Author(s): Janez Susnik

Linked Author(s):

Keywords: Water-energy-food nexus; System dynamics; Causality; Development

Abstract: There is increasing interest in the water-energy-food (WEF) nexus and future trajectories considering global change, resource sustainability, and ecosystem functioning. Nexus studies show a number of shortcomings: not representing all sectors; specific studies that are not widely applicable; being large scale, losing fine detail; not representing feedbacks; using inconsistent approaches between sectors. Two examples are shown that start to tackle these issues. This work presents a global analysis of the WEF-GDP (Gross Domestic Product) system, integrating these four sectors into a single, coherent analysis and modelling approach, offering consistency where it has been previously lacking. A Monte-Carlo sampling approach is adopted to characterise global variability. A system dynamics modelling approach quantifies a previously qualitative description of the global WEF-GDP system. Seven GDP scenarios assess future trends to 2100. Correlative and causal analysis shows links of varying strength between the WEF-GDP sectors. For example, the GDP-electricity consumption sectors are very strongly correlated while food and electricity consumption are more weakly correlated. Causal analysis reveals that ‘correlation does not imply causation’, often the case in complex systems. There are noticeable asymmetries in causal relationships between sectors. Historical values of WEF and GDP are well recreated. Future scenarios were assessed using seven GDP growth scenarios to 2100. Water withdrawals are close to other values estimated using very different approaches, and results suggest that humanity is at risk of exceeding the ‘safe operating space’ for water withdrawal unless it can be decoupled from economic groth. Food production estimates are also close to other studies by 2050, while electricity consumption is overestimated. This work is a valuable early step in providing a quantitative modelling framework to the previously qualitative descriptions of the water-food-energy-economic system. Key issues for nexus research are: •modelling between sectors is often inconsistent, making comparison challenging and prohibiting wider analysis; •ecosystem services are rarely reflected in nexus assessments, presenting an opportunity; •relating assessments to broader planetary targets/indicators (SDGs) is in its infancy; •a multi-disciplinary approach, with diverse stakeholders, is essential; •policy-relevant messages must be forthcoming.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022461

Year: 2022