The creation and characterisation of a bioclimatic classification for Britain and Ireland

The paper discusses the creation of a bioclimatic classification for Britain and Ireland, which aims to provide discrimination between areas of conservation importance. The work used the UKCIP98 baseline data, which was supplemented with additional climate data for Irish stations to define a 21 class classification based on a 10 km square grid. The hierarchical classification was based on 89 monthly climate variables and bioclimate indices, chosen to reflect limits to species distribution. The classes were characterised by relating their distributions to the area of protected sites contained within each class and to the presence/absence of selected Habitats Directive Annex 1* Priority Habitats. The principal components analysis undertaken prior to the classification shows that the principal bioclimatic variables that discriminate areas across Britain and Ireland are (in order of explanatory power) related to rainfall, mean temperature and growing season, wind speed and the drying power of the air. The classification shows good discrimination between the small, dissected classes of upland areas and the more contiguous classes of lowland Britain and Ireland. The number of classes in northern and upland areas appears to be a reflection of the diversity of habitats within these areas.