Sand Dunes (.PDF 486Kb)

NATURAL HERITAGE
The sand dunes of Northern Ireland have developed
over the last 5,000 years and are largely derived from
glacial sediment reworked since then by the tides and
wind. Archaeological finds within the dunes have helped
to determine the relative age of the sand dune systems.
Pottery, flints and bone remains excavated from sites on
the Murlough Dunes have been identified as belonging to
Neolithic, Bronze Age and Early iron Age cultures. Carbon
dating of fossils found in the dunes on the south side of
the Bann Estuary in Co Londonderry gave an age of 3,300
years BC. These dunes also contain evidence of human
occupation from Neolithic to Medieval times.
DUNE FORMATION
Sand dunes are more than just piles of sand: they are also
a complex living system of plants and animals. The dune
structure depends on the development of successive
vegetation communities as well as the purely physical
forces of wind, water and sand.
THE SRAND LINE AND FORE-DUNES
High spring tides and winter storms deposit tidal litter
(eg seaweed and driftwood) along the top of the beach.
The lines of litter provide nutrients, moisture and shelter
for plants like common orache, sea beet, sea rocket and
sea sandwort. These plants form a barrier to wind-blown
particles and start the build-up of sand.
Higher up the beach, out of reach of all but the highest
tides, sand couch and lyme grass trap sand particles and
cause a pioneer zone of mobile fore-dunes to develop.
FIXED YELLOW DUNES
The accumulation of sand accelerates as the highly
specialised marram grass quickly becomes the main
stabilising agent. It can cope with the very dry conditions
and can grow up through a covering of wild-blown sand.
At this stage, the dunes are known as ‘yellow’ dunes
because they are areas of bare sand with a low organic
content. These developing dunes are deficient in water
and plant nutrients and are unstable.
Hardy plants which can survive in this hostile environment
include dune fescue, sand sedge, sea holly and sea
bindweed.
TYPICAL SAND DUNE SYSTEM
HAMMOCK
STABLE GREY DUNES
SAND DUNES
(2009)
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NH 009
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The new foredunes stop the sand from reaching the ridges
behind which gradually become more stable. Mosses
and lichens colonise the sand between marram tufts and
a raw soil starts to form, allowing more plants to become
established. As organic material becomes incorporated
into the soil, it turns from yellow to grey.
(table overleaf)
Winter Annuals Perennials Nitrogen Fixers
sand cats tail
mouse-ear
chickweed
SHRUB
SAND DUNES
DUNE FIELD
pyramidal
orchard
bird’-foot trefoil
bee orchid white clover
whitlow grass vipers bugloss rest harrow
lambs lettuce blue fleabane kidney vetch
early forget-me-not carline thistle
FORE DUNE
PIONEER DUNE
BEACH
SAND DUNES

MATURE REAR DUNES
The vegetation which develops on the rear dunes varies
depending on the amount of calcium present.
CALCIUM RICH SOILS
Small herbs white clover, hare’s foot, wild thyme,
Lady’s bedstraw, bird’s-foot trefoil,
cat’s ear, mouse-ear hawkweed,
violets, germander speedwell.
Orchids twayblade, pyramidal, common
spotted.
Grasses red fescue, sheep’s fescue, common
bent-grass, meadow grass.
The dunes at Magilligan are built from sands rich in shell
fragments and other calcareous materials and support
species-rich grasslands similar to those found on chalk and
limestone.
Mosses grow between the herbs and grasses to give a
complete ground cover.
The oldest dune ridges at Magilligan tend to show some
soil acidification because rain water eventually leaches out
the calcium salts.
CALCIUM pOOR SOILS
On dunes built up from silica sand, for example at
Murlough, an acidic soil develops as rain water soon
removes what little calcium is present. These dunes
support many plants typical of acid heathland.
Primroses and bluebells flower in spring before the
bracken emerges as only a few plants like twayblades can
tolerate its shade. Dense scrub areas of burnet rose, gorse
and blackthorn are also found.
The very acid conditions on the oldest dunes support a
heath vegetation of ling, bell heather, moss and lichen.
DUNE SLACKS
Underneath most dune systems is a permanent layer of
fresh water floating on top of a denser layer of sea water.
The dune system at Magilligan overlies a layer of
impermeable clays and silts which keeps the water table
high. The hollows between dune ridges may lie very close
to the water table and can flood in winter. These wet areas,
called SLACKS, support a distinctive flora:
The dune pools often support lesser spearwort, bottle
sedge, bogbean and marsh marigold.
Wet slacks do not occur at Murlough because these dunes
were built over shingle which allows water to drain away
easily.
Flowering herbs marsh pennywort, bog pimpernel,
field gentian, grass of parnassus,
meadowsweet, water mint, yellow
iris.
Orchids marsh helleborine, northern marsh
orchid.
Grasses sheep’s fescue, white bent, heath
grass.
Sedges glaucous, carnation, sand.
Non-flowering variegated horsetail, adder’s tongue
fern, mosses (form a thick layer in
wettest areas).
Shrubs creeping willow.
INTERTEBRATES
The rich variety of plants and nectar-bearing flowers like
birds-foot trefoil and wild thyme attract many butterflies
including the dark green fritillary, grayling, common blue,
meadow brown and ringlet.
The six-spot burnett, a red and black day flying moth,
prefers the seaward areas of the dunes where it feeds on
ragwort. This yellow flower is also food for the yellow and
black striped larvae of the cinnabar moth.
Other invertebrates such as bees, wasps, beetles, flies and
spiders are numerous on the dunes. Snails are common
on the calcareous sand at Magilligan, but are restricted to
a narrow coastal strip at Murlough because the soil is short
of calcium which snails require for their shells.
COMMON BLUE
BEE

BIRDS
The short dune vegetation attracts ground-nesting species
such as skylarks and meadow pipits. Areas of scrub, are
used as nesting sites by woodland species, like willow
warbler, chaffinch, blackbird, robin, dunnock and wren.
Kestrels and sparrowhawks hunt over the dunes by day for
small mammals and birds, while long-eared owls hunt at
night for mice and shrews.
Waders often use the dune sands as roosts between high
tides when their feeding grounds are submerged. Many
species also use the dunes and slacks as nesting sites, such
as ringed plover, oystercatchers, snip and dunlin.
MAMMALS
The mammals that live on sand dunes are mostly nocturnal
and can be difficult to see, but footprints and droppings
may advertise their presence. Stoats and foxes visit dunes
to hunt for wood mice, pygmy shrews and rabbits. Badgers
sometimes dig setts in the dunes, but they generally prefer
the cover provided by areas of scrub.
Rabbits were introduced to warrens on many sand dune
systems for their meat and pelts. They became numerous
until myxomatosis destroyed large numbers in the 1950s.
Today, numbers are gradually increasing as rabbits appear
to be building up immunity to this disease.
Common seals haul out on the sands furthest away from
visitor hotspots.
THREATS
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Excessive trampling, use of vehicles and rabbit burrows
can all break up vegetation and expose bare sand to
the wind.
Trees planted to stabilise sand have destroyed the
typical dune vegetation.
Drainage, water extraction and afforestation can lower
the fresh water table and cause species – rich slacks to
dry out.
Sand mining or coastal defence works can reduce the
amount of sand reaching the dunes. Eventually, the
dune system may disappear.
The siting of industries, housing and caravan parks on
dunes causes total habitat destruction. Golf courses
may reduce species variety, but the roughs can provide
a haven for many dune plants and animals.
MANAGEMENT
Sand dunes are special habitats that provide refuges for
many unique plants and animals. They are also important
as a first line of defence: they protect inland
areas from erosion and flooding, and prevent the
contamination of ground water and farmland by salt water.
If they are to continue to provide areas for the enjoyment
of wildlife, for passive recreation and to fulfil their coastal
defence function, we shall need to take great care to avoid
their destruction.
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Human impact on dunes can be reduced by fencing
off sensitive areas and by providing surfaced paths
between car parks and the beach.
Damaged areas of bare sand can be repaired by
planting marram grass and sand couch grass.
Grazing and mowing help to maintain species diversity
by keeping coarse grasses and tree seedlings under
control.
Invasive species like sea buckthorn, sycamore and Scots
pine can be controlled by uprooting, but progress is
often painfully slow.
When visiting sand dunes, keep to the proper paths
and the beach. Do not walk over the dunes or pull
plants because this can destroy the fragile surface
vegetation and allow erosion to start.
SAND DUNES TO VISIT
Murlough National Nature Reserve, on the A2 between
Newcastle and Dundrum, Co Down. Owned and managed
by the National Trust.
Magilligan Point National Nature Reserve, at the entrance to
Lough Foyle, Co Londonderry.
Portstewart Strand and dunes. Owned and managed by
the National Trust.
CHAFFINCH
STOAT

SAND DUNES
REFERENCES
The Coastline - Barnes, RSK. (1977).
Publisher: John Wiley and Sons, Chichester.
ISBN 0 471 994707.
Sand Dunes and their Management -
Doody, J P. (1985).
Publisher: Joint Nature Conservation Committee,
Peterborough. ISBN 0 86139 324 4.
Sand Dunes Inventory of Europe -
Doody, J P. (1991).
Publisher: Joint Nature Conservation Committee,
Peterborough. ISBN 1 873701 07 1.
The Conservation of Sand Dunes -
Nature Conservancy Council. (1986).
Publisher: Nature Conservancy Council, Peterborough.
ISBN 0 86139 1896.
A Guide to the Sand Dunes of Ireland -
Quigley, M B. (1991). Publisher: European Union for Dune
Conservation and Coastal Management, Dublin. ISBN 0
9517779 04.
Coast Dune Management Guide -
Ranwell, D S. (1986). Publisher: Institute of Terrestrial
Ecology, Huntingdon
Our aim is to protect, conserve and promote
the natural and built environment for the
benefit of present and future generations.
Northern Ireland Environment Agency
Klondyke Building
Cromac Avenue
Gasworks Business Park
Belfast BT7 2JA
T. 0845 302 0008
www.ni-environment.gov.uk