Causal Loop Diagrams for bridging the gap between Water-Energy-Food-Ecosystem Nexus thinking and Nexus doing: Evidence from two case studies

• The security of natural resources requires the development of holistic approaches. • Nexus management focuses on the complex web of interconnections among resources. • Qualitative System Dynamics Modelling supports a better Nexus understanding. • Analyzing Causal Loop Diagrams helps to identify challenges and leverage points. • Stakeholder engagement helps to enrich knowledge and improving models. The concept of Nexus management is gaining increasing attention in the scientific community as it emphasizes the mutual interdependencies among different sectors (typically Water, Energy, Food and Ecosystems − WEFE), overcoming the ‘silo’ approach that usually characterizes the management of natural resources along with a rather water-centered perspective. Supporting a comprehensive understanding of the cross-sectoral interdependencies and influences among sectors is a cutting-edge research issue, specifically as far as the production of ‘actionable’ knowledge for policy makers is concerned. Despite its success, the actual implementation of the Nexus holistic approach is still hampered by several barriers. Starting from the analysis of those barriers, this work describes a methodological approach based on Qualitative System Dynamic Model (and specifically Causal Loop Diagram – CLD), capable of enabling the transition from Nexus thinking to Nexus doing. The methodological approach maps and describes the dynamic evolution of complex WEFE Nexus systems, and proposes an innovative ‘leverage analysis’ – based on graph theory measures – for identifying policy interventions capable of impacting system state and potential evolution. The proposed approach is highly participatory as stakeholders engagement is facilitated throughout the modelling process. Besides a description of the methodology, the present work provides also full details on the results of its implementation in two different case studies in Europe.