation in the mountains and lowlands of the west of Ireland started at the end of the last glaciation, 10,000 years ago. Initially peat formation was confined to shallow lakes and wet hollows. In these situations a process of infilling or terrestrialisation took place in a sequence from open water to alkaline fen and acid blanket peat. Later, the blanket bog spread out from these basins to cover huge areas of land. While some spread may have taken place as early as 7,000 years ago, many areas were not engulfed until 4,000 years ago when the climate became wetter (see Figure 3). Heavy rainfall caused minerals such as iron to be washed out or leached from the surface layers of the thin soil, in a process known as paludification. These were deposited lower down in the soil profile where they formed an impermeable layer known as an iron pan (see Figure 2). As water cannot move down through such a layer, the soil surface became waterlogged. Under these conditions the accumulation and spread of peat was made possible. The accumulation process is slow, perhaps no more than 1mm every year, but the process has been going on for millennia. The peat forms a blanket over the landscape of varying thickness from 2 to 7m, with an average depth of 3.5m.

Today in the west of Ireland the blanket bog rests directly on the stumps of Scot's Pine trees that were once part of extensive woodlands in the area and also covers large areas of land that were cultivated by farmers, 5,000 years ago.

Blanket Bog Habitats
From the air blanket bog surfaces are highly patterned because of the presence of a variety of habitats in the peatland including flat and sloped areas, flushed fens, swallow holes, pools, lakes, hummocks and ridges. These varied habitats contribute to the wonderful diversity of species of plant, animal and bird found in blanket bogs.

Vegetation of Blanket Bogs
The vegetation of Atlantic and mountain blanket bogs are different from one another. Atlantic blanket bog vegetation has a characteristic grassy appearance that is not present on other peatland types. This is mainly due to the dominance of grasses and sedges. Mountain blanket bogs have a shrubby appearance due to the dominance of ericoid shrubs.

Grazing and burning have been features of Atlantic blanket bogs since the Stone Age, 5,000 years ago and have contributed to the formation of the vegetation that currently characterises the bog surface. In the waterlogged conditions, the vegetation is dominated by sedges, grasses and heathers such as ling heather, cross-leaved heath, bog cotton, carnation sedge, black bog rush, purple moor grass and deer sedge. Common herbaceous species include tormentil, sundew, bog asphodel, lousewort and milkwort. While bryophytes, especially bog mosses or Sphagnum species, form a significant component of the vegetation, they tend not to form complete carpets as would be typical of raised and mountain blanket bog surfaces. Other blanket bog bryophytes present are the red worm liverwort, black moss and silver-haired moss. Waterlogged habitats on blanket bogs support thick deposits of algae.

This blanket bog vegetation covers extensive areas and is broken up by a variety of natural features. Pools range in size from mere depressions to small lakes. Small Sphagnum-filled pools contain bog bean, bog cotton, bladderwort and sundew. Larger peat-based pools contain American pipewort and water lobelia, species which show unusual world biogeographical distributions. Some of the lakes contain islands which are covered with typical bog plants with the addition of crowberry, juniper and lichens. Sometimes larger islands, especially in Conamara are wooded with trees such as holly, yew, oak, willow and Scot's pine. Interconnecting pool patterns, often dominated by mud sedge and sundew are occasionally recorded. Other features which occur in Atlantic blanket bogs include rock outcrops, dominated by heathery vegetation, rock-bottomed lakes with water lilies and pond weeds, flushes characterised by fen vegetation and drainage channels which may reach to the mineral soil where distinct willow woods or wet meadow communities form a sharp contrast with the adjacent blanket bog vegetation.

There is a considerable difference between the Atlantic blanket bogs of northwest Mayo and those of Conamara. In Mayo the peat is generally deeper and the vegetation is relatively uniform over extensive areas. Most pools and lakes are peat bottomed and flushed areas where water is moving are small and localised. In Conamara the peat is shallower and the lakes are mostly rock basins with peat bottomed-pools being uncommon. The broken terrain and rock outcrops have resulted in a greater degree of nutrient enrichment of the peat and flushes are widespread and often extensive. When these are dominated by bog myrtle, the sweet scent blowing across the bog is wonderful. The region is particularly noted for the variety of heathers such as Mackays heath, Irish heath, St Dabeoc's heath and bell heather.

Mountain blanket bog vegetation is characterised by the presence of species such as crowberry, bilberry ad club moss in the vegetation. Mountain blanket bog also contains many of the species found in raised and Atlantic blanket bog types such as cross-leaved heath, ling heather, bog asphodel, bog cotton and deer sedge. Hummocks of Sphagnum moss and silver haired moss are found with abundant lichens, which are surrounded by Sphagnum pools. There are occasional lakes with bog bean, bottle sedge and bog mosses.

Fauna of Blanket Bogs
There are very few specialist animals, apart from some insects that are dependent upon blanket bogs. To most creatures, blanket bogs are hostile environments, akin to cold deserts with low levels of nutrients, poor shelter and little cover. Consequently they are relatively poor in terms of species diversity and population densities and many species are opportunistic or temporary.

The most likely mammal to be encountered on blanket bog is the Irish hare with a characteristic density of 1 hare per km2. Otters frequent the pools and lakes of blanket bogs, their well-worn tracks being commonly seen, while streams and lakes are important for brown trout and salmon. Other animals that inhabit blanket bogs include frogs, newts, pygmy shrews, red deer, foxes and bats.

The most obvious vertebrates are the birds with species such as skylark, meadow pipit, curlew, red grouse and snipe commonly breeding but in low densities. Golden plover breed on blanket bogs as do dunlin in parts of north-west Mayo and Conamara. Merlin hunt over bogs, usually nesting in adjacent forestry plantations, wooded lake islands or adjacent scrub. A particularly important species is the Greenland white-fronted goose which overwinters only in Ireland and Britain. Small flocks occur in Conamara, north-west Mayo and other undisturbed areas of blanket bog.

Of all the birds that live on peatlands the red grouse is the most characteristic. Red grouse are thinly scattered on blanket peatlands and are dependent on the shoots, buds and flower heads of ling heather for their food source. In north-west Mayo population densities are 2-3 pairs per km2.

Invertebrates are by far the most abundant animals on blanket bogs and certain groups such as the springtails, butterflies, dragonflies and spiders are well represented. Again few species are exclusive to bogs, with the small copper butterfly, large heath butterfly and large marsh grasshopper being exceptions. Aquatic invertebrate communities in bog pools and lakes are simple with bloodworms, water beetles, water boatmen, pond skaters, damselflies and water lice being the principal inhabitants providing food for predators such as dragonfly nymphs and raft spiders.

Living History Books
Stored within the peat, there is the complete record of the blanket bog's history, and much more besides. By taking a downward core cut through the peat, it is possible to determine from the plant remains, many of which look as fresh as the day they died thousands of years ago, what species were growing on the bog at any time. Scientists have been able to link changes in the bog vegetation to shifts in the climate. Bogs also contain pollen grains that have blown onto the surface of the bog from the surrounding vegetation. Analysis of this pollen rain from different layers in the peat reveals the composition of the vegetation on the bog and landscapes further afield. We know from this record that the bogs have always been largely open areas in the landscape while around them a succession of forests have come and gone. The pollen record shows phases when the first farmers began to clear the forests. More direct evidence of man is seen in the buried tracks, shoes, musical instruments, animal traps, boats, coins, whole villages, jewellery and even bog butter and human bodies that have been found preserved in the waterlogged peat.

Blanket Bogs - Valuable Wetlands, not Wastelands
There are a number of scientific, economic, cultural and moral reasons for conserving blanket bogs.
* Only a small amount of blanket bog exists in the world. Ireland possesses 8% of the world's blanket bog and is the most important country in Europe for this type of habitat.
* Blanket bog landscapes provide a refuge for several rare plants, birds and invertebrate species.
* Blanket bogs are commonly used as rough grazing land for sheep and cattle, grouse shooting, deer stalking and fishing.
* Blanket bogs preserve prehistoric farming landscapes beneath the peat as well as a diverse range of artefacts within the peat mass.
* The patterns of pools on the flatter areas of blanket bog is of particular conservation significance. The pools support a specialised range of mosses (especially species of Sphagnum) and plants and they provide essential feeding habitats for wetland birds.
* Within their peat layers, blanket bogs preserve a record of their own growth and development and on a larger scale, they provide insights into regional vegetation change, climate change, atmospheric pollution and act as chronometers for other events such as volcanic eruptions.

Conservation & Protection of Ireland's Blanket Bogs
Blanket bogs originally covered 774,360ha of the land surface in the Republic of Ireland. Extensive survey work has shown that there is only 21% (166,115ha) remaining in a relatively intact condition. Blanket bog has been lost to hand cutting over the last 400 years, mechanised turf extraction schemes since the 1940's, afforestation programmes commencing in the 1950's, intensification of agriculture following Ireland's entry to the European Community in 1973 and the continual process of land reclamation.

The Irish Peatland Conservation Council (IPCC), a non governmental organisation formed in 1982 aims to ensure the conservation of a representative sample of peatland types in Ireland. We work with Dúchas, the state agency responsible for nature conservation, to ensure that all blanket bogs of nature conservation importance are protected. This is the long-term goal of IPCC's peatland conservation strategy.

Dúchas protect blanket bogs in three different ways. Buying blanket bogs ensures full protection and Dúchas currently own 37,000ha of blanket bog. They survey blanket bogs and designate important conservation worthy sites as Natural Heritage Areas, which are protected under the Wildlife Act. Surveys have been underway since the 1980's and today most of the atlantic blanket bogs have been discovered and made into NHAs. Mountain blanket bogs have not been completely surveyed especially in the southern half of the country. This is something that needs to be done as a priority and IPCC are campaigning on this issue. Lastly, in meeting our European obligations under the Habitats Directive, Dúchas designate a representative sample of our blanket bogs as Special Areas of Conservation. To date Dúchas have designated 135,000ha of blanket bog habitat as SACs. With incomplete information on mountain blanket bogs, the number of sites being included by Dúchas in the SAC network is not representative. IPCC have undertaken independent research on blanket bogs and have shown Dúchas and EU officials in our Bogs and Fens of Ireland Conservation Plan that it would be possible for Ireland to designate another 12,500ha of blanket bog to include the full range of variation in the habitat in Ireland. This is a very important issue and it is one that must be resolved between Dúchas, IPCC and
the EU.

Other aspects of the IPCC's peatland conservation strategy are to prevent planning permission for activities that threaten to damage conservation sites and to encourage government to fund better management and rehabilitation of blanket bog NHAs. IPCC raises awareness of peatland conservation through outreach programmes directed at the general public and school children.

Saving Blanket Bogs - What Can You Do?
* Become a member of a conservation organisation.
* Make a donation to the IPCC towards the purchase of endangered blanket bogs.
* Write to TD's asking them to spend more money on nature conservation.
* Visit blanket bog sites and learn more about them.
* Report illegal dumping and any other damaging developments on blanket bogs in your locality or elsewhere to Dúchas or IPCC.

Blanket Bogs to Visit
Connemara National Park, Co. Galway
Glenveagh National Park, Co. Donegal
Killarney National Park, Co. Kerry
Mayo National Park, Co. Mayo
Wicklow National Park, Co. Wicklow

Sources of Information
Dúchas - The Heritage Service, 7 Ely Place, Dublin 2. Telephone (01) 6472360 Web Site: www.heritagedata.ie
Irish Peatland Conservation Council, 119 Capel Street, Dublin 1. Telephone (01) 872 2397. Web Site: www.ipcc.ie

Further Reading
Bellamy, D. (1986) The Wild Boglands - Bellamy's Ireland. Country House, Dublin.
Cabot, D. (1999). Ireland, A Natural History. Harper Collins Publishers, London.
Foss, P.J., O'Connell, C.A. & Crushell, P.H. (2001) Bogs and Fens of Ireland Conservation Plan 2005. Irish Peatland Conservation Council, Dublin.
O'Connell, C. (1987) ed. The IPCC Guide to Irish Peatlands. Irish Peatland Conservation Council, Dublin.

Catherine O'Connell, IPCC