A regionalised computable general equilibrium model assesses water energy food ecosystems nexus trade offs under policy and climate shocks in Greece

Abstract Resource pressure and climate variability are intensifying trade-offs across the water-energy-food-ecosystems (WEFE) nexus in Mediterranean economies. This paper evaluates these interactions for Greece using a static, multi-sector computable general equilibrium model calibrated to a 2015 Social Accounting Matrix and regionalised to distinguish key crop activities in Karditsa from those in the rest of Greece. Water and energy enter production as intermediate inputs, domestic and imported goods are imperfect substitutes, and household welfare is measured with a benchmark Cobb-Douglas utility index. Seven scenarios are analysed: a water-tariff increase, water-tariff revenue recycling, tariff plus water scarcity, a fossil-energy import-price shock, a renewable-energy activity-tax reduction, a combined energy-transition scenario and a food-system import-price shock. The results show that water constraints dominate the nexus. A water tariff combined with a 10% water-supply constraint reduces water activity by 16.6%, Greek agricultural activity by 9.8%, household utility by 13.1% and the composite WEFE index by 5.3%. Fossil-energy price shocks generate moderate cost-push effects in water, food processing and chemical industries, whereas renewable-energy support produces small positive system-wide effects. Trade protection has mixed outcomes: import substitution supports selected upstream activities but contracts food processing, livestock and the overall nexus index. The selected Karditsa crop accounts appear less exposed than national agriculture in the calibrated regionalized SAM, but this should not be interpreted as evidence that Karditsa is hydrologically resilient to drought. The findings support integrated water-efficiency, renewable-energy and food-system policies rather than single-sector interventions with implications for the Sustainable Development Goals (SDGs) related to water security (SDG 6), food security and sustainable agriculture (SDG 2), clean energy (SDG 7), climate action (SDG 13) and ecosystem protection (SDG 15). By highlighting trade-offs across these objectives, the study demonstrates the relevance of a WEFE perspective for integrated sustainable-development policy.