SACs are strictly protected sites designated under the EC Habitats Directive. Article 3 of the Habitats Directive requires the establishment of a European network of important high-quality conservation sites that will make a significant contribution to conserving the 189 habitat types and 788 species identified in Annexes I and II of the Directive. The listed habitat types and species are those considered to be most in need of conservation at a European level (excluding birds). Of the Annex I habitat types, 76 are believed to occur in the UK. Of the Annex II species, 43 are native to, and normally resident in, the UK.
Ashdown Forest was submitted to be classified in 2005 as an SAC in March 2001 and achieved that status. It was awarded this because it has one of the largest single continuous blocks of lowland heath in south-east England. The site supports important assemblages of beetles, dragonflies, damselflies and butterflies, including the nationally rare silver-studded blue Plebejus argus, and birds of European importance, such as European nightjar Caprimulgus europaeus, Dartford warbler Sylvia undata and Eurasian hobby Falco subbuteo.