Water-Energy-Food-Ecosystem Nexus approach for holistic resource assessment in Sardinia region

The sustainable management of water, energy, food, and ecosystems sectors is fundamental for ensuring societal well-being, economic stability, and environmental integrity. Sardinia is a Mediterranean region with diverse socioeconomic and landscape conditions, currently facing escalating challenges in managing the intertwined system between Water, Energy, Food, and Ecosystems, shaped by climate variability and pressing sectoral demand, especially during the dry months. This research applies the Water-Energy-Food-Ecosystem (WEFE) Nexus approach to assess the resource interdependencies, trade-offs, and synergies across the seven hydrographic districts of the Sardinia region, with both qualitative and quantitative tools for the holistic assessment of the WEFE system. The qualitative assessment was complemented by Hoff WEF nexus analytical framework, and Causal Loop Diagram (CLD) to identify the sectoral challenges and capture the dynamic interactions between WEFE sectors. The qualitative tools shaped the structure and parameters of the quantitative (R-WEFE Nexus platform) tool enhancing their ability to reflect the real-world dynamics and interactions within WEFE sectors. The R-WEFE Nexus platform was validated to analyse the impacts of sectoral dynamics, socioeconomic and climate change projections, and strategic management policies on nexus performance. The validated system dynamic-based R-WEFE Nexus platform was applied to the seven (Coghinas-Mannu-Temo, Liscia, Posada-Cedrino, Tirso, Sud-Orientale, Sulcis and Flumendosa-Campidano) hydrographic districts of Sardinia region, to simulate integrated trends over the historical (1981-2014) and future (2015-2070) periods by considering the socioeconomic and climate change scenarios under SSP126 and SSP585. 

The findings show a critical decline in reservoir water levels, projected prevalent warning conditions of reservoir status indicators (0.15-0.3) in most of the hydrographic districts under SSP126 and SSP585, and often falling below emergency threshold (< 0.15) during the peak seasonal water demand. This heightened vulnerability is expected from the combined effect of escalating irrigation for agriculture and the substantial rise in water demand associated with heightened tourist influxes during the summer months. Water quality is expected to be further compromised by elevated nitrate concentration in surface water largely attributable to agricultural runoff, affecting aquatic ecosystems. The increasing energy demand, fostered by increasing demand and degraded resources, does withstand growing development potential in the Sardinia region for integration of renewable energy sources (Solar and Wind) as a key strategy for reducing reliance on imported fossil fuels and significantly reducing CO₂ emissions.

The study emphasized the critical need for cross-sectoral collaboration and integrated governance to effectively tackle resource management challenges. Such efforts are important for ensuring sustainable development, and ecosystem integrity and enhancing resilience to the impact of socio-economic pressure and climate change, paving the way for advancing resource efficiency and long-term sustainability.