Oblique aerial photograph of dune system (J B Ratcliffe 1991)


What is ‘special’ about Newborough Warren - Ynys Llanddwyn SSSI?

Newborough Warren - Ynys Llanddwyn has 32 special features:

  1. Coastal landforms and the processes controlling beach and dune development.

  2. Precambrian rocks exposed in coastal cliffs, foreshore exposures and inland outcrops.

  3. Intertidal rocky shore communities and rock pools

  4. Intertidal sandflat and mudflat communities.

  5. Saltmarsh communities from the lower to the upper zones including glasswort (Salicornia spp).

  6. Strandline, foredune and mobile dune communities.

  7. Semi-fixed/fixed dune grassland communities.

  8. Dune slack / mire communities.

  9. Heathland and dune heath communities.

  10. Shore dock.

  11. Fir clubmoss,

  12. Yellow bird’s nest,

  13. Crowberry,

  14. Dune heleborine

  15. Welsh marsh orchid

  16. Narrow leaved marsh dandelion

  17. An assemblage of nationally rare and nationally scarce vascular plant species.

  18. Petalwort (a liverwort).

  19. Nail fungus.

  20. An assemblage of nationally rare and nationally scarce lower plants (mosses, liverworts, fungi).

  21. Baltic stonewort.

  22. An assemblage of nationally rare and nationally scarce stoneworts (large freshwater algae).

  23. Golden hair lichen.

  24. An assemblage of nationally rare and nationally scarce lichens.

  25. Medicinal leech.

  26. Sandhill rustic (a moth).

  27. A marine polychaete worm Ophelia bicornis.

  28. An assemblage of dune invertebrate species.

  29. An assemblage of amphibians including great crested newt.

  30. Over-wintering waders/wildfowl including pintail.

  31. A non-breeding population of raven

  32. Breeding cormorant.

As well as the features listed above, Newborough Warren - Ynys Llanddwyn has other habitats or earth science features that contribute to the special interest. These include woodland, scrub, lakes and pools. This mixture of habitats is important for much of the other wildlife such as chough and red squirrel, and these too are components of the special interest of the site. Unless specified below, management of this site should aim to look after these habitats and species as well as the listed features of interest

What do we want Newborough Warren Ynys - Llanddwyn to look like?

The Precambrian bedrock geology at Ynys Llanddwyn should continue to be one of the best localities in Great Britain for the study of rocks of this age by maintaining their current level and continuity of exposure.


Precambrian rocks are well-exposed on Llanddwyn Island, for example at Porth y Tŵr (above) and the famous pillow lavas (right) are particularly well exposed around Gwddw Llanddwyn.

The coastal landforms should demonstrate the natural processes of sediment transfer and deposition within the local coastal system. These geomorphological processes (which move sand and mud to create beaches, dunes, slacks and estuarine flats) also create the physical template upon which biological features develop. This will be achieved by minimizing activities or structures that would interrupt the natural movement of sediment, and that would directly or indirectly cause damage to the coastal landform assemblage.

The site should exhibit typical rocky shore, shingle, dune and estuarine communities, normally including mudflats and sandy foreshore, strandline, foredunes, mobile and fixed dunes, humid dune slacks and saltmarsh. These will vary in their proportion and location in response to naturally changing landforms. There should normally be a strandline with embryonic dunes at some location on the shore each summer, areas of mobile dune “blowout” and areas of newly formed wet slack to provide early successional phases of these habitats. Dune woodland and scrub, composed largely of native species, may be encouraged to develop on inland parts of the fixed dunes where forest soils have formed. Dune heath should be maintained and encouraged wherever it occurs.

The site should support viable populations of shore dock and petalwort along with other rare and uncommon native species (both plants and animals) typical of these habitats. Viable populations of great crested newt and medicinal leech should occur in numerous pools. The estuaries should contribute to the support of wintering populations of wildfowl and waders, particularly pintail, and there should be breeding populations of, notably, cormorant, lapwing and skylark. The dune woodland should support roosting ravens and, where compatible with other objectives, red squirrels.

This should be achieved through a holistic approach to management, which recognises that critical processes, such as sediment supply and deposition, groundwater movement, plant and animal dispersion, occur on a landscape scale.

What management is needed on Newborough Warren - Ynys Llanddwyn SSSI and why?

Although Newborough Warren Ynys Llanddwyn is an excellent place for wildlife and geology it will only remain so if the necessary management continues. CCW will work with you to ensure that this management is carried out.

What does this mean in practice?

There are many factors that could damage the special features at Newborough Warren - Ynys Llanddwyn if they are not properly managed. These are the ones we regard as most important:

Mineral specimen collecting: Mineral and specimen collecting is a major threat to the geological interest on Ynys Llanddwyn, and there should be a presumption against collecting geological specimens. Visiting geologists should not be allowed to use hammers on the island and, as many universities already have specimens/thin sections from the site, no specimens should be collected unless demonstrably for new research.

Erosion: Beaches and sand dune systems experience natural fluctuations of erosion and deposition and these, particularly the cyclical erosion and redevelopment of the frontal dunes, should be welcomed. Nothing should be done to significantly hinder this process. Structures such as groynes, slipways or other coastal defences, which impede natural sediment movement, should be resisted. The dune systems are becoming increasing stable with the development of soils on the vegetated areas. The consequent loss of mobile sand removes an important invertebrate habitat. In the absence of natural events that increase mobility management measures may be required to ensure that significant areas of bare sand are present on the dune system. Conifers planted on the mobile dunes should be removed (including where possible the root plates) to restore natural profiles. Whilst minor erosion by people can be beneficial in maintaining bare areas, concentrated erosion at entrances etc. is not able to redevelop naturally and may require appropriate intervention. The processes of wind scouring, accumulation of sand around marram grass and gradual movement of dunes create new dune slacks in their wake and provide important new habitat.

Natural erosion of the bedrock on Ynys Llanddwyn is slow and its effect on the site interest negligible. Natural movement of sand in the vicinity of the island, leading to the covering of rock, will be tolerated. Movement of sand by coastal processes may reveal new exposures around Gwddw Llanddwyn and further inland. Such new exposures will need to be mapped and may reveal fresh examples of minerals which are depleted elsewhere.

Tourism infrastructure: This site is visited by thousands of people each year who access the site across the dunes and along the beach. Close liaison between site managers should ensure that footpath maintenance and development of other tourist infrastructure does not impact adversely upon the site interest.

Afforestation: The conifer forest was planted to stabilise the dunes. The trees prevent natural sand movement and pine litter smothers most of the natural dune vegetation. The trees also intercept and transpire significant quantities of water, depleting the dune groundwater (see below). Part of the forest may need to be removed to restore the groundwater to dune slacks and the pattern of mobile and fixed dunes. Where distinct forest soils have developed there should be a presumption in favour of retaining native trees to establish semi-natural dune woodland.

Scrub:The development of scrub (blackthorn, willow, birch) on the dunes shades underlying dune vegetation, increases soil nutrients and the loss of groundwater. A limited area of scrub can be valuable for its associated fauna and its potential for development of woodland and copses, but should not be at the expense of more diverse dune vegetation. The invasive spread of sea buckthorn (not native to this area) should be resisted in particular.

Groundwater: Dune slacks indicate the groundwater-table at the time of formation (wind does not scour wet sand) and they should flood in normal winters to provide conditions necessary for species such as petalwort and other rarities. The forest (and drainage ditches associated with it) has caused lowered water levels across much of the site, leaving many slacks dry. Management of the forest to reduce interception and evapo-transpiration by conifers and infilling of drainage ditches are required to restore groundwater. The shore dock occupies water seepages from higher ground as well as the banks of pools and slacks where it appears to benefit from the minor disturbance associated with land-slips and light trampling

Grazing: Grazing on the dune grassland and slacks removes excess herbage and reduces competition from coarse grasses or scrub, allowing typical sand dune species to flourish. Grazing with (preferably) ponies or with cattle or sheep also enables rabbits to establish sustainable colonies (they cannot maintain a viable population in the absence of larger grazing animals) and create a patchwork of grazing patterns and sward height. The warm bare sand associated with hoofed animals and with rabbits is important for many invertebrates and their predators and creates opportunities for renewed dune movement.

The saltmarshes are mostly ungrazed by larger animals, having developed distinctive vegetation under that regime. Any grazing allowed on these areas should be very light and occasional if this vegetation is not to be altered.

Grazing animals within the forest and glades can reduce bramble thickets but should not be at a level which impedes native tree regeneration in the longer term.

The dung from grazing animals is an important resource for invertebrates (and thereby for insectivorous birds including chough) and for fungi. The use of parasite drenches should be avoided or minimised. Grazing stock also provide blood for medicinal leeches in some pools, apparently without significant harm to the host animals.

Soil nutrients: These dune soils are characterised by low levels of nutrients (N,P,K,) and high levels of calcium. Fertilisers, including atmospheric Nitrogen (NOx) pollution, encourage the growth of coarse grasses at the expense of the desired species. The use of any form of artificial fertiliser should therefore be avoided. Wind erosion and rabbit burrowing ensures that calcareous (shelly) sand is regularly brought to the surface to replace acid soil layers.

Cord grass: Common Cord-grass (which developed from the hybridisation of American and British precursors) colonises mudflats. However, it often exploits sedimentary changes within the estuary – in the case of the Cefni, the halving of the estuary size by the Malltraeth Cob and the canalisation of the Afon Cefni, which reduces tidal scour and permits the increased accumulation of sediment. Common Cord-grass will be succeeded by conventional saltmarsh vegetation. Its control is thus a short term and unsustainable action.

Wildfowling: There is no evidence that the levels of wildfowling occurring in Britain directly affect the populations of the quarry species. However, at a local scale the disturbance caused by shooting may deny feeding opportunities to wintering populations of waders and wildfowl at a critical stage in their survival. Controlled shooting occurs on Traeth Cefni (and Y Foryd) whilst Traeth Melynog is a sanctuary zone.

Disturbance: Nesting birds require undisturbed conditions. Beach recreation (particularly with dogs) threatens nesting ringed plover, boating threatens nesting cormorant. Codes of conduct and zoning of activities can alleviate some of these problems. Uncontrolled cockling remains a problem on the estuaries leading to disturbance of wintering birds.

Fishing activity: Bait collection and cockle collection are legitimate activities but poor practice can reduce the diversity of the communities and continued survival of the populations. Fishermen should follow codes of good practice such as infilling pits, putting boulders in their original position, avoiding areas of seagrass beds and returning undersized shellfish

Invasive Species: Several non-native species such as cotoneaster, montbretia and tor-grass threaten to smother areas of interest and may need to be controlled or eradicated. An alien seaweed, wireweed has also been recorded. Although currently not a problem, its presence should be monitored.


Our knowledge and understanding of wildlife is continually improving. It is possible that new issues may arise in the future, whilst other issues may disappear. This statement is written with the best information we have now, but may have to change in the future as our understanding improves, in particular, of the possible/probable impact of climate change. Any information you can provide on the wildlife of your site, its management and its conservation would be much appreciated.

If you would like to discuss any aspect of your SSSI, or have any concerns about your SSSI, please contact your local CCW office.

Your local office is:

Cyngor Cefn Gwlad Cymru

North Wales Region

Llys y Bont

Ffordd y Parc

Parc Menai



LL57 4BN

Telephone: 01248 672500

Fax: 01248 679259