They must be chosen from the sites of Community importance by the member states and designated SAC by an act assuring the conservation measures of the natural habitat.
This, in turn, is part of the Emerald network of Areas of Special Conservation Interest (ASCIs) under the Berne Convention.
The value of the proposed site is considered in relation to the whole national resource of each habitat type and of each species.
Firstly, assessment of the relative importance of sites containing examples of the individual habitat types.
The criteria used in Stage 2 are intended to be used to assess the sites at the level of the nine biogeographical regions and the EU as a whole.