Risk governance denotes both the institutional structure and the policy process that guide and restrain collective activities of a group, society or international community to regulate, reduce or control risk problems. Risk governance has shifted from traditional state-centric approaches with hierarchically organized governmental agencies as the dominant locus of power to multi-level systems, in which the political authority for handling risk problems is distributed to distinct public bodies with overlapping jurisdictions that do not match the traditional hierarchical order (cf. Skelcher 2005; Hooghe and Marks, 2003). This implicates an increasingly multilayered and diversified socio-political landscape in which a multitude of actors, their perceptions and evaluations draw on a diversity of knowledge and evidence claims, value commitments and political interests in order to influence processes of risk analysis, decision-making and risk management (Jasanoff, 2004). Institutional diversity can offer considerable advantages when complex, uncertain and ambiguous risk problems such as social unrest need to be addressed because, first, risk problems with different scopes can be managed at different levels, second, an inherent degree of overlap and redundancy makes non-hierarchical adaptive and integrative risk governance systems more resilient and therefore less vulnerable, and third, the larger number of actors facilitates experimentation and learning (Renn, 2008). Disadvantages refer to the possible co-modification of risk; the fragmentation of the risk governance process; costly collective risk decision-making; and the potential loss of democratic accountability (Charnley, 2000).