Household food waste poses a serious threat to planetary boundaries, particularly regarding water use, since it translates directly into unnecessary consumption of virtual water, contributing to freshwater depletion and threatening water security in water-scarce regions. This study examines how household socioeconomic factors differentially drive the water footprint embedded in food wasted, and how these impacts vary across food categories. To do so, we combine detailed data on food waste quantities of representative Spanish households for the period 2018–2022 with data on unitary water footprint of consumption, in order to calculate the volume of virtual water embedded in food discarded by households. We then employ a pooled regression approach to estimate the socioeconomic characteristics influencing it, analysing differences across food categories and testing how the impact of household characteristics varies by categories. Our results reveal that higher socioeconomic status and larger households significantly increase the water footprint of food waste, while the age of the main shopper and the presence of children are associated with a reduction. Moreover, our findings show that the water footprint of vegetables and other foods categories is more sensitive to socioeconomic status, while the water footprint of meat and dairy categories shows a stronger effect driven by age and household size. These insights offer policymakers valuable guidance for the design of tailored policies for specific groups to reduce the water usage, focusing not only on those products with a higher waste level, but also with a higher water footprint.

Household food waste poses a serious threat to planetary boundaries, particularly regarding water use, since it translates directly into unnecessary consumption of virtual water, contributing to freshwater depletion and threatening water security in water-scarce regions. This study examines how household socioeconomic factors differentially drive the water footprint embedded in food wasted, and how these impacts vary across food categories. To do so, we combine detailed data on food waste quantities of representative Spanish households for the period 2018–2022 with data on unitary water footprint of consumption, in order to calculate the volume of virtual water embedded in food discarded by households. We then employ a pooled regression approach to estimate the socioeconomic characteristics influencing it, analysing differences across food categories and testing how the impact of household characteristics varies by categories. Our results reveal that higher socioeconomic status and larger households significantly increase the water footprint of food waste, while the age of the main shopper and the presence of children are associated with a reduction. Moreover, our findings show that the water footprint of vegetables and other foods categories is more sensitive to socioeconomic status, while the water footprint of meat and dairy categories shows a stronger effect driven by age and household size. These insights offer policymakers valuable guidance for the design of tailored policies for specific groups to reduce the water usage, focusing not only on those products with a higher waste level, but also with a higher water footprint. | Este trabajo ha recibido apoyo financiero del proyecto TED2021-132836A-I00, financiado por MCIN/AEI/10.13039/501100011033 y por la Unión Europea NextGenerationEU/PRTR, así como del Departamento de Ciencia, Tecnología y Universidades del Gobierno de Aragón y del Fondo Europeo de Desarrollo Regional, con número de subvención S01_23 | Si

Complex feedback mechanisms and interdependencies exist among the water–energy–food–ecosystems (WEFE) nexus. In water-scarce regions, fluctuations in the supply or demand of any single subsystem can destabilize the others, with water shortages intensifying conflicts among food production, energy consumption, and ecological sustainability. Balancing the synergies and trade-offs within the WEFE system is therefore essential for achieving sustainable development. This study adopts the natural–social water cycle as the core process and develops a coupled simulation model of the WEFE (CSM-WEFE) system, integrating food production, ecological water replenishment, and energy consumption associated with water supply and use. Based on three performance indices—reliability, coupling coordination degree, and equilibrium—a coordinated sustainable development index (CSD) is constructed to quantify the performance of WEFE system under different scenarios. An integrated evaluation framework combining the CSM-WEFE and the CSD index is then proposed to assess the sustainability of WEFE systems. The framework is applied to the Beijing–Tianjin–Hebei (BTH) region, a representative water-scarce area in China. Results reveal that the current balance between water supply and socio-economic demand in the BTH region relies heavily on excessive groundwater extraction and the appropriation of ecological water resources. Pursuing food security goals further exacerbates groundwater overexploitation and ecological degradation, thereby undermining system coordination. In contrast, limiting groundwater use improves ecological conditions but increases regional water scarcity and reduces food self-sufficiency. Even with the full operation of the South-to-North Water Diversion Project (Middle Route), the region still experiences a 16.4% water shortage. By integrating the CSM-WEFE model with the CSD evaluation approach, the proposed framework not only provides a robust tool for assessing WEFE system sustainability but also offers practical guidance for alleviating water shortages, enhancing food security, and improving ecological health in water-scarce regions.

Complex feedback mechanisms and interdependencies exist among the water&ndash:energy&ndash:food&ndash:ecosystems (WEFE) nexus. In water-scarce regions, fluctuations in the supply or demand of any single subsystem can destabilize the others, with water shortages intensifying conflicts among food production, energy consumption, and ecological sustainability. Balancing the synergies and trade-offs within the WEFE system is therefore essential for achieving sustainable development. This study adopts the natural&ndash:social water cycle as the core process and develops a coupled simulation model of the WEFE (CSM-WEFE) system, integrating food production, ecological water replenishment, and energy consumption associated with water supply and use. Based on three performance indices&mdash:reliability, coupling coordination degree, and equilibrium&mdash:a coordinated sustainable development index (CSD) is constructed to quantify the performance of WEFE system under different scenarios. An integrated evaluation framework combining the CSM-WEFE and the CSD index is then proposed to assess the sustainability of WEFE systems. The framework is applied to the Beijing&ndash:Tianjin&ndash:Hebei (BTH) region, a representative water-scarce area in China. Results reveal that the current balance between water supply and socio-economic demand in the BTH region relies heavily on excessive groundwater extraction and the appropriation of ecological water resources. Pursuing food security goals further exacerbates groundwater overexploitation and ecological degradation, thereby undermining system coordination. In contrast, limiting groundwater use improves ecological conditions but increases regional water scarcity and reduces food self-sufficiency. Even with the full operation of the South-to-North Water Diversion Project (Middle Route), the region still experiences a 16.4% water shortage. By integrating the CSM-WEFE model with the CSD evaluation approach, the proposed framework not only provides a robust tool for assessing WEFE system sustainability but also offers practical guidance for alleviating water shortages, enhancing food security, and improving ecological health in water-scarce regions.

The exchange of food commodities significantly contributes to alleviating the strain on land used for agricultural production by linking areas rich in land with those facing resource limitations. This study employs the entropy weight–TOPSIS method to measure the water–land–food system, utilizes a two-way fixed-effects model to examine the impact of food import competition on the coordination of the water–land–food system, and applies a spatial Durbin model to explore the spatial spillover effects of this impact. The findings indicate the following: (1) The average coordination level of the WLF system in China stands at 0.317, showing considerable variability. The WLF system coordination in all regions of China initially decreased and then increased in the period studied, with the northeast region exhibiting the highest level of coordination. (2) The competitive effect of domestic and foreign food costs driven by food imports has a positive impact on the coordination of the WLF system. For every 100,000 hectares of land saved through the competition effect, the coordination of China’s WLF system increases by 0.002. However, once the saved land exceeds 1.5 million hectares, the impact of import competition on the importing country’s food market becomes excessive and starts to have a negative effect. (3) Split-sample regression revealed that the positive effect of food import competition on the coordination of the WLF system is stronger in the southern region compared to the northern region. Additionally, the increase in the competition effect has a more pronounced impact on the coordination of the WLF system in major food production areas than in non-major production areas. (4) Based on the results of the spatial econometric model, the increase in the competitive effect of food imports in a region not only increases the coordination of the WLF system within that region but also positively impacts the coordination of the system in neighboring regions. (5) The land use efficiency of food imports acts as a conduit for the impact of food import competition on the coordination of the WLF system.

The exchange of food commodities significantly contributes to alleviating the strain on land used for agricultural production by linking areas rich in land with those facing resource limitations. This study employs the entropy weight&ndash:TOPSIS method to measure the water&ndash:land&ndash:food system, utilizes a two-way fixed-effects model to examine the impact of food import competition on the coordination of the water&ndash:land&ndash:food system, and applies a spatial Durbin model to explore the spatial spillover effects of this impact. The findings indicate the following: (1) The average coordination level of the WLF system in China stands at 0.317, showing considerable variability. The WLF system coordination in all regions of China initially decreased and then increased in the period studied, with the northeast region exhibiting the highest level of coordination. (2) The competitive effect of domestic and foreign food costs driven by food imports has a positive impact on the coordination of the WLF system. For every 100,000 hectares of land saved through the competition effect, the coordination of China&rsquo:s WLF system increases by 0.002. However, once the saved land exceeds 1.5 million hectares, the impact of import competition on the importing country&rsquo:s food market becomes excessive and starts to have a negative effect. (3) Split-sample regression revealed that the positive effect of food import competition on the coordination of the WLF system is stronger in the southern region compared to the northern region. Additionally, the increase in the competition effect has a more pronounced impact on the coordination of the WLF system in major food production areas than in non-major production areas. (4) Based on the results of the spatial econometric model, the increase in the competitive effect of food imports in a region not only increases the coordination of the WLF system within that region but also positively impacts the coordination of the system in neighboring regions. (5) The land use efficiency of food imports acts as a conduit for the impact of food import competition on the coordination of the WLF system.