Sperrin Mountains Biodiversity Profile

In the following account of this LCA it should be noted that for consistency, the biodiversity section follows the standard order for all LCAs even though some of the communities discussed later may have more importance for biodiversity than those discussed earlier.

Key Characteristics

• dominated by vast stretches of blanket bog of great complexity including cut-over, drained and eroded peatland
• large coniferous forests have been planted on peat
• nevertheless there are some large areas of intact blanket peatland
• rare montane communities on the highest summits
• broadleaved woodland scarce but the LCA contains part of one of the largest upland oakwoods in Northern Ireland

Woodlands

Woodlands occupy approximately 7% of the LCA; conifer forests form the vast majority. Sitka spruce is the dominant species accounting for between 70% and 95% of trees in Banagher and Altbrittain Forests. Ligfordrum Forest has a more even division with Sitka spruce accounting for around 50% of the trees planted and lodgepole pine about 40%. In addition to these large State Forests, there are several small (c. 1 ha) plantations scattered over the hillsides that are also dominated by Sitka spruce. Some of the largest areas of intact upland blanket peat in the LCA are alongside forests - for example at Brown Hill (see blanket bog below). The Northern Ireland Priority Species, red squirrel is recorded for the forests.

Broadleaved semi-natural woodland is relatively scarce, occupying less than 1% of the LCA, but there are some sites of major conservation importance. Banagher Glen is the most notable example, but only the upstream parts of the wood are included in this LCA. Banagher Glen ASSI, (also cSAC, NNR) as a whole, is the largest surviving intact block of semi-natural woodland in Northern Ireland and the finest example of acid upland oakwood found. The underlying geology gives rise to a wide range of growing conditions ranging from strongly acid to flushed, base-rich. As a consequence, the site is one of the most biologically diverse woodlands in Northern Ireland. The steep sides of the glens are clothed by mature trees, mostly of oak and ash, with an understorey of rowan, hazel, hawthorn and holly. In wetter parts alder and willow may be found. Ferns and mosses are common along the riverbanks whereas drifts of primroses, bluebells, wood sorrel and wood anemone occur in the herb layer. The silver-washed fritillary butterfly, common hawker dragonfly and red squirrel are amongst a rich fauna. The history of this wood is unclear but it appears that oaks were felled around 1770 although allowed to regenerate. The rich ground flora may also contain some species indicative of an ancient woodland site.

A small oak woodland also occurs at Sluggada Burn, but generally the streamside woodlands are of birch with hazel, oak and alder; an example is along the Legnavadder Burn where skylark and spotted flycatcher have been recorded. Some of these streamside woodlands have been 'landscaped' with the planting of beech and occasional conifers. More clearly mixed woodlands are at the Glenrandal River and at Tamnagh Lodge.

Grassland and Arable

Only along the extreme western border and to the north of Plumbridge does agricultural land become dominant. It is almost entirely of improved pasture, but that is of variable quality with some sown pastures reverting to rushes, especially on the upper limits of the agricultural land and on the more heavily gleyed soils. Hedgerows often reflect the neglected character of the fields; they are gappy or overgrown and with whin extending into the fields. The corncrake was recorded in 1988 in the Cavanlee area and the curlew also occurs in the damp grasslands of the upper margins of the neglected agricultural land.

Heaths and Bogs

Blanket peat dominates the LCA, as noted above agricultural land is dominant only along the extreme western border and to the north of Plumbridge. The blanket peat shows an extremely complex mix of intact bog, erosion and cutting; it is difficult in the field to see any clear pattern of occurrence of these types. However, maps of the peatland types show that areas of hagging follow the spine that links the separate peaks of the High Sperrins. These areas are usually above 400m although there are patches where very steep slopes have prevented peat formation, as on Sawel and Dart Mountain. On the moderately steep slopes of spine, peat is extensive but most has been gullied. A high proportion of the plant cover in these areas is of purple moor grass. Intact blanket bog is found mainly on flatter areas at intermediate altitude and on long spurs, as for example on the south side of the mountain ridge above the Glenelly River. The belt of gullied and intact bog is succeeded down slope by a generally continuous belt of cut-over peat whose lower boundary marks the present limit of blanket peat; this limit may have been lower in the past because in some parts cut-over peatland has been reclaimed into enclosed fields.

Northern Ireland has a high proportion of both the UK and Irish blanket bog and is therefore of national importance and, because it is a habitat limited to the north-western fringes of Europe, is of significance to European conservation. It is particularly important that remaining intact bog should be conserved. Generally in this LCA, intact bogs are small, less than 20 ha, but there are some notable extensive areas, including Brown Hill (east of Banagher Forest), Balix Lower and Graignagapple. However, there are threats to the intact bog; for example, overgrazing is evident in some areas. A high heather cover is characteristic of some of these upland blanket bogs and overgrazing has considerably reduced the heather cover as has too frequent burning. In other areas heather management has been poor and it has grown too lank. Some intact bogs have been lost or modified by the cutting of drains either for potential forestry or to improve the grazing. More recently, machine peat extraction, usually found on cut-over peat, has extended onto the intact bog in some locations, for example to the west of Craigatuke and at Legalougha Bridge.

Of particular interest in the LCA are the examples of montane communities - these are rare in Northern Ireland. Dart and Sawel Mountains ASI has cowberry occurring with bilberry and heather forming a plant association which is not only rare in Northern Ireland but is declining (Montane heath). Where peat has been removed the underlying rock comes to the surface; stiff sedge, starry saxifrage and least willow are present. Cloudberry has been recorded to the west of Dart and Sawel on the north facing slopes of Mullaghclogha - the only site for the species in Ireland. This montane habitat is open to grazing pressures as well as to trampling by hill walkers.

Wetlands and Lakes

There are no major standing waters of any biodiversity interest in the LCA. Most rivers support populations of otter. Some streams flowing down the south slopes of the High Sperrins into the Glenelly, a salmonid river, pass through areas of peat cutting. Although agricultural effects on rivers may be relatively minor in this LCA because of the limited amount of agricultural land, single incidents of leakage of slurry, sheep dip or silage effluent can have disastrous effects on river life.

Key Issues

General actions for UK and NI Priority Habitats and Priority Species are detailed in the Habitat Action Plans and Species Action Plans.

WOODLANDS

Issue: coniferous plantations of low biodiversity value are dominant but this LCA also includes the finest example of acid upland oakwood found in Northern Ireland.

Actions:

• enhance the biodiversity value of broadleaved semi-natural woodlands through control of grazing to foster regeneration e.g. along streams; by encouraging replanting of canopy trees; by preventing further loss of woodlands through felling; by retention of fallen and veteran trees (particularly for bryophytes, ferns, fungi and fauna)
• encourage Forest Service in their moves to restore conifer planted areas to broadleaves in their 'Plantations on Ancient Woodland Sites' programme and through other appropriate grant scheme
• further study of the history and ecology of Banagher Glen ASSI and other broadleaved woodlands, as a key to future management
• ensure protection of broadleaved woodlands, particularly from clearance of wet areas of woodland and hazel scrub.

Issue: forestry plantations may threaten intact blanket bogs

Actions:

• discourage small scattered plantations which are intrusive and add little to the biodiversity of peat slopes.
• protect adjacent areas of intact upland blanket bogs by discouraging drainage which may affect water regimes and nutrient levels to the detriment of peatland; by discouraging the spread of fertilisers which can increase the low nutrient levels demanded by bog species; and by discouraging future felling and replanting which could affect hydrology.

GRASSLAND AND ARABLE

Issue: low biodiversity improved pastures but NI Priority Species Curlew is present.

Actions:

• maintain and improve field boundaries especially hedgerows. This may be achieved through adoption of correct cutting cycles; hedge laying and replanting where necessary; leave saplings uncut to develop into hedgerow trees; avoidance of spraying with fertiliser, slurry, herbicides; provision of wildlife strips and conservation headlands around fields; and limitation of field amalgamation
• encourage (through participation in Environmental Schemes) adoption of less intensive management of pastures to allow reversion to more species-rich grassland and protect unsown areas of species-rich grassland, in particular wet grasslands; thus prevent drainage, fertilisers etc.
• limit the expansion of forestry onto abandoned/less-managed grassland so that it does not reduce area of grassland used by bird Priority Species
• monitor the spread of gorse scrub into abandoned/less-managed fields

HEATHS AND BOGS

Issue: intact blanket bogs of national and international remain under threat

Actions:

• maintain the integrity of intact blanket bogs by for example, preventing new forest planting, infilling, fly-tipping, fires, new drainage and extensions of machine cutting onto existing bogs
• consider whether any cut-over bogs could be restored through appropriate water level management, removal of any individual colonising trees and phasing out peat cutting; prevent reclamation of cut-over peatland into enclosed fields
• the presumption against new conifer planting on bogs should be retained for any planting schemes by Forest Service, farmers or landowners

Issue: NI Priority Habitat Montane heath is rare and declining in Northern Ireland

Actions:

• encourage farmers to join the ESA Scheme; protect existing heather from overgrazing; ensure suitable burning or flailing to return lank heather to shorter denser shrubs consider new educational efforts to discourage mechanised peat cutting
• consider widening or designating additional protected areas to mitigate against pressures such as trampling by hill walkers

WETLANDS AND LAKES

Issue: important rivers such as the Glenelly, a salmonid river. Most rivers support populations of the UK Priority Species otter.

Actions:

• protect water quality of rivers through nutrient management and by reducing suspended sediments; prevent areas of peat cutting from introducing peat particles into the spawning and nursery beds of fish
• promote and encourage existing good farming practices such as outlined in the Countryside Management guidelines so that streams are not polluted by run-off from agricultural land or seepage from silage pits
• monitor effects of peat cutting and forestry activities on pH, nutrients and sediment load and deposition in rivers and lakes

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