Sites of Special Scientific Interest (SSSIs) notified under the 1981 Wildlife and Countryside Act are the statutory basis for nature conservation in Great Britain (NCC 1989). However, notification of the sites does not by itself ensure that the geological or biological features for which the site has been notified are maintained in a favourable state. They may deteriorate through natural changes (scrubbing-up of heathland or a rock exposure) or through mismanagement (the planting of introduced conifers in an ancient broadleaf woodland or the use of artificial fertiliser on species-rich chalk grassland).