This article introduces a special issue on the expanding research agenda on institutional fragmentation. The term refers to the growing diversity and challenges to coordination among private and public norms, treaties, and organizations that address a given issue area of international politics. International relations scholars increasingly address this phenomenon, framing it with alternative concepts like regime complexes or polycentricity. A considerable part of the existing debate remains focused on whether a centralized or polycentric governance architecture is preferable. Instead, as this special issue shows, domains of global environmental governance—like climate change, biological diversity, renewable energy, and forestry—are already fragmented. It is time to address new, more pertinent questions and help advance institutionalist research on this phenomenon. We introduce four major research themes for analyzing the fragmentation of different domains of global environmental governance: taking stock, causes, consequences, and responses.

Most research on global governance has focused either on theoretical accounts of the overall phenomenon or on empirical studies of distinct institutions that serve to solve particular governance challenges. In this article we analyze instead “governance architectures,” defined as the overarching system of public and private institutions, principles, norms, regulations, decision-making procedures and organizations that are valid or active in a given issue area of world politics. We focus on one aspect that is turning into a major source of concern for scholars and policy-makers alike: the “fragmentation” of governance architectures in important policy domains. The article offers a typology of different degrees of fragmentation, which we describe as synergistic, cooperative, and conflictive fragmentation. We then systematically assess alternative hypotheses over the relative advantages and disadvantages of different degrees of fragmentation. We argue that moderate degrees of fragmentation may entail both significant costs and benefits, while higher degrees of fragmentation are likely to decrease the overall performance of a governance architecture. The article concludes with policy options on how high degrees of fragmentation could be reduced. Fragmentation is prevalent in particular in the current governance of climate change, which we have hence chosen as illustration for our discussion.