Blanket Bog

Bogs are areas of waterlogged ground where dead plant material can’t fully decompose. Because of the waterlogged conditions, plants only partially decompose to form a brown substance called peat. Plants that are tolerant of the waterlogged conditions such as Sphagnum mosses grow on the surface of the peat. As these plants die off they add to the peat so that the peat continues to accumulate. This process has been taking place over thousands of years and has resulted in an extensive blanket of peat over lowland areas and mountain slopes (this blanketing phenomenon is what gives blanket bogs their name). The depth of the peat is typically between 1.5 and 7m deep and is dependent usually on the steepness of the slope with peat on flatter ground often being considerably deeper than that found on sloping ground.

Bog Pool at Srahduggan (Photo Nicola Carroll)

County Mayo has a particular type of blanket bog known as Atlantic or oceanic blanket bog. This type of blanket bog is different from that found on the eastern side of the country because the bog develops on the lowland right up to the coastline. This occurs because of higher levels of rainfall along the Atlantic coast than in other parts of the country.

Sundew and Damselfly © NPWS

Conservation Status

Classifications of bog which can be found in the National Park based on the Heritage Council’s classification of habitats:

• Upland blanket bog 

• Lowland blanket bog 

• Cutover bog 

• Eroding blanket bog 

Classifications of bog with can be found in the National Park and which require protection, as described in the EU Habitats Directive - Annex II:

• Active blanket bog* 

*This is a priority habitat under the Habitats Directive.


Conifer Plantation

Conifer Plantations are large uniform stands of non-native evergreen trees such as Sitka Spruce (Picea sitchensis), and Lodgepole Pine (Pinus contorta), that were planted on a commercial basis for their timber. They support a smaller diversity of plant and animal species compared to native forests, but they provide shelter to Red Deer (Cervus elaphus), and are important habitat for Pine Marten (Martes martes). Conifer plantations are also important to birds, such as Tits (Parus spp.), Woodcock (Scolopax rusticola), Crossbill (Loxia curvirostra), and Merlin (Falco columbarius).

Conifer Plantations increase acidity levels in the groundwater which impacts on invertebrate and fish-life in downstream freshwater habitats. The Owenduff bog is unique in Ireland in that it has no upstream conifer plantations.

Pine marten © NPWS

Conservation Status

Classifications of Conifer Plantation which can be found in the National Park based on the Heritage Council’s classification of habitats:

• Conifer plantation


Fens and Flushes

Fens are peat-forming wet areas. They differ from bogs in that they are mostly fed by water flowing through the ground or flowing on its surface rather than by rainfall. This water picks up additional nutrients on its way which enables plant species that require higher nutrient levels to survive in fens. These plants would not survive in nutrient poor bogs.

Marsh Saxifrage (Photo Nicola Carroll)

Flushes are usually smaller features that are maintained by the movement or seepage of water. They occur on slopes and may or may not be peat-forming. One very rare species of flower, the Marsh Saxifrage (Saxifraga hirculus), can only be found in such flushes.

Conservation Status

Classifications of fens and flushes which can be found in the National Park based on the Heritage Council’s classification of habitats:

• Poor fen and flush. 

Classifications of fens and flushes with can be found in the National Park and which require protection, as described in the EU Habitats Directive - Annex II:

• Transition mires and quaking bogs.


Grassland

Grasslands are dominated by grass species but flowering broadleaved herbs and dwarf shrubs do also occur. Grasslands occur in areas where the soil is relatively free draining, usually on slopes where the soil doesn’t become waterlogged. Grasslands are dependent on a certain amount of grazing to prevent them from developing into heaths and scrubs.

Grassland on Slopes of Nephin Beg (Photo Nicola Carroll)

The grasslands of the Park are classified as natural grasslands as opposed to semi-natural or improved grasslands where fertilisation or cutting occurs, such as on farms. In spring the grasslands of the Park come ablaze with flowers and are an important habitat to many different types of invertebrates, such as butterflies and beetles. Due to intense grazing by sheep over recent decades many areas that were previously heaths have become grassland. The National Parks and Wildlife Service is working to restore these heaths by reducing the number of grazing sheep in these areas.

Small Heath Butterfly (Photo: Mike Brown Photography)

Conservation Status

Classifications of grassland which can be found in the National Park based on the Heritage Council’s classification of habitats:

• Dry-humid acid grassland 

• Wet grassland


Heath

Heath derives its name from heather which is a group of small woody shrubs, the most common species being Ling (Calluna vulgaris), Bell Heather (Erica cinerea), and Cross-leaved Heath (Erica tetralix). Found commonly on slopes where the soil doesn’t become waterlogged, heather can dominate whole mountain sides. Heath is an extremely important habitat for Red Grouse (Lagopus lagopus scoticus), a bird which is almost completely dependent on heather as its primary food source.

The Nephin Mountains are also home to another type of heather called Irish Heath (Erica erigena), which in Ireland is only found in west Co. Mayo and Co. Galway. Heathers add a purple hue to the mountains when they flower in the late summer but the Irish Heath is again unusual in that it normally flowers in late winter and spring.

Irish Heath (Photo Nicola Carroll)

Many of the heaths in the National Park have suffered in recent decades from intense sheep grazing to the point that all the heather was lost in certain areas and the Red Grouse population suffered as a result. The National Parks and Wildlife Service now have agreements in place with flock owners to reduce sheep numbers on the mountains to enable the heaths to recover.

Conservation Designation

Classifications of Heath which can be found in the National Park based on the Heritage Council’s classification of habitats:

• Dry siliceous heath 

• Wet heath 

• Montane heath 

Classifications of Heath which can be found in the National Park and which require protection, as described in the EU Habitats Directive - Annex II:

• Northern Atlantic wet heaths with Erica tetralix 

• Alpine and boreal heath 

• Juniperus communis formations on heaths or calcareous grasslands


Lakes and Ponds

Lakes and ponds are enclosed bodies of freshwater which vary in size from small pools out on the open bog to large lakes which have formed high in the hollows of mountain corries. Corries are hollows found on mountainsides which were carved out by the action of glaciers during the last Ice Age. The water in the lakes comes from rainfall, either falling directly into the lake or a as a result of percolating through the brown peat of the surrounding bog. As it percolates, the water becomes acidic and acquires a dark colour.

Lough Drumderg (Photo Cameron Clotworthy, NPWS)

The largest lake within the Park is a corrie lake and is named Corryloughaphuill which is an anglicisation of the Irish name Coire Loch an Phoill, meaning “the corrie lake of the two hollows”. Lough Anaffrin is the main water reservoir for the Ballycroy area. The lake’s name is an anglicisation of the Irish Loch an Aifrinn, which means “the lake of the mass”. This is where Catholics held mass in secret during Penal Times.

Scardaun Loughs (Photo Cameron Clotworthy, NPWS)

Conservation Status

Classifications of lakes and ponds which can be found in the National Park based on the Heritage Council’s classification of habitats:

• Dystrophic lakes 

• Acid oligotrophic lakes 

• Reservoirs 

Classifications of lakes and ponds which can be found in the National Park and which require protection, as described in the EU Habitats Directive - Annex II:

• Natural dystrophic lakes and ponds 

• Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea.


Rivers and Streams

Due to high levels of rainfall in Ballycroy National Park the slopes of the mountains are lined with mountain streams. The steep gradient and high water levels cause the streams to be highly erosive, cutting valleys into the mountain slopes. On lower ground these streams converge into the larger rivers in the Park such as the Owenduff River and the Tarsaghaunmore River which meander their way through the bog.

Waterfall at Scardaun Loughs (Photo Leonard Floyd)

These rivers are relatively shallow but their levels rise quickly after rainfall and can be extremely treacherous to cross. The water is dark coloured as a result of rainfall percolating through the peat of the bog. This dark colour is what has given the Owenduff its name, Owenduff being an Anglicisation of the Irish Abhainn Dubh, which means “the black river”. The rivers are particularly important as a breeding ground for Atlantic Salmon (Salmo salar), which migrate from the open sea back to the river in which they were originally spawned, to repeat the breeding cycle.

River flowing through Ballycroy National Park © NPWS

Conservation Status

Classifications of rivers and streams which can be found in the National Park based on the Heritage Council’s classification of habitats:

• Eroding/upland rivers 

Classifications of rivers and streams which can be found in the National Park and which require protection, as described in the EU Habitats Directive - Annex II:

• Water courses of plain to montane levels with the Ranunculion fluitantis and Callitricho-Batrachion vegetation 

• Habitat of the Annex II species Otter and Atlantic Salmon