This chapter provides an integrative view of the sustainability challenges of urban systems. Thereby, urban metabolism is explored as a promising framework which is often praised as offering a systemic understanding of sustainability challenges in different areas. Nevertheless, this framework still has several shortcomings. To overcome these limitations and to better understand what the urban characteristics are that make cities (un)sustainable and contribute to global (un)sustainability, we take a historical perspective. This is combined with additional pieces of evidence into a general and systemic metabolic view of the effects of urbanisation on social, environmental, and economic sustainability. The chapter concludes by proposing an integrative and transdisciplinary framework to cover the multiple facets of urban sustainability both in terms of spatial scales and from a disciplinary point of view.

− ESG–Agency scholarship highlights the multiscalar and multilevel dynamics of earth system governance, with particular focus on the institutional and geographic scales.− Agents in earth system governance deploy diverse strategies and mechanisms, such as networks, bridging organisations, and orchestration, to navigate across global to local levels and ecological, social, economic, and political scales.− Whether multilevel and multiscalar dynamics enable or constrain agency in earth system governance depends on power dynamics and the resource capacities of agents.− Future research should examine the role of agents in political struggles related to the social construction of levels and scales in earth system governance.

− ESG–Agency scholarship highlights the fragmented, expanding, and complex forms of authority that prescribe, steer, and govern behaviour on environmental issues. − Agency scholarship on earth system governance covers interdisciplinary debates in four broad areas: the types of agents, the ways authority is exercised, the nature of agents’ influence, and the varieties of governance structures or architectures within which agents act.− Even with increasing scholarship into the fragmentation of authority and multiplication of the types agents to include nonstate, transnational, and subnational actors, states continue to be the centre of agency scholarship. Future research is needed on agency theory and the theoretical nature of relationships between actors and within differing geographic, economic, and political contexts.

− Allocation & Access in ESG–Agency studies is broadly seen as the process of sharing resources among multiple users, where efficiency and equity are the analytical tools for allocation and access, respectively.− Within ESG–Agency scholarship, the allocation of and access to water, food, land, and forest systems is studied widely, but is especially focused on developing countries in Asia, Africa, and South America.− Opportunities for future research include furthering understanding the trade-offs and synergies in conservation policies and potential conflicts with ownership and livelihoods, the role of gender in resource management (especially water resources), evaluating the types of power wielded in this area, and understanding how people acquire it.

− Agency is one of five core analytical problems in the Earth System Governance (ESG) Project’s research framework, which offers a unique approach to the study of environmental governance. − Agency in Earth System Governance draws lessons from ESG–Agency research through a systematic review of 322 peer-reviewed journal articles published between 2008 and 2016 and contained in the ESG–Agency Harvesting Database.− ESG–Agency research draws on diverse disciplinary perspectives with distinct clusters of scholars rooted in the fields of global environmental politics, policy studies, and socio-ecological systems. − Collectively, the chapters in Agency in Earth System Governance provide an accessible synthesis of some of the field’s major questions and debates and a state-of-the-art understanding of how diverse actors engage with and exercise authority in environmental governance.

− ESG-Agency scholarship on accountability is linked to legitimacy and agency theories and to research on architecture and power. − ESG-Agency scholars often consider accountability as an isolated, static and normative property, with relatively little critical reflection on its broader, evolving role in earth system governance. − Greater theoretical development is needed on how accountability operates between extremes of governance level (individual to international) and how this relates to international environmental governance initiatives.

− ESG-Agency scholarship most commonly focuses on the global arena as well as Asia and Europe, with critical geographic gaps in Africa and the Middle East.− Climate change is the dominant issue studied in ESG-Agency research, followed by forests and fresh water. − To address the geographic imbalance in ESG-Agency research, scholars need to develop research projects and collaborations in understudied regions while also recruiting and supporting scholars in those regions to engage with this research agenda.

− ESG-Agency scholars are at the forefront of exploring novel forms of agency within changing global governance architectures, such as the emergence of transnational and private governance, over the last decade. − Agency and architecture influence each other in a range of ways, underpinning processes of change in institutions, governance, and politics.− Greater focus is required concerning causal mechanisms of agency-architecture interplay, and their role in producing reflexivity and transformations in governance systems under pressure.

− ESG–Agency scholars focus on the question of how knowledge can be a source of authority for a diverse set of state and nonstate actors, allowing them to influence environmental decision-making. − Key themes in the literature on agency in earth system governance over the past decade include the knowledge-based agency of scientists and local or indigenous actors, learning, and the link between knowledge and power.− ESG–Agency scholarship contributes to larger debates in the social sciences concerning the growing importance of participatory processes of knowledge co-production, moving beyond the conventional primacy of scientific expertise in environmental governance and elevating the role of nonscientific knowledge holders.

− Norms are conceptualized in different ways by ESG–Agency scholars, including as regulatory instruments, as part of the surrounding structure, as the outcome of a legitimation procedure, or as an expectation of the researcher. − Actors who engage with norms exercise agency by shaping, strategically interpreting, and using, as well as managing other actors’ interpretations of norms.− Future research could benefit from more explicitly theorizing the interaction of agency and norms by integrating existing empirical insights and increasing the geographic diversity of scholarship.

− Over the last decade, ESG-Agency scholars have increased their use of social and system dynamic theories, participatory and actorness approaches in agency theories, and justice approaches within critical theories.− Qualitative and multiple qualitative methods are the most widely used approaches in research on agency in earth system governance, with very slowly growing methodological pluralism. − In the future, scholars in this field may benefit from the integration of cross-disciplinary and increasingly complex methods in an effort to foster linking of environmental sciences more broadly into environmental governance research.

− ESG–Agency scholars have identified 20 environmental governance functions performed by agents in earth system governance, with most scholarly attention focused on rule-making and regulation; convening and facilitating participation; and knowledge generation, provision, and sharing. − Forms of governance and multilevel/multiscalar dynamics serve as structural factors that that enable or constrain the performance of agency in earth system governance. − ESG–Agency scholarship over the past decade confirms that the state remains a key agent of earth system governance, despite expectations that the state’s role would diminish with the rise of nonstate actors and the reconfiguration of authority in world politics.