Nutrient Pollution of Peatlands

Peatlands are wetlands that feed into the river catchment for their area. Wetlands provide many important functions including water supply, flood water storage, pollution control, groundwater recharge, habitats for wildlife and are a major resource for fisheries, water sports and recreation. Damaging activities carried out on peatlands or within the water catchment area of peatlands, such as peat extraction, overgrazing, afforestation and farming, will inevitably lead to water pollution and have serious consequences for the services wetlands provide.

Fens are particularly vulnerable to nutrient pollution as they often occur in more intensely managed landscapes than other peatland types. Part of their water supply is derived from ground water and once this is polluted it can remain so for a long time. The availability of nutrients such as nitrogen (N), phosphorous (P) and potassium (K) are of key importance to plant growth and vegetation composition in fens. Eutrophication of fens (i.e. enrichment with N, P, or K) is widely regarded as an important cause of vegetation change (with a loss of species richness in particular) within fens in northwest Europe. The Monaghan Fen Survey (Foss and Crushell, 2007) provides useful baseline data on the nutrient status of fen surface waters against which monitoring of other fen types can be compared. In the survey the results confirmed that alkaline fen sites are dependant on a continual supply of calcium rich groundwater. In contrast, vegetation that occurs on transition mires is dependant on less mineral rich groundwater, with a circumneutral pH.

Large amounts of nutrients entering the surface water or ground water, from local sources, such as farming runoff, fertilisation or septic tanks, if intensive or prolonged lead to eutrophication of the fen habitat. This nutrient enrichment can be seen by the proliferation of nutrient loving large sedge species such as Great Pond Sedge (Carex riparia) in fen habitats and a reduction in small sedges and other fen species as a whole. This causes habitat destruction and the loss of species sensitive to nutrient enrichment such as the Whorl Snail (Vertigo moulinsiana). Doyle and Ó Críodáin (2003) have identified phosphorous as the limiting nutrient to growth in most fens and elevated levels lead to vigorous growth of grasses over other species and loss of fen species. The overall result is the loss of species biodiversity.

The Monaghan Fen Survey (2007) surveyed 42 sites, 25 of which were found to contain fen habitat. The survey identified 5 sites where changes in vegetation were noted and ascribed to the effects of pollution, while a further 10 sites were considered to be potentially under threat from pollution. Factors causing the pollution were the intensive management of the land surrounding the fen for silage production and runoff from cattle grazing. IPCC’s records of fens of conservation importance show that 55 sites are currently affected by pollution or have been damaged by pollution in the past (see the table inset).

The table shows the number of peatland sites of conservation importance in the Republic of Ireland that have been damaged by water pollution. Source: IPCC Sites Database 2009.

Peatland Habitat Number of Sites
Fen  55
Raised Bog  11
Blanket Bog  1
Total  67

Curtis et al, (2006) have identified several ground-water fed peatlands which are vulnerable to eutrophication, including transition mires and quaking bogs, calcareous fens with Cladium mariscus, petrifying springs with tufa formation and alkaline fen. They have noted on calcareous fens with Cladium mariscus that eutrophication, without drying may result in the invasion of Typha and Phragmites. With drying, the diversity of aquatic macrophytes declines and coarse fen vegetation species may invade. Management of the wider countryside is needed if the eutrophication of fen habitats is to be controlled. For example, the use of constructed wetlands to treat waste water from intensive agriculture and village housing schemes may contribute to the reduction of eutrophication within the catchments of sensitive wetlands.

Pollution also occurs on blanket and raised bogs but it is much less of a threat than it is to fen habitats. IPCC have a record of the pumping of farm slurry onto the centre of Arraghmore Bog NHA in Co. Tipperary.

Activities carried out on peatlands, such as overgrazing, peat extraction and afforestation, can also have detrimental affects on water quality within local river catchments and on aquatic biodiversity. Overgrazing of a peatland leads to changes in the species composition and may lead to the creation of bare peat. This is followed by damage to the peat soil caused by compaction and results in erosion of peat. In severe cases overgrazing may cause a “bog burst”. Mechanical peat extraction by private individuals and industry can lead to the deposition of peat silt in waterways. Peat sedimentation in salmonid and pearl mussel rivers is detrimental.

The widespread afforestation of peatlands has taken place since the 1950’s, particularly in lowland and upland blanket bog. Drain installation, aerial fertilisation and the growth of conifers can impact on the peatland and on the local river catchment by increasing siltation, eutrophication and acidification. To comply with the Sustainable Forestry Standard Code of Best Forest Practice a species action plan for the Freshwater Pearl Mussel (Margaritifera margaritifera and Margaritifera durrovensis) is being produced. This species action plan contains a programme of measures, which aim to protect water quality by reducing the adverse impacts of peatland disturbance on water quality.

The Water Framework Directive

The Water Framework Directive (WFD) is to become the definitive directive in water quality management across the EU. IPCC are hopeful that its objectives will have positive effects in the management of nutrient enrichment in peatlands and river and wetland catchments. 
The main objectives of the WFD are to be achieved by putting in place a River Basin District Management Plan setting down actions to achieve good status in surface waters and groundwater by 2015 in each of the eight river basin districts in Ireland. Some of the stated objectives of the WFD include the protection and enhancement of the status of all our waters, the reduction or phasing out of the discharge of dangerous substances to watercourses, the establishment and maintenance of a register of ‘protected areas’ and the streamlining of legislation.

The WFD seeks to prevent further deterioration of groundwater fed wetland quality by ensuring existing legislation provides for their protection and enhancement. This action will ensure that “good ecological status” is achieved. In relation to wetlands the Water Framework Directive also aims to prevent their “further deterioration”.

The priority actions for tackling the issue of nutrient pollution on peatlands in the Republic of Ireland are set out in the table below:

Actions Needed to Control Invasive Species on Peatlands Priority Timescale
Short (0-3 years)
Medium (3-5 years)
Long (5-10 years)
Reverse the negative impact of peatland enrichment and pollution on water quality through the inclusion of management and restoration measures in the River Basin District Management Plans.  Medium Short
Use constructed wetlands and permaculture technologies to reduce the impact of intensive farming pollution on the surface water catchment of fens and other wetland habitats.  Medium  Medium
Farmers operating within the surface water catchment of fens should be encouraged to enter REPS.  High Medium
Identify threats to wetlands and develop and implement policies that will safeguard wetlands. Threats may include inappropriate drainage and development, changes to hydrology, pollution, eutrophication and abstraction.  High  On-going
Ensure that groundwater fed wetlands are protected from abstraction or pollution of the ground water so as to comply with the WFD.  High On-going
Monitor all fens designated for nature conservation in Ireland regularly for their nutrient status. At the very least a representative sample of the different fen types. e.g. transition mire, alkaline fen and calcium rich fen should be monitored.  High On-going
Make hydro chemical analyses a mandatory element in the NPWS county-by-county fen survey.  High Medium

Source Citation

Malone, S. and O’Connell, C. (2009) Ireland’s Peatland Conservation Action Plan 2020 – halting the loss of peatland biodiversity. Irish Peatland Conservation Council, Kildare.

Expanding on the Content of the IPCC Action Plan 2020

Please follow the links below to further information from the IPCC Action Plan 2020.

Peatlands 2020 Action Plan Summary Extent and Utilisation of Irish Peatlands Designation of Peatlands of Conservation Importance Climate Change & Irish Peatlands Peatland Site List of Conservation Importance in Ireland
Halting the Loss of Biodiversity Peatland Habitat Loss Over-Exploitation of Peatlands for Peat including the Cessation of Turf Cutting on Peatlands Nutrient Pollution of Peatlands Invasive Species & Peatlands


Copies of Ireland’s Peatland Conservation Action Plan 2020 – halting the loss of peatland biodiversity cost €25 and may be ordered from the Nature Shop

Text, Photographs and Images © Irish Peatland Conservation Council, Bog of Allen Nature Centre, Lullymore, Rathangan, Co. Kildare. Email:; Tel: +353-45-860133.