The reasons for designation are:
- to identify a site of special scientific interest;
- to ensure consultation; and
- to provide a basis for protection measures.
The 1981 Act made much greater provision for the protection of sites from the effects of changes in land management. Owners and occupiers must receive a formal SSSI notification specifying why the land is of special scientific interest and listing any operations likely to damage that special interest. Before carrying out any listed operation an owner or occupier must give written notice to Scottish Natural Heritage and can only proceed if:
- Scottish Natural Heritage has consented;
- the operation is undertaken in accordance with a management agreement; and - four months have expired since notice was given.
The four month statutory consultation period can be extended by agreement, but if this is not possible a Nature Conservation Order, made by the Secretary of State after consultation with Scottish Natural Heritage, may also be used to extend the consultation period while protecting the area against the proposed operation.
The reasons for selecting particular sites as SSSIs inevitably involve a degree of subjectivity about selecting sites. This is recognised in the legislation by the fact that Scottish Natural Heritage is required to exercise its 'opinion' in relation to the suitability of a site for notification. A key document in relation to biological sites was the Nature Conservation Review (2 vols, CUP 1977), which reviewed the overall wildlife resource of Great Britain as it was known at the time and identified key representative sites. The criteria for the selection of plant and animal sites were published as Guidelines for Selection of Biological SSSIs by the NCC in 1989, and the Guidelines for Selection of Biological SSSIs: non-vascular plants were published by the JNCC in 1992. Those for geological and geomorphological (earth science) sites will be published shortly.
For biological sites there are two main criteria:
- Best examples: the aim here is to ensure representative samples of the overall range of wildlife habitats by notifying the best examples of each type. Also taken into account is the aim of representing geographical variation within habitat types.
- Critical standard - which means that all sites of a particularly high standard should be notified, usually because they contain habitats of a particularly rare, unusual or complex nature, or which support particularly rare species.
For earth science sites, the main criterion for notification is based on national or international research value. A site may be representative of , or the best example of , a key stage in earth history.
In Scotland (but not in England or Wales), the Natural Heritage (Scotland) Act 1991 (Section 12) established an independent Advisory Committee on SSSIs. For new notifications, if an owner or occupier questions the scientific grounds and, following discussions with Scottish Natural Heritage, does not withdraw his objection, Scottish Natural Heritage is required to refer the matter to the Advisory Committee, and may not confirm notification without having considered their advice (although Scottish Natural Heritage is not legally bound to follow it).
For existing notifications, where an owner or occupier objected at the time of the original notification and believes that the scientific basis for notification no longer exists, Scottish Natural Heritage is required to refer the case to the Advisory Committee. Where no objection, has been made at the time of notification, an owner or , occupier can have similar representations referred to the Advisory Committee once ten years have elapsed from the date of the original notification.
Scottish Natural Heritage was also given 'balancing duties' in the exercise of its functions. Under Section 3(1) of the 1991 Act, it is required to take appropriate account of:
- actual or possible ecological and other environmental changes to the natural heritage of Scotland;
- the needs of agriculture, fisheries and forestry;
- the need for social and economic development in Scotland or any part of Scotland;
- the need to conserve sites and landscapes of archaeological or historical interest;
- the interests of owners and occupiers of land; and
- the interests of local communities.
In the context of SSSIs this means that SNH can reconsider the evaluation of the site to be sure that it does in fact warrant protection; but any changes (for instance to site boundaries or to the list of operations considered likely to damage the special interest of the site) can only be justified on scientific grounds. Scottish Natural Heritage still has an overriding mandatory duty to notify any sites where it is of the opinion that the area is of special scientific interest as specified by Section 28(1) of the 1981 Act.