Why are there data missing about Areas/Sites of Special Scientific Interest in some of the critical level/load datasets for download?

Some of the conservation agencies have provided information to National Vegetation Classification level for A/SSSIs (England primarily) and some have not. Where this level of detail is not available, the broad habitat classification has been used. In some cases, several critical loads may apply to habitats within this broad classification and as such, APIS advises to seek site specific advice from the relevant authority (eg conservation agency or site manager).