CHANGES IN THE EXTENT AND FRAGMENTATION OF HEATHLAND AND OTHER SEMINATURAL HABITATS BETWEEN 1920-22 AND 1987-88 IN THE LLYN PENINSULA, WALES, UK

Habitat modification is assessed over a period of 20th century agricultural expansion in the Llyn Peninsula, a coastal district on the western oceanic fringe of Britain. Habitat area data were derived from vegetation maps produced by surveys in 1920-22 and 1987-88. These are compared to assess the extent and nature of habitat change and degree of fragmentation. There was an over-all depletion of 3 629 ha (44%) of semi-natural habitat, mostly due to conversion to agricultural grassland in low-lying areas. The major reductions were in dry heathland (1500 ha, 51%) and especially in wet heathland (1 738 ha, 95%), and there were also declines in the areas of scrub, fen and sand dune habitats. There appear to have been temporary fluxes in some vegetation types, especially wet grassland and bracken, and local gains have also offset losses in deciduous woodland. In many cases, habitat erosion has been accompanied by diminution in patch size, and there were fewer large areas of seminatural habitat in the 1980s. Implications for nature conservation are discussed, and it is suggested that the larger surviving patches should be a focus for priority protection. Possibilities for habitat redevelopment are considered.