Modelling the Water-Energy-Food-Ecosystem Nexus for integrated and sustainable resource management in Sardinia region

Water, energy, food, and ecosystem security serve as the main pillars of sustainable development, deeply linked in a way that shapes economic growth, human well-being and environmental balance. Sector-specific frameworks often neglect the intersectoral links resulting in fragmented solutions that lead to inefficiencies, unforeseen consequences and unsustainable outcomes that weaken the resilience of interdependent sectors. The compound uncertainty due to shift in climate extreme, socio-economic imbalance, and increasing resource demand intensified the issue related to the Water, Energy, Food and Ecosystem sectors. The integrated approach “nexus” provides the understanding of complex intersectoral systems, enhance the synergies and minimize trade-offs to optimise the efficiency of resources. The main aim of this thesis is to enhance sustainable resource management, particularly focusing on the WEFE Nexus under historical conditions and projected changes in climate. The thesis is divided into two parts to obtain these objectives, beginning with chapter 2 where a comprehensive assessment of the Water-Food (WF) Nexus in the Sardinia region is carried on. This objective was achieved by utilizing the Simulation of Evapotranspiration of Applied Water model integrated with GIS libraries (SIMETAW_GIS), i.e., the crop-water-soil balance model used to accurately estimate the crop water demand and quantify the yield losses due to water stress under historical and future projections. The modelling of crop water demand and the effect of water scarcity on crops delivers critical perceptions for the policymakers that can support the management of water resources and form the foundation for adaptation management strategies in the Sardinia region. Chapter 3 expands the WF Nexus to a more holistic Water-Energy-Food-Ecosystem Nexus analysis utilizing both qualitative and quantitative tools to understand and assess the complexity of the intertwined nature of WEFE systems with a special focus on seven hydrographic subbasins of Sardinia region. The qualitative tools Hoff WEF Nexus analytical framework and Causal Loop Diagram (CLD) were utilized to capture and explore the key linkages between water, energy, food, and ecosystem sectors. The novel quantitative tool R-WEFE Nexus platform was validated and coupled with climate change and socio-economic scenarios to investigate the nexus behaviour under various scenario conditions and policy frameworks. The policies were assessed against predefined thresholds to test the effective resource management and ensure the sustainability of sectoral strategies with sustainability goals. The study identifies favorable and unfavorable trajectories offering strategic recommendations for better nexus performance. These include adaptive strategies for enhancing water resource management, tourism management, sustainable land management, decarbonizing the economy by increasing the proportion of renewable energy, agriculture resilience, and ensuring ecosystem integrity. The multiple policies were tested in R-WEFE Nexus platform effectively addressing the compound uncertainty stemming from socio-economic shift and hydroclimate variability intensified by changes in climate conditions. The thesis provided valuable findings and recommendations, particularly focusing on the holistic WEFE sectors of Sardinia Island. The application of the SIMETAW_GIS model and R-WEFE Nexus platform effectively assessed the W-F Nexus and WEFE Nexus sectors respectively. Projected changes in socio-economic and climate change highlight the increasing uncertainty in the WEFE sectors.