| Tayside Biodiversity - Tayside
Biodiversity Action Plan - Coastal - Sand Dunes |
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NATURE CONSERVATION IMPORTANCE
Dune systems generally comprise several distinct features:
FOREDUNES. These
are the youngest actively building dunes – often the most attractive for
recreation, but also the most susceptible to erosion. A few well-adapted plants
grow here such as Marram Ammophilia arenaria and Lyme-grass Leymus arenarius.
Many invertebrate species utilise the warm varied habitat provided by these dunes,
especially spiders, butterflies, hoverflies and moths.
YELLOW (SEMI-FIXED) DUNES.
Species such as Sand sedge Carex arenaria, Hawkweed Hieracium spp., Creeping
thistle Cirsium arvense, Rush-leaved fescue Festuca arenaria, Sea holly Eryngium
maritimum and Sea bindweed Calystegia soldanella begin to colonise the dry sand
between grass clumps, thereby progressively stabilising the dunes.
FIXED DUNES.
Dune grassland occurs as a more stable dune develops. Sand trapping plants give
way to sand “fixing” plants such as mosses and lichens (often Cladonia
lichens) which raise the humus content of the soil, creating a carpet through
which sand is unable to escape. Sand sedge forms a loose turf, accompanied by
species like Wild thyme Thymus praecox, Sand fescue Festuca rubra L. subsp arenaria,
and Birdsfoot trefoil Lotus corniculatus. Click beetles
may occur.
LANDWARD DUNE EDGE.
Where dunes are fairly stable ranker grasses and scrub species might seed in,
shading out some of the more interesting low-growing vegetation. Some invaders,
such as Sea buckthorn Hippophae rhamnoides leave an enriched soil which changes
the nature of the vegetation. Where grazing predominates, grassland may persist – otherwise
scrub or
woodland is typical. Where the soil is acid, heather dominated heath may develop.
Willow or birch dominates scrub on wetter dune slack areas.
DUNE SLACKS.
These are low-lying wetland areas between dune ridges. Dragonflies and damselflies,
as well as molluscs are found. Succession is largely determined by whether the
soil remains waterlogged and becomes increasingly acidic where rushes and bog
moss can dominate. If the soil dries out seasonally shrubs like Creeping willow
Salix repens may occur which provide a useful source of nectar and a foodplant
for invertebrates. |
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Mammals
Small mammals include several species of voles (Bank and Common), mice and Rabbits
Oryctolagus cuniculus whose grazing is important in maintaining the varied
vegetation structure and consequently the diverse range of habitats for plants
and other animals. Small mammals and shore-nesting birds attract predators
such as Foxes Vulpes vulpes, Weasels Mustela nevalis and Stoats Mustela erminea.
Roe deer Capreolus capreolus have also been seen, as have Brown hares Lepus
europaeus. Sheep graze the dune grassland at Barry Links.
Birds
Shore-nesting birds include Terns and Shelduck Tadorna tadorna. In the summer
Skylarks Alauda arvenis, Meadow pipits Anthus pratensis, Linnets Carduelis cannabina
and Stonechats Saxicola torquata are abundant. Birds of prey (including Short-eared
owl Asio flammeus and Merlin Falco columbarius) hunt the dunes and slacks, whilst
passage birds - including Fieldfares Turdus pilaris and Redwings Turdis iliacus
- winter among Sea buckthorn where they feed on the berries. On fixed dunes and
dune heaths and grasslands, species such as Skylark and Meadow pipit are typical.
Barry Links and Monifieth Bay SSSI both support nationally and internationally
important populations of wildfowl and waders and this is recognised by their
designation as part of the Inner Tay and Eden Estuary Special Protection Areas
(SPA) under the European Birds Directive.
Amphibians and Reptiles
Common toad Bufo bufo, Adder Vipera berus and Common lizard Lacerta vivipara
often favour the warm, dry and open sandy habitats provided by the dunes.
Invertebrates
The variety of coastal dune habitats supports a variety of invertebrates, including
grasshoppers, earwigs, many beetles, butterflies and moths. Sand-burrowing hunting
wasps and bees may be abundant on open dunes, with bumblebees inhabiting older
dunes. Crane fly grubs destroy marram grass shoots. Wolf and jumping spiders
occur. Dragonflies, mayflies and caddis flies live in the wetter slacks. Pond
skaters, water boatmen and whirligig beetles remain in or on the water. The Common
banded snail Cepaea nemoralis and Garden snail Helix aspera are also frequently
found. Small
pearl-bordered fritillaries Boloria selene are often seen. |
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Small blue butterfly
The Small blue, the smallest of Britain’s butterflies
(with a wingspan of
just 16 - 25 mm), has been in decline in the UK since the 1950s.
The
males have distinctive smoky-black wings with a silvery blue
dusting of
scales which they keep half-open to the sun during the breeding
season.
Breeding occurs where plant cover is sparse and the soil crumbly
and
fine, making the more sheltered sand dunes along the Angus
coast where
its sole foodplant the Kidney vetch grows, a favoured habitat.
Colonies are typically small and up to 30 adults will gather
to roost at
night on tall vegetation. Females lay eggs on the Kidney vetch
flowers
where the resulting grey-pink caterpillars later burrow into
the buds and
eat the developing anthers and seeds. By the end of July they
begin
hibernation within a crevice under soil or moss.
The following
spring
they seek a pupation site and the butterflies emerge from mid-May;
only
a few survive into the summer. |
Higher
plants
The rarest plant known from the
sand dunes of the Angus coast is Greater yellow rattle Rhinanthus
angustifolius found at Easthaven; it grows nowhere else in Scotland.
The Sea pea Lathyrus japonicus has also occurred in a few locations,
but in recent years only small numbers have been found at the
mouth of the Barry Burn. |
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Greater yellow rattle
Easthaven is the only location in Scotland for the Greater yellow rattle. It
is an annual plant best seen in July and August. It is hemi-parasitic and gains
its food partly from other plants.
Bees and posibly butterflies pollinate the flowers throughout the summer.
At Easthaven it grows mainly within tall open vegetation on the dune grassland.
SNH is currently
undertaking research to improve knowledge of this species and to ensure its future
management is
safeguarded. |
NATIONAL
BIODIVERSITY CONTEXT
There is a UK Broad Habitat Statement for sand dune habitat, which has the following
main objective:
Maintain the extent and enhance the habitat quality of sand
dune systems, and ensure the natural processes that create
them are not unduly prevented by human influence.
Measures to be considered further include:
Protecting sand dune habitats of conservation importance
from inappropriate uses.
Implementing strategies for managing the coastal zone at a local, as well as
regional and national level.
Reviewing the powers and duties of coastal authorities for safeguarding this
habitat.
Reducing the impact of sea level rise (and the resulting increase in wave attack
and dune erosion), including replacing unavoidable losses.
Reducing the damage resulting from the introduction of non-native species.
Encouraging appropriate levels of grazing on sand dune systems.
ECOLOGY AND MANAGEMENT
Much survey work has already been carried out on the designated
sites.
A full survey of the habitat is required in order to set up effective, area-wide
monitoring and assessment in the future.
Site Condition Monitoring of Sites of Special Scientific Interest is carried
out according to a 6 year programme.
CURRENT FACTORS CAUSING
LOSS OR DECLINE
Erosion
Unless artificially constrained seaward dune edges can be
highly mobile. Few dune systems are in overall equilibrium
and generally the coast of Tayside demonstrates net erosion.
Limited natural erosion helps regenerate dune systems, but
the survival of the biological interest and the actual structure
may be at risk if it increases excessively.
Recreation
The coast
and its sand dune systems offers easy access by local residents
and visitors and provides
opportunities to watch wildlife, pursue outdoor sports such
as golf, or simply walk, contemplate and seek
inspiration. However, such a major land use causes damage to
vegetation, exposes the underlying sand to the
wind and rain and results in the loss of vegetation and sand.
Rehabilitation of such areas can be carried out,
but it often takes years for the natural diversity to become re-established.
Grazing
Whilst continued grazing is necessary to maintain the grassland
and to prevent scrub development, overgrazing can have damaging
effects. Undergrazing is more widespread, allowing vegetation
to be invaded by coarse grasses and scrub.
Development
Pressure, especially
on the older dune systems, continues with further developments
proposed leading to the destruction of this habitat. Many
dune links are now golf courses where fertilisers, herbicides
and irrigation are used for ‘improving’ the vegetation.
Car and caravan parks widen access and increase trampling,
fires and disturbance.
Sea defences
Many dune systems are affected by coastal
defence works that arrest the formation of new dune systems and
affect the dynamism of dune systems.
Non-native species
Whilst the invasive Sea buckthorn scrub
stabilises the dunes at Barry Links, it also alters the dunes’ nutrient
status.
Afforestation
Over the years afforestation, often with non-native pines, has
restricted dune development causing changes in dune vegetation
and lowering water levels. Felling and permanent removal of trees
means that native vegetation can be restored in a relatively
short time.
Natural changes
Sea level rise and increased storms forecast as global climates
change may cause foreshore steepening, thus allowing increased
wave attack at the base of the dunes. |
MAIN
THREATS TO KEY SPECIES
| Sea pea |
- Lack of ground disturbance
on the dunes on which it grows.
Its remaining population at Carnoustie, Barry Burn, is “squeezed” between
the golf course and the dune edge. |
| UK importance
of Tayside population: |
high |
Greater yellow
rattle |
- Lack of habitat management
and potential erosion of the dunes on which it grows. |
| UK importance of Tayside population: |
high – globally threatened: this
is the only population in Scotland |
| Little tern |
- Disturbance and erosion
of nesting sites.
- Habitat loss due to development. |
| UK importance of Tayside population: |
moderate |
| Skylark |
- Loss of grassland habitat.
- Disturbance.
- Reduction in abundance of insect food. |
| UK importance of Tayside population: |
unknown - this is a UK Flagship Species
and in decline nationally. |
Small blue
butterfly |
- Loss of its foodplant,
the Kidney vetch. |
| UK importance of Tayside population: |
unknown - this species is in decline
nationally |
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