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Provided by the author(s) and University College Dublin Library in accordance with publisher policies. Please cite the published version when available. Title Lowland Bogs, Fens and Reedswamps Authors(s) Bracken, Fintan; Smiddy, Patrick Publication date 2012 Publication information Nairn, R. & O'Halloran, J. (eds.) Bird Habitats in Ireland Publisher The Collins Press Link to online version http://www.collinspress.ie/bird-habitats-in-ireland.html Item record/more information http://hdl.handle.net/10197/7327 Downloaded 2021-09-24T17:54:02Z The UCD community has made this article openly available. Please share how this access benefits you. Your story matters! (@ucd_oa) © Some rights reserved. For more information, please see the item record link above. 7. Lowland Bogs, Fens and Reedswamps Fintan Bracken1 and Patrick Smiddy Introduction Peatlands are one of the most characteristic landscape features in Ireland and everyone is familiar with the large raised bogs of the Irish midlands and the blanket bogs of our uplands and Atlantic coast. Peatlands cover between 17% and 20.6% of the total area of Ireland, a percentage exceeded in Europe only by Estonia (22%) and Finland (30%) (Hammond 1981; Lappalainen 1996; Aalen et al. 1997; Connolly and Holden 2008). This chapter will deal with two of the main types of bogs found in Ireland, raised bogs and fens, while blanket bogs will be dealt with in Chapter 8: Upland heath and blanket bog. Reedswamps often occur in association with fens but they are not dependent on groundwater and can also occur in other situations, both freshwater and tidal. Raised bogs cover approximately 314,000 ha of the land surface of Ireland and are typical of the central plain of the country (Aalen et al. 1997). Raised bogs were formed where shallow lakes were overgrown by vegetation, which subsequently led to plant debris accumulating to form peat (Hammond 1981). Fens are peat-forming systems that are fed by groundwater or moving surface waters (Fossitt 2000). Fens can be found nearby springs and seepages, on river flood plains, in flat basins and in glacial lake beds. True intact fens are rare in Ireland as they have mostly been reclaimed for agriculture. Reedswamps are distributed throughout the country, on the coast as well as inland, often in association with other habitats such as rivers, lakes, estuaries and coastal lagoons. They are especially associated with the major rivers such as the Shannon, and the larger lakes such as Lough Neagh. Most reedswamps are dominated by one or two tall grasses or sedges. Common reed depends on regular flooding but it can tolerate occasional drying out in summer. It can survive in both fresh and brackish waters. Many reedswamps begin as shallow lakes, and through succession develop into fens. This process occurs through a gradual build up of peat from dead plant material, which raises the surface out of reach of ground water. While reedswamps are dominated by one species, the common reed, fens, in turn, develop shorter and more diverse vegetation, which may include typical species such as meadow sweet and ragged robin. Over longer periods of time fens further develop into woodland dominated by alder, willow and birch with a luxuriant ground flora (Anon 1974). The grazing of farm animals may alter and reduce the vegetation in some reedswamps and fens. Common reeds may also occur in drier 1 Fintan Bracken’s research for this chapter was funded by the Environmental Protection Agency through the project “BOGLAND: Protocol for Sustainable Peatland Management in Ireland” (see Renou-Wilson et al. (2010) for more details). Page 1 of 19 7. Lowland bogs, fens and reedswamps habitats on the higher mudbanks of tidal rivers, such as the Blackwater (Munster). Unfortunately, to the casual visitor these habitats often appear ‘empty’ as many of the bird species that live in them are skulking in nature. This perception makes them vulnerable to damage as they are often viewed as wastelands. Historically, these wetlands have been exploited, especially through drainage programmes in the 19th century, and the arterial drainage schemes of the 20th century. Few such lowland wetlands remain untouched, and much of our present agricultural grassland is based on former fens and reedswamps. Over the last 20 years, during the economic boom, many of the remaining wetlands suffered further damage due to filling with rubble and builder’s waste. Sustainable exploitation of some wetlands takes place on a small scale, such as the harvesting of reeds for thatch, and rushes and willows for basket making. A high proportion of Irish peatlands has been damaged in varying degrees during the last sixty years due to several factors. These include the introduction of large- scale, mechanised turf extraction schemes in the 1940s for fuel and horticultural peat, afforestation programmes commencing in the 1950s, intensification of agriculture following Ireland’s entry to the EU and land reclamation (Feehan and O’Donovan 1996). The area of peatland suitable for conservation in Ireland has been seriously reduced in recent times leaving less than 15% of the original extent shown in Hammond’s peatlands map of Ireland (Hammond 1981) in near- intact condition (Crushell 2002; Foss 2007; Douglas et al. 2008). The importance of raised bogs and fens as habitats in an international and national context is illustrated by the inclusion of both in Annex I of the EU Habitats Directive. This affords special conservation status to peatland habitats including active raised bogs, degraded raised bogs still capable of natural regeneration, calcareous fens with Cladium mariscus and species of the Caricion davallianae, and alkaline fens. Many important raised bog and fen sites in Ireland are allocated special protection through their designation as Nature Reserves, Special Areas of Conservation (SAC), Special Protection Areas (SPA), Natural Heritage Areas (NHA) and Areas of Special Scientific Interest (ASSI). Raised Bogs The numbers of bird species occurring on raised bogs during the breeding season is quite low and is often lower than blanket bogs (Madden 1987b; Hutchinson 1989; Feehan and O’Donovan 1996; Wilson 2002). Only eleven species were found during the breeding season at three midlands raised bogs (Sharavogue and Clara, Co. Offaly and Carrowbehy, Co. Roscommon) with meadow pipit and skylark dominating the bird community of this habitat with 62% and 30% of the birds recorded respectively (Bracken et al. 2008, Table 7.1). Other common species of raised bogs in the spring and summer are curlew, snipe, mallard and wren (Bracken et al. 2008, Table 7.1). Red grouse also occur on raised bogs where its main food, heather, occurs in sufficient abundance but the species is more typical of blanket bogs (Bracken et al. 2008) (See Chapter 8: Upland heath and blanket bog). Several species of raptor including peregrine, kestrel and merlin may hunt over raised bogs with merlin often establishing breeding territories on raised bogs (Wilson 1990; Norriss et al. 2010). Other surveys of breeding birds of raised bogs have also been conducted with 17 breeding species found within the Dunkellin/Lavally river catchments, Co. Galway (Buckley and McCarthy 1987). Four breeding species of wader, golden plover, lapwing, snipe and curlew were found by Partridge (1988) during a survey of 95 Page 2 of 19 7. Lowland bogs, fens and reedswamps raised bog sites mainly in Co. Tyrone as part of the Northern Ireland breeding waders survey. Only two breeding species, meadow pipit (20 territories) and skylark (15 territories), were found to be wholly associated with the intact raised bog habitat during a survey of the intact dome of Dunloy Bog ASSI in County Antrim in 2004 (Allen and Mellon Environmental 2007). Another species, curlew, included the bog within its territory but nested and did most feeding in the lagg area and adjacent grasslands (Allen and Mellon Environmental 2007). Twenty-one breeding species were recorded at Finn Lough in Co. Offaly which is sandwiched between an esker ridge and a cutover bog (Rochford 1988). The bird community of an area of intact raised bog in Mongan Bog, Co. Offaly comprised twelve different species including kestrel, redshank and linnet but only mallard, snipe, skylark and meadow pipit were proven to have bred and curlew was suspected of nesting (Madden 1987a). Table 7.2 (modified from Wilson 1990) summarises some of the findings from these studies of the birds of raised bogs in Ireland during the breeding season and illustrates that both species diversity and densities are low in this habitat. Detailed studies were carried out on the dispersion patterns and habitat use of ground-nesting bird species on three raised bogs in Co. Offaly, All Saint’s Bog, Clara Bog and Raheenmore Bog in the mid 1990s (Huvendiek 1996; Pohler 1996). A territory mapping study of 266 ha of Clara Bog found 14 breeding species in the relatively intact western part, with skylark being the most abundant with 82 territories followed by meadow pipit with 81 (Pohler 1996). The eastern part has been seriously disturbed by a network of surface drains and only had nine breeding species with meadow pipit being the most abundant with 72 territories and skylark with 52. Pohler (1996) only regarded four of the recorded breeding bird species (meadow pipit, skylark, snipe and curlew) as typical breeders in open raised bog habitats. The study also examined the dispersion patterns of breeding birds and their habitat relationships in Clara Bog (Pohler 1996). Skylark and meadow pipit showed no distinct response to site-specific differences in habitat properties, indicating their unspecialised mode of habitat use in open raised bog habitats. However, occupied meadow pipit areas of the peatland had higher and denser grass/sedge-dwarf shrub vegetation that unpopulated parts. There was very little difference between occupied and unoccupied areas of the peatland in the case of skylark.