This section covers the heath and bog habitats in Wales, all of which are considered to be under threat and listed in Annex I of the EC Habitats Directive. There tends to be a lot of overlap between the dominant species in these habitats, making the habitats potentially difficult to differentiate, particularly in transitional states. Furthermore, the substrate can be the key determinant between heaths and mires, with raised bogs and blanket bogs always found on deep peat, i.e. peat more than a metre deep.