Wetlands are lands covered by water, and include lakes, rivers, marshes, fens, bogs and other water bodies whether natural or artificial, permanent or temporary. The water in wetlands may be still, flowing, fresh, salty or brackish. Wetlands are found throughout the world in low-lying areas in particular, but also in some high areas. They are particularly important in some LEDCs as a source of food (rice paddies, for example, as well as sources of fish and shellfish. Wetlands perform many ecological services such as the purification of polluted waters, the break-down of organic waste, and the prevention of flooding.
Ireland is an extremely wet country, lying in the direct path of moist winds blowing over the Atlantic Ocean. Average rainfall is over 1150 mm per annum. Less than 40% of this evaporates into the atmosphere, so the remaining 700 mm accumulates on the land or runs off to the sea. About one-third of the country is covered with poorly drained soils, which contain large amounts of water. This includes the bogs (peatlands) that cover much of the Midlands and the west of Ireland.
The vegetation of wetlands is very varied and depends on physical factors as depth of water, pH and nutrient content of the water. Upland lakes and mountain streams generally are unproductive and have sparse vegetation whereas lowland lakes and rivers tend to be more productive and have more vegetation.
Succession in wetlands is also evident. There is often a zone of emergent plants by the water’s edge, characterised by common reeds, bulrushes and yellow flag. These may develop into extensive swamps, called reedbeds. Eventually, trees such as willow and alder may grow.
Turloughs are seasonal streams found in limestone areas. They are normally full of water in winter but dry in summer. Raised bogs develop where the vegetation loses contact with the groundwater, and bog mosses develop. Typical plants include bog cotton and sundew. In mountain areas extensive blanket bogs develop.
All wetlands have a valuable role in the environment but certain types need protection, such as bogs, fens, and turloughs. Wetlands are a valuable source of water supply. For example, the River Liffey is dammed at Poulaphuca and provides a large amount of water for Dublin (and for the Guinness brewery!). It also provides some hydro-electric power (HEP). Electricity is also generated by burning peat (or turf) from widespread bogs throughout Ireland, although this practice has been restricted due to the Paris Agreement on climate change (2015).
Many wetlands are under threat due to eutrophication. Other wetlands are at risk due to drainage. Many of the major river catchments of Ireland were drained in the 1970s to make way for agricultural land. Pollution is also increasing due to agricultural run-off. Acidification is a problem in some mountainous areas. Dumping of refuse is a problem related to the expansion of urban areas. Coastal reclamation for agriculture and port expansions are reducing the size of estuarine wetlands. More than 90% of the Midlands raised bogs have been exploited for turf production.
Thus, wetlands in Ireland provide many important ecological services, although they have been severely reduced in size and quality although there is increasing awareness about their benefits and importance.