Ecological challenges are becoming more and more complex, as are their effects on nature and society and the actions to address them. Calls for a more sustainable development to address these challenges and to mitigate possible negative future impacts are not unproblematic, particularly due to the complexity, uncertainty, and long-term nature of possible consequences (Newig et al. 2008). Knowledge about the various impacts—be they ecological, economic, or social—policies might have is therefore pivotal. But the relationship between such knowledge and the myriad ways it may be used is particularly challenging. The example of policy impact assessment systems is a case in point. Recent years have seen an institutionalization of such systems for evaluating consequences of regulatory activities across the Organisation for Economic Co-operation and Development (OECD 2008) and the European Union (CEC 2002). It is argued that, by utilizing scientific and other evidence, impact assessment has the potential to deliver more sustainable policies and to address large-scale global challenges.