Understanding the impact of regime complexes on global governance calls for creative policy thinking. This introduction provides a new and more precise definition of the concept of regime complex. It also suggests specific tools to characterize regime complexes and analyze their impacts on global governance. The articles in this issue deepen the analytical understanding of complexes by examining concrete examples in various domains of global governance such as piracy, taxation, energy, food security, emissions reduction, carbon sinks, biosafety, and refugee governance. In addition to providing an in-depth description of a variety of different regime complexes, this issue is innovative on three accounts: (1) it presents complexes both as barriers and opportunities for global governance and gives explanations for these diverse outcomes; (2) it shows how a broad spectrum of actors is necessary for understanding the creation and evolution of complexes; and (3) it qualifies former claims to the effect that only powerful actors can impact regime complexes.

This research brings together studies of non-state actors (NSAs) in environmental negotiations, transnational networks, and institutional fragmentation, to shed light on the influence of NSAs on policy-making in regime complexes. It presents a new analytical framework with a series of deductive assumptions about the influence of “multi-forum” NSAs, as compared with “single forum” NSAs. Multi-forum NSAs cover several elements of a regime complex, and are thereby able to follow and potentially influence fragmented institutional processes. Focusing on two cases of fragmented environmental governance—forestry and access to genetic resources—the analysis provides a quantitative (statistics, network analysis) and qualitative (interviews) testing ground for the proposed framework. Because of their considerable material, organizational and ideational resources, and long-term engagement, multi-forum NSAs have greater access to the negotiations and may become central players. The strategies such NSAs adopt can further the integration of regime complexes when they undertake forum linking, or push towards further fragmentation when they undertake forum shopping or forum shifting.

This collection of essays brings together scholars from various disciplinary backgrounds, based on three continents, with different theoretical and methodological interests but all active on the topic of complex systems as applied to international relations. They investigate how complex systems have been and can be applied in practice and what differences it makes for the study of international affairs. Two important threads link all the contributions: (i) To which extent is this approach promising to understand global governance dynamics? (ii) How can this be implemented in practice?

Regime complexes are arrays of institutions with partially overlapping mandates and memberships. As tensions frequently arise among these institutions, there is a growing interest geared to finding strategies to reduce them. Insights from regime theory, science and technology studies, and social network analysis support the claim that "boundary organizations"—a type of organization until now overlooked in International Relations—can reduce tensions within regime complexes by generating credible, legitimate, and salient knowledge, provided that their internal networks balance multiple knowledge dimensions. Building on this argument, this article offers an ex ante assessment of the recently created International Platform on Biodiversity and Ecosystem Services (IPBES). Results from our network analysis of IPBES point to clear improvements compared with similar organizations, although major deficiencies remain. The contribution of this article is threefold. Methodologically, it introduces new conceptual and technical tools to assess the '"social representativeness" of international organizations. Theoretically, it supports the claim that international organizations are penetrated by transnational networks and, consequently, that the proliferation of institutions tends to reproduce structural imbalances. Normatively, it argues that a revision of nomination processes could improve the ability of boundary organizations to generate salient, credible, and legitimate knowledge. (Résumé d'auteur

This article looks at regime complexes from a state policymaking perspective. It develops a theoretical model in which regime complexes become denser over time while governmental policymaking becomes more coherent. Under this model, interactions between global regime complexes and national policymaking are twofold. On the one hand, greater policy coherence generates negotiated mandates asking for regime connections and complex density. On the other hand, regime-complex density creates more cohesive audiences, which increase incentives for national policy coherence. This co-adjustments model brings states into the discussion of institutional interactions and critically questions the desirability and feasibility of recent calls for joined-up government and whole-of-government approaches.