COUNTRYSIDE COUNCIL FOR WALES
SITE OF SPECIAL SCIENTIFIC INTEREST: CITATION
ANGLESEY TYWYN ABERFFRAW
National Grid Reference: SH365690
Site Area: 363.5 ha
Tywyn Aberffraw is of biological and geomorphological interest. It is a large and intact calcareous dune system with dune ridges (both mobile and consolidated) damp slacks and dune grassland together with a shallow lake and its outflow stream.
Inland of the relatively mobile fore dunes, low-lying slacks occur between more stable dune ridges and at the landward end of the system, where Llyn Coron is also situated, there is an extensive tract of fixed-dune grassland. Most of the site is grazed by livestock and there is a range of different terrestrial vegetation communities, many of which are floristically rich. A number of rare and uncommon plant species are present, e.g. early sand-grass Mibora minima, and the damp calcareous slacks are particularly noted for their interesting bryophyte assemblages which include both northern e.g. Catascopium nigritum and Mediterranean e.g. Southbya tophacea floristic elements.
Llyn Coron is a base-rich lake with an interesting aquatic macrophyte community and several uncommon species, e.g. eight-stamened waterwort Elatine hydropiper and hairlike pondweed Potamogeton trichoides, are present as well as a diverse invertebrate fauna. The Afon Ffraw, flowing from the lake, is tidal in its lower reaches, and its flora includes a water crowfoot Ranunculus fluitans, which is extremely uncommon in North Wales.
Tywyn Aberffraw is an important site for coastal geomorphology. It comprises an area of blown sand and dunes occupying a confined valley site. Because of the physical constraints, there is little possibility of sand entering the bay from alongshore and the bounding cliffs supply little material to the beach. Tywyn Aberffraw offers an excellent opportunity for the study of beach and dune relationships in an area of restricted sediment supply, both from the beach and within the site. A further important feature is the relative isolation of individual grey parabolic dunes upon a sand plain, a landform assemblage that has few comparable equivalents in England and Wales.