ABSTRACT
Invasive alien species (IAS) were already described as a threat to biodiversity at the time the Habitats Directive was adopted, in May 1992. Various international treaties, amongst which the 1979 Bern1 and Bonn2 Conventions, but also the 1982 Montego Bay Convention,3 had previously stressed the need to address the impact of ‘non-native’ or ‘exotic’ species on indigenous fauna and fl ora. The issue was already mentioned in the Birds Directive.4 It was already high on the agenda of the IUCN.5 It was also on the negotiating programme of the Rio Convention on Biodiversity, leading to the adoption of a provision inviting Parties ‘as far as
those alien species which threaten ecosystems, habitats or species’.
