Nexus approaches to foster sustainable resource use: relations between stocks and flows of materials, services, and practices

Societies use material and energy resources to build up, maintain and utilize long-lasting structures such as buildings, infrastructures or machinery, and in the process release huge amounts of wastes and emissions. While in 1900 less than a quarter of all material use served to build up new material stocks, this fraction is now ~60% globally. Nexus approaches provide useful heuristics for interdisciplinary analyses of (un)sustainable resource use and the potentials and limitations of societal agency for interventions. Such a nexus can be conceptualized between different resources (e.g. land, materials, energy, or water), between biophysical stocks and flows involved in social metabolism, and the services and contributions to human well-being they provide. The novel concept of a stock-flow-service nexus explicitly recognizes the diverse and potentially conflicting purposes of resource use (e.g. products, services), thereby enriching concepts of “eco-efficiency”. At the same time, its applicability is in some contexts reduced by its dependence on the valuation of services, which has been subject to controversy and debate. Focusing on relationships between stocks, flows and practices, e.g. linkages between the routines of everyday life and the consumption of resources such as materials and energy, the complementary approach of a “stock-flow-practice” nexus avoids some of these challenges. Building on prominent theories of practice, especially those that have gained traction in consumption research, it offers a new conceptual basis for engaging with human agency and its implications for resource use. Both nexus approaches emphasize the key role of patterns of material stocks (e.g., settlement patterns, transport or production infrastructures, machinery) in shaping the (un)sustainability of resource use and the importance of services- and practice-oriented efforts to reshape these patterns when aiming to tackle the present sustainability crisis. In this presentation, we discuss how these two complementary nexus approaches can serve as heuristic models for interdisciplinary sustainability research, sketch the different conceptual and empirical research directions each of these two approaches inspires, and reflect on their importance for conceptualizing agency.