bogs

bogs, regionally widespread and locally extensive deposits of peat of varying but, in geological terms, recent post‐glacial origin. Bogs are estimated to have covered up to 3 million acres, or approximately one‐seventh of Ireland's land area in the past. They have acted, variously, as a major constraint on the human exploitation of the Irish environment during later prehistoric and early historic times and, in more recent centuries, as a reservoir of colonizable land and as a source of fuel.

Irish bogs have been classified in various ways according to the environmental conditions in which they originated and the relative importance of the climatic and other factors which promoted their development. The most commonly used classification distinguishes between raised bogs and blanket bogs. Raised bogs occur widely in lowland areas in the Irish midlands, east of the Shannon and Suck rivers, and in the north. They first began to develop between 10,000 and 7,000 years BP (before present), and are termed ‘raised’ because of their manner of growth. As existing lakes are colonized by fens and marshes, so deep layers of fen peat build up, eventually creating base‐deficient conditions which permit invasion by more acidic plants such as sphagnum moss. These mosses grow into small hummocks, which dry out and are colonized by heathers. The pools created between these hummocks attract further sphagnum colonization, and the process is repeated, progressively raising the bog's surface. Continued growth depends on adequate rainfall and vegetable debris, but once begun is self‐perpetuating.

Blanket bogs first developed rather later during the prehistoric period, from c.5,500 years BP, and in the specific context of early woodland clearance and agricultural land use in upland areas at a time when Ireland's climate may have been becoming wetter. The modern distribution of blanket bog is much less extensive than it originally was, but still runs in a discontinuous arc from the Sperrin mountains in Co. Londonderry, south through the coastal uplands of western Connacht, to west Cork and Kerry in the far south‐west. Elsewhere it is confined to mountain ranges such as the Mournes, Wicklows, and Knockmealdowns.

The development of blanket bogs depended on the existence of podzol soils, which were characterized by an impervious iron pan. This impeded drainage within the soil and led to waterlogging and the growth of rushes. Eventually, these rushes built up a mineral‐deficient layer of peat liable, as in raised bogs, to invasion by sphagnum moss. With continued waterlogging the rushes spread and the ground finally became buried under a blanket of acidic peat.

The discovery in the west of Ireland of numerous neolithic and Bronze Age field walls, tombs, and scratch‐plough ridges beneath these blanket bogs, for example at Belderg and Bunnyconnellon, both in Co. Mayo, demonstrates the extent to which their growth curtailed early agriculture. Throughout the early Christian and medieval periods they remained beyond exploit‐ation by contemporary agricultural technology. Only with the rise in population since the early modern period, and improvements in drainage, have bogs come to be regarded as land to be reclaimed rather than wasteland to be avoided. During the immediate pre‐Famine period, many bogs on the margins of cultivation in the west of Ireland were colonized by smallholders and squatters, driven there by the locally extreme pressure of population on relatively limited land resources. Subsequently, with the collapse of Ireland's population after the Famine, these areas were abandoned.

Turbary rights represent an equally historic form of exploitation. Traditionally, the right to dig peat or ‘turf’ for fuel constituted an important element in leasehold agreements between landlords and tenants. Yet turf was never widely exploited as an industrial fuel, manufacturers in Dublin, Cork, and Belfast preferring to import coal. Various reasons have been adduced for this. Although cheaper than coal, turf had only half its calorific value and was as bulky to transport, while its production could be halted by wet weather. In the present day, by contrast, domestic rights of turbary survive, but exist alongside the commercial exploitation of bogs in Co.Mayo and the midlands for both horticulture and fuel. Ex‐periments to generate electricity from peat fol‐lowed the rise in demand for native fuels during the First World War, and peat production was nationalized in 1946 (see bord na móna). By 1970, 135,000 acres of bog were yielding 4 million tons of peat per annum, and turf‐generated electricity amounted to 20 percent of demand.

Bibliography

Mitchell, F. , Shell Guide to Reading the Irish Landscape (2nd edn., 1986)

Lindsay Proudfoot