Climate change is a critical challenge of modern society, affecting the natural and built environment on an unprecedented scale. Greenhouse gas (GHG) emissions, deforestation, overuse of fertilizers, and increasing urbanization are the main causes of global warming (Lamb et al., 2021) and the major factors contributing to changing weather patterns over extended periods. Extreme weather events (e.g., floods, droughts, and heat waves), biodiversity loss, forest fires, health risks, and desertification are among the most evident impacts of climate change, highlighting the urgent need for mitigation and adaptation measures to limit the resulting economic, social, and environmental costs. To this end, the effective and rational use of resources comprises a significant priority, as climate change creates new conditions under which various socioeconomic activities should be developed.

Water, energy, food, and ecosystems are highly affected by climate change which, in turn, creates new conditions as to their sustainable use for serving human needs. The so-called “nexus approach” is a promising exemplar for the integrated management of such vulnerable sectors that promotes systemic thinking and analysis of interactions among interconnected elements. Therefore, the Water-Energy-Food-Ecosystems (WEFE) nexus approach supports the efficient management of the water, energy, food, and ecosystems sectors under a holistic view that delves into complex interrelationships, synergies, and trade-offs. The WEFE nexus is a concrete system whose components are inextricably linked through direct and indirect interlinkages (Papadopoulou and Mellios, 2023). Exploring, identifying, quantifying, and modelling these interlinkages can improve resource management and support WEFE nexus governance by developing more sustainable and efficient policies.

WEFE Nexus – Interactions among sectors
Source: Papadopoulou and Mellios, 2023

Efficient resource use is also at the heart of the SDGs. The SDGs shed light on existing pressures, while their achievement depends heavily on the sustainable use of available resources. Like the sectors of the WEFE nexus, the SDGs are interconnected, and achieving one SDG impacts the achievement of other SDGs. A set of specific targets accompanies each SDG, and a corresponding indicator measures the performance of each target. A significant number of SDGs’ indicators involve WEFE nexus sectors as they refer to the sustainable management of water resources, the production of energy through multiple sources, the development of agricultural and food sectors as well as the health and viability of ecosystems. In this framework, the specialization of the proposed indicators to more specific WEFE nexus indicators may contribute to the assessment of SDGs’ accomplishment level and reveal critical issues that should be improved in order to further boost sustainability. The spatial scale of indicators and the relevant data used to calculate them should also be considered, as the SDGs’ progress and successful implementation require adaptation to local specificities. Moreover, specific indicators support the exploration of existing gaps and shortcomings, the assessment of policy coherence, the design of integrated policies, and the exploration of trade-offs that threaten the balance of the WEFE nexus.

A considerable number of researchers focus on defining WEFE nexus indicators, and much literature deals with WEFE nexus indicators and their linkage to the respective SDGs’ indicators. The development of an integrated WEFE nexus indicator that measures the overall health of the WEFE nexus is also addressed in many research articles. In addition, the proposed indicators often correspond to more than one SDG because they refer to more than one WEFE nexus sector. A first set of indicators addresses issues related to agricultural and food sectors. These indicators focus on the production of agri- food products, the area of crop yields (e.g., cereals) (Saladini et al., 2018), the footprint of fertilizers (e.g., nitrogen), the quality of agricultural products according to established food standards, and the extent to which farmers use modern technologies. Moving to the sector of water, indicators concern the reduction of water losses in agriculture (Papadopoulou et al., 2022), the limitation of irrigated crops (Papadopoulou et al., 2022), the elimination of toxic substances released in surface water and groundwater reservoirs (water quality indicators) (Vanham et al., 2019), the calculation of flood and drought risks, the calculation of treated water volumes (wastewater treatment), etc. Energy-related indicators place emphasis on GHG footprint, carbon footprint (Vanham et al., 2019), electricity generated from renewable energy sources (e.g., hydropower, solar, wind, biomass, agricultural waste), energy production per m³ of treated WW (Nika et al., 2022), the energy demand of different economic sectors (e.g., industry and agriculture), energy generated from fossil fuels, and the footprint of the transport sector. Finally, ecosystem indicators focus mainly on the calculation of ecological flow, ecosystem health, the ecological footprint (Vanham et al., 2019), the available forest land (Mabhaudhi et al., 2021), the rates of biodiversity loss, the endangered species, etc.

The design of WEFE nexus indicators constitutes one of the main research areas of several projects addressing nexus issues. It is a timely research topic as it serves WEFE nexus monitoring by shedding light on existing pressures and revealing potential future risks. It also contributes to the improvement of the WEFE nexus governance by supporting evidence-based decision making and thus setting the ground for the design of integrated and more coherent policies.

References

1. Lamb, W. F., Wiedmann, T., Pongratz, J., Andrew, R., Crippa, M., Olivier, J. G., Wiedenhofer, D., Mattioli, G., Al Khourdajie, A. and Minx, J., 2021. A review of trends and drivers of greenhouse gas emissions by sector from 1990 to 2018. Environmental Research Letters, 16(7), 073005, DOI: 10.1088/1748-9326/abee4e.
2. Mabhaudhi, T., Nhamo, L., Chibarabada, T. P., Mabaya, G., Mpandeli, S., Liphadzi, S., Senzanje, A., Naidoo, D., Modi, A. T. and Chivenge, P. P., 2021. Assessing progress towards Sustainable Development Goals through nexus planning. Water, 13(9), 1321, https://doi.org/10.3390/w13091321
3. Nika, C. E, Vasilaki, V., Renfrew D., Danishvar, M., Echchelh, A. and Katsou, E., 2022. Assessing circularity of multi-sectoral systems under the Water-Energy-Food-Ecosystems (WEFE) nexus. Water Research, 221, 118842, https://doi.org/10.1016/j.watres.2022.118842
4. Papadopoulou, C.-A. and Mellios, N.: Integrating Water-Energy-Food-Ecosystems (WEFE) Nexus Indicators and SDGs , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6277, https://doi.org/10.5194/egusphere-egu23-6277, 2023.
5. Papadopoulou, C.-A., Papadopoulou, M. and Laspidou, C. 2022. Implementing water-energy-land-food-climate nexus approach to achieve the Sustainable Development Goals in Greece: Indicators and policy recommendations. Sustainability, 14(7), 4100, https://doi.org/10.3390/su14074100.
6. Saladini, F., Betti, G., Ferragina, E.,Bouraoui, F., Cupertino, S., Canitano, G., Gigliotti, M., Autino, A., Pulselli, F. M., Riccaboni, A., Bidoglio, G. and Bastianoni, S., Linking the water-energy-food nexus and sustainable development indicators for the Mediterranean region. Ecological Indicators, 91, 689-697, https://doi.org/10.1016/j.ecolind.2018.04.035.
7. Vanham, D., Leip, A., Galli, A., Kastner, Th., Bruckner, M., Uwizeye, A., Van Dijk, K., Ercin, E., Dalin, C., Brandão, M., Bastianoni, S., Fang, K., Leach, A., Chapagain, A., Van der Velde, M., Sala, S., Pant, R.,  Mancini, L.,  Monforti-Ferrario, F., Carmona-Garcia, G., and Hoekstra, A. Y., 2019. Environmental footprint family to address local to planetary sustainability and deliver on the SDGs. Science of the Total Environment, 693, 133642, https://doi.org/10.1016/j.scitotenv.2019.133642