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Coastal Sand Dunes by dfsiopmhy6

VIEWS: 161 PAGES: 8

									                        Coastal Sand Dunes


Summary:

 UK BAP:
 Coastal Sand Dunes – Priority Habitat
 Current National Trend:
 Unknown
 Estimated Lincolnshire Resource:
 580 ha
 Progress towards BAP targets 2000 –2005:
    •	 Existing extent of sand dunes maintained.
    •	 Management of NNRs/SSSIs has resulted in favourable condition
        of habitat.
    •	 Humber SSSI extended.
    •	 Lincolnshire Coastal Audit published.
 Lead Partner:
 Lincolnshire Wildlife Trust


1. Introduction
Dunes form when there is an adequate supply of sand in the intertidal zone and where
onshore winds are prevalent. A sufficiently wide beach, the surface of which dries out
between high tides, is also important. Dry sand is then blown landwards and deposited
above the high water mark, where it is trapped by strand-line plants and dune-building
grasses such as sand couch Agropyron pungens, marram Ammophila arenaria and lyme
grass Leymus arenarius.

Several types of habitats make up dune systems. These are related to the time elapsed
since the sand was deposited, the degree of stability and the local hydrological conditions.
Along the storm tide wrack line a distinctive patchy strandline vegetation occurs, along
with a specialist group of invertebrates. The first obvious sand ridges are the mobile
dunes, immediately landward of the strandline, where sand deposition is greatest. They
support rather few plant species, the most characteristic being marram grass.

Semi-fixed dunes occur where the rate of sand deposition has slowed but there is still
a significant amount of bare sand. Fixed dune grassland forms when sand deposition
is no longer significant and the surface has stabilised and become fully vegetated, and
some soil development has taken place. Calcareous fixed dunes support a wide range
of plants, including orchids. Dune heaths, dominated by heather species, occur when
dunes have been acidified due to leaching of calcium or where the source sand is low in
shell or calcium carbonate. Dune slacks are wet depressions between dune ridges and
can include habitats such as marsh, pools and lagoons.




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Fixed dunes are, or have been, maintained by grazing, whether by stock or rabbits. In
the absence of grazing, they tend to develop into rough grass or scrub. Only one scrub
species, sea-buckthorn Hippophae rhamnoides, is confined to dunes, and it is native
to eastern England and south-east Scotland. It has, however, been widely introduced
elsewhere and can cause problems because of its invasive nature. As well as supporting
a wide range of species typical of upland grasslands and wetlands, coastal dunes provide
better conditions for warmth-loving invertebrates than any other UK habitat. Partly as a
consequence of this, some species occur further north in their distribution on the coast
than they do inland.

In the UK, major dune systems are widely distributed with a total of around 12,000 hectares
(ha) of sand dunes in England, 8,000 ha in Wales and around 33,000 ha in Scotland.
Fixed dunes and dune heath are particularly threatened habitats and are regarded as a
priority under the EU Habitats Directive.


2. Current Status in Lincolnshire
Sand dunes are a common feature on the Lincolnshire coastline,
especially between Cleethorpes and Mablethorpe in the north
and to the south of Skegness, towards the mouth of The
Wash. The middle section of the coast is a zone of erosion
now defended by large sea defence banks and sand dunes are
more fragmented here. However relict sand dunes can still be
found behind the sea walls. Some of these dunes (between
Sandilands and Chapel St Leonards) are important, but not
designated.

Seventy per cent of Lincolnshire’s sand dunes are in the Cleethorpes to Mablethorpe
stretch of coastline, where they form part of a complex of coastal habitats including
mudflats, saltmarsh, dune slacks and grassland. Good examples occur in the Saltfleetby-
Theddlethorpe National Nature Reserve (NNR) and at the Donna Nook NNR. Saltfleetby-
Theddlethorpe NNR is managed by English Nature in partnership with the Lincolnshire
Wildlife Trust (LWT). The dune system and its integral freshwater area are managed by
grazing, mowing and scrub control to maintain a wide range of habitat types, and old
ponds and dykes have been restored. Special attention has been given to maintaining
the natterjack toad Bufo calamita population. Within the NNR dunes there is an extensive
freshwater marsh, sometimes referred to as a ‘maritime fen’ because of the plant
communities found there.

The dunes at Donna Nook NNR, an LWT reserve owned by the Ministry of Defence, have
been enhanced by mowing and occasional grazing of dune grassland, the clearance of
some sea buckthorn, and the creation of a shallow lagoon.

North of Saltfleet Haven there is an area of now inactive, relict dunes dating back to the
14th century and there are also sand dunes on the Tetney Marshes Royal Society for the
Protection of Birds (RSPB) nature reserve. Although the extensive accretion along this
part of the coast is predominantly being consolidated as saltmarsh, new sand dunes are
being formed in places. Most of these dune formation sites on the north-east coast are
now protected by designations.

Between Mablethorpe and Skegness the dunes have been affected by coastal defence
works and other developments, especially tourism. The remaining dunes are small and
trapped on the landward side of the sea defence banks. However, they still retain a range
of characteristic dune wildlife.


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South from Skegness much of the sand dune area is within the Gibraltar Point NNR and
is also covered by Ramsar Site, Special Protection Area (SPA) and Special Area for
Conservation (SAC) designations. This is a zone of accretion where an extensive sand
dune system has been developing over several centuries, gradually extending southwards
in a series of parallel ridges running approximately north to south. Dune slacks here
are not as extensive as at Saltfleetby-Theddlethorpe, but the freshwater marsh with
natural and man-made ponds has a rich and varied plant and animal life. ‘Strip saltings’
(alternating strips of saltmarsh and low sand dunes) are well developed.

Much of the management at Gibraltar Point has been devoted to reconciling intensive use
for education and public enjoyment with the conservation of wildlife and natural features.
Habitat management and improvement has included the creation of a freshwater mere
and a brackish lagoon, and the control of scrub to maintain dune grassland areas grazed
by cattle and sheep.

Lincolnshire’s dune vegetation is not typical of Britain as a whole. While some national
vegetation communities, such as red fescue semi-fixed dune, are relatively scarce in the
county, sand couch grass mobile dunes are unusually common. Lincolnshire has over
26% of the national total of this habitat. Lincolnshire also has 55% of England’s sea-
buckthorn (perhaps most extensively found at Gibraltar Point and Saltfleetby NNRs). This
shrubby plant, which invades dunes, is nationally scarce and of European importance
and only occurs naturally along the east coast from the Humber to the Thames. It poses a
conservation dilemma; although it provides habitat for breeding birds and wintering birds,
it also is an aggressive coloniser of important dune grassland. A balance between the two
conservation objectives has to be maintained by active management.

Before the First World War, cattle and sheep grazed the dunes, preventing the spread of
buckthorn. The cessation of grazing, combined with a reduction in the rabbit population
through myxomatosis, has enabled sea-buckthorn to spread very quickly. This has
led to the loss of all or part of some botanically rich short grassland communities and
considerable changes in the structure of the dune vegetation. The buckthorn now has to
be carefully managed, bearing in mind its national scarcity, to maintain a diverse age and
class structure via rotational coppice blocks. However, foredunes exposed to tidal action
must be kept clear to allow the growth of low vegetation that will bind dune surface and
prevent tidal erosion.

There are also areas of seasonally wet grassland, freshwater marsh and maritime fen
within the sand dune complexes of Lincolnshire. These habitats are important for a
number of rare and scarce plant and animal species – including the natterjack toad.

The Saltfleetby freshwater marsh is particularly important for species of conservation
interest including two plants, the marsh pea Lathyrus hirsutus and marsh helleborine
Epipactis palustris, which are found nowhere else in the county. Some plants are at,
or near, their northern limit on the Lincolnshire coast. The sea bindweed Calystegia
soldanella, found on sand dunes, and the sea holly Eryngium maritimum, a plant of
shingle and the early stages of dune formation, are found near the northern limit of their
distribution at Cleethorpes. Both species also occur to the south at Gibraltar Point, this
is also the most northerly known site for sea heath Frankenia laevis, a nationally scarce
plant found in the sand dune-saltmarsh transition zone, the shrubby seablite Suaeda vera
and marsh-mallow Althea officinalis.




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Sand dunes are also good for invertebrates – Gibraltar Point and Saltfleetby-Theddlethorpe
are the richest coastal areas in Lincolnshire for invertebrates, and many of them are
rare or scarce nationally. A number of moths of conservation importance are found
in dune habitats in Lincolnshire. They include the marsh moth Athetis pallustris (a UK
BAP species), found at Saltfleetby-Theddlethorpe and Gibraltar Point, shore wainscot
moth Mythimna litoralis whose larvae feed on marram grass at Gibraltar Point, and the
micromoth Gelechia hippophaella, first recorded at Gibraltar Point, which feeds on shoots
of sea-buckthorn at Saltfleetby-Theddlethorpe.

Other invertebrates of interest include the crucifix beetle Panagaeus cruxmajor (a UK
BAP species), found in dune slacks at Saltfleetby-Theddlethorpe, one of only three known
sites in the UK, and the short-winged conehead Conocephalus dorsalis, a cricket found
at the northern limit of its range in Lincolnshire, where it occurs in damp places in dune
slacks at Donna Nook and Gibraltar Point.


3. Threats in Lincolnshire
   •	 Coastal squeeze due to rising sea levels.

   •	 Beach nourishment to restore sand beaches between Mablethorpe and
      Skegness. This has an impact on dune formation at Gibraltar Point. It is not clear
      exactly what effect this is having, but monitoring is being undertaken.

   •	 Inappropriate grazing levels. Continued grazing is necessary to maintain
      fixed dune communities, but over-grazing can have damaging effects. A more
      widespread problem is undergrazing, leading to invasion by coarse grasses
      and scrub. Although rabbits are effective in maintaining a short turf, grazing by
      livestock is needed to keep extensive areas under control.

   •	 Recreation is a major activity on dunes. Many dune systems are used extensively
      by holiday-makers, not only for walking but also for parking cars and in some cases
      for driving four-wheel drive vehicles or motorcycles. Excessive pedestrian use,
      e.g. between car parks and beaches, and vehicular use can cause local erosion.
      Dog walkers can also be a problem because dogs may disturb breeding birds and
      other wildlife. Major problems arise where there is widespread erosion of the turf
      year-on-year. Some dune systems are also used as golf courses. Although much
      original vegetation can be retained in the rough, the fairways, greens and tees are
      often highly modified by mowing, fertilising and re-seeding.

   •	 Natural but aggressive colonisation by sea-buckthorn reduces open species-
      rich sand dune communities. However, it is important to maintain a healthy
      population of this species, which is nationally scarce.

   •	 Falling water tables. Dune slack communities depend on a high winter water
      table. There may be considerable variation in the water table from year to year
      and specialised dune slack species are adapted to cope with this. However, a
      long-term fall in water table can lead to a loss of the typical dune slack plants and
      invasion by scrub and coarse vegetation. Causes of falling water tables include
      agriculture and housing developments.




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   •	 Sea defence and stabilisation. Many dune systems in Lincolnshire are affected
      by sea-defence works, or artificial stabilisation measures such as sand fencing or
      marram planting. These practices are more prevalent on developed coastlines
      where drifting sand may be perceived as a threat to urban or holiday developments,
      or where erosion is perceived as a threat to the sea defences. While careful dune
      management measures can help counteract severe erosion, engineered defence
      systems usually reduce biodiversity in dunes.

   •	 Dredging and marine aggregate extraction may also affect sand dunes through
      the disruption of coastal processes and removal of the sediment source.

   •	 Natural processes of dune erosion and formation. Unless artificially
      constrained, dunes can be highly mobile, although there is a natural trend towards
      greater stability with increased distance from the sea.
   •	 in the water table from year to year, which specialised dune slack species are


4. Progress towards BAP Targets 2000 – 2005
Targets:
   •	 Maintain the current area of sand dunes in Lincolnshire and (through appropriate
       management and protection) ensure their nature conservation interest is not
       lost.
   •	 Seek opportunities to restore areas of sand dune habitat lost to forestry, agriculture
       or other human uses.
   •	 Limit human interference to ensure the natural processes responsible for the
       formation and evolution of existing dune systems continue.

Management of existing sites has focused on maintaining the area and condition of the
habitat. Both Gibraltar Point and Saltfleetby-Theddlethorpe Dunes meet the criteria for
favourable condition under English Nature’s condition assessment.

Mowing, grazing and scrub clearance has occurred at Saltfleetby, Donna Nook and
Gibraltar Point NNRs along with other habitat enhancements.

Most of the important sites are designated as NNRs, Sites of Special Scientific Interest
(SSSIs) or Ramsar sites, or are included as part of SPAs and SACs. The Humber
SSSI has been extended and now includes more of the sand dunes on the north-east
Lincolnshire coast.

The Lincolnshire Coastal Audit – Towards a Strategic Approach on the Lincolnshire Coast
(LWT) was published in 2002. This survey of the coast between Tetney Sands in the
north and Gibraltar Point in the south identified coastal habitats including sand dunes.




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5. Objectives
   •	 To maintain existing dune systems by limiting human intervention to allow natural
      processes to continue.
   •	 To protect any currently undesignated sites from development.


6. Targets 2005 – 2015


Target 1      Establish a baseline for existing extent and condition of coastal
              sand dunes in Lincolnshire (including an assessment of habitat
              quality) by 2010.

Target 2      Maintain the current extent of sand dune in Lincolnshire (based on
              2010 figures) by 2015.

Target 3      Achieve favourable condition for all sand dunes by 2015.

Target 4      Expand the amount of sand dune habitat by adding a further
              100 ha by 2015.




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7. Actions required
               Also refer to Action Plans for Common Themes section
Action                                                        Date     Partners
Policy and Legislation
Ensure that measures to prevent disturbance and further       2010     LAs
loss of sand dune habitat to development are incorporated
into LDFs.
Designate all sites meeting Local Wildlife Site               2010     LAs, LERC,
guidelines.                                                            LWS panel,
                                                                       LWT
Develop coastal zone management policies which                2015     EA, LAs,
allow the maximum possible free movement of coastal                    WESG
sediment and pay full regard to the conservation of
sand dunes. Include dunes in Shoreline Management
Plans where they have a role to play in flood defence.
Managed realignment schemes should allow dunes to
migrate inland.
Site Safeguard and Management
Prepare detailed grazing, scrub control, vegetation           2010     NE, LAs,
restoration and visitor management plans for all dune                  LWT
sites.
Encourage golf course management policies and                Ongoing   NE, LWT
practices that are sympathetic to the flora and fauna of
sand dune systems.
Encourage the restoration of dune vegetation on dune          2015     NE, FWAG,
systems used for agriculture.                                          LWT
Support beach management strategies that encourage           Ongoing   NE, LAs,
protection of the seaward fronts of dune systems from                  LWT,
unsustainable pressure by pedestrian or vehicular traffic,
and discourage the use of mechanical beach cleaning
close to dune fronts.
Research and Monitoring
Identify existing areas of sand dunes on the coast and        2010     NE, LAs,
assess the wildlife value of the habitat through survey                LERC, LWT
and desk study.
Identify, assess and prioritise sand dunes where              2011     NE, LAs,
restoration of degraded or over-stabilised dunes is                    LWT
possible to reverse past losses, or landward migration of
dunes might be possible.
Monitor effects of beach nourishment between                 Ongoing   EA,
Mablethorpe and Skegness and also at Gibraltar Point                   LWT, NE,
NNR.                                                                   WESG
Advisory
Encourage the appropriate management and restoration         Ongoing   NE, FWAG,
of sand dunes by preparing and disseminating updated                   LWT,
guidance material to landowners and managers.                          WESG




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8. References
Houston J (1997) Conservation management practice on British dune systems, British
Wildlife, Volume 8: 297-307.

Radley GP (1994) Sand dune vegetation survey of Great Britain: a national inventory.
Part 1: England, JNCC, Peterborough.

Redshaw E J (ed.) (2002) Lincolnshire Coastal Audit – toward a strategic approach
on the Lincolnshire Coast, Lincolnshire Wildlife Trust.

UK Biodiversity Group (1999) Tranche 2 Action Plans. Volume 5 – maritime species
and habitats, English Nature, Peterborough


Revised 2006
A Simpkin (Lincolnshire BAP), N Pike (NE)




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