Different arguments, same conclusions: how is action against invasive alien species justified in the context of European policy?

The prevention and management of invasive alien species (IAS) has become a high priority in European environmental policy. At the same time, ways of evaluating IAS continue to be a topic of lively debate. In particular, it is far from clear how directly policy makers' value judgements are linked to the European (EU) policy against IAS. We examine the arguments used to support value judgements of both alien species and invasive alien species as well as the relation between these value judgements and the policy against IAS being developed at European level. Our study is based on 17 semi-structured interviews with experts from EU policy making and from the EU member states Austria, Belgium, Germany and Hungary. We found that our interviewees conceived of IAS in very different ways, expressed a variety of visions of biodiversity and ecosystem services, and adhered to widely different values expressed in their perceptions of IAS and the impacts of IAS. However, only some of these conceptualizations and value judgements are actually addressed in the rationale given in the preamble to the European IAS Regulation. Although value judgements about IAS differed, there was considerable agreement regarding the kind of action to be taken against them.