An area of the Dyfi estuary was initially designated a biosphere site in 1977. After a period of local consultation, this area was extended by UNESCO in 2009. Today, an area of 81,883 hectares is included in the biosphere reserve. Of this, there is a core area of 10,880 hectares, a 1,424-hectare buffer zone and a 69,579-hectare transition zone, including terrestrial, freshwater and marine environments. This effectively covers the whole catchment of the Dyfi and its tributaries, and extends southward to include the university town of Aberystwyth. UNESCO defines its biospheres as reserves that ‘promote solutions reconciling the conservation of biodiversity with its sustainable use’. UNESCO’s website states that the reserves are ‘learning areas for sustainable development under diverse ecological, social and economic contexts, touching the lives of more than 250 million people’. There are currently 727 biosphere reserves in 131 countries, including 22 transboundary sites. Dyfi is the only biosphere reserve in Wales. Across the whole of the UK, there are another six: the Isle of Wight; the Isle of Mann; Brighton and Lewes Downs; North Devon; Galloway and Southern Ayreshire; North Devon and Wetser Ross. Four other sites, including the North Norfolk coast, were once biospheres but have had their designation withdrawn for failing to meet the necessary criteria.