Biosffer Dyfi

Situated at the coast of south-central Wales in the estuary of the Dyfi River, this biosphere reserve is representative of salt marshes and estuarine systems in the west of the United Kingdom. The estuary forms one of the most important wildfowl and shorebird centers in Wales and also comprises a Ramsar site.

Cors Fochno has a large expanse of primary raised mire and contains a high number of invertebrate species, including some of national and international importance. Upstream along the Dyfi Valley are remnants of native oak woodland.

Designation Date: 1977
Administrative Authorities: Ceredigion, Gwynedd and Powys, Wales, UK
Surface area (terrestrial and marine): 81,883 ha
Core area(s): 10,880 ha (terrestrial: 3,094 ha; marine: 7,786 ha)
Buffer zone(s): 1,424 ha
Transition area(s): 69,579 ha (terrestrial: 68,079 ha; marine: 1,500 ha)

52°24'44"N - 52°47'55"N
Longitude: 3°31'50"W - 4°13'45"W
Midpoint: 52°36'24"N - 3°54'14"W

Human Activities

  • Pastoral farming and forestry;
  • Tourism and outdoor recreation;
  • Sustainable living and technology development;
  • Natural resource re-habilitation, management and monitoring;
  • Environmental education and interpretation;
  • Cultural development

Ecological Characteristics

  • Dyfi is a glaciated catchment of predominantly hill land with thin, acidic soils developed on lower Palaeozoic sedimentary strata;
  • Broadleaf woodlands, typically sessile oak or ash dominated, are a feature of the valley slopes and its many tributaries, although conifer plantations now dominate large areas;
  • The bryophyte, lichen and fern communities of the shady, damp valley woods are particularly notable, with large numbers of Atlantic species;
  • Several areas of upland moorland occur, comprising mixtures of acid grassland, blanket bog and dwarf shrub heath, often contiguous with larger upland areas and supporting important bird populations.
  • The Dyfi is a classic bar-built estuary, and one of the foremost examples of a drying, sandy, nutrient-poor estuary. Important populations of migratory fish, birds and otter occur along with extensive areas of saltmarsh (Atlantic salt meadow);
  • The spit dune system of Ynyslas is an actively accreting system with good representation of dune community succession including marram fore-dunes and humid dune slacks.
  • The estuarine raised mire of Cors fochno is one of the largest and best preserved active raised bogs in UK. It is a key site for climate-related research and supports important assemblages of lower plants, invertebrates and birds.

Protection Classifications


  • National Nature Reserve
  • Site of Special Scientific Interest
  • Part of Wester Ross National Scenic Area

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                                                                              Last update: April 2017

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