“…Stirling (2010) argues that a narrow focus on risk, which commonly informs many decisionmaking processes and often underpins IA processes in practice, inadequately considers incomplete knowledge and can therefore lead to decisions that ultimately prove to be poor. He recommends that attention be paid to more "neglected areas of uncertainty" (Stirling, 2010(Stirling, , p.1030 including ambiguity and ignorance (and this generic meaning for uncertainty, encompassing uncertainty, ambiguity and ignorance will be used in this paper); thus the focus of this paper will be on ambiguity, uncertainty and ignorance, and not on risk. In IA, uncertainty is a recognised problem (de Jongh, 1988;Geneletti et al, 2003;Liu et al, 2010), although ambiguity and ignorance have received much less attention (a simple illustration is based on the number of results returned by the Scopus database at the time of writing considering the search terms "impact assessment" AND "uncertainty" (1,551), "ambiguity" (31) and "ignorance" (18) respectively), except where uncertainty is used as more of an umbrella term where ambiguity and ignorance are not distinguished.…”