The “Nexus” concept has gained increasing interest as a framework to support the analysis of interconnected challenges of resource security and environmental sustainability. It emphasizes the relevance of understanding and describing the interdependencies among various sectors, such as water, energy, food, and ecosystems, but not necessarily limited to those, recognizing that actions in one domain can propagate effects across others, often resulting in trade-offs or synergies that traditional siloed policies overlook. Although Nexus research has been characterized by considerable progress on conceptual aspects, translating theoretical insights into actionable solutions for policy and management remains challenging. In this framework, the present Research Topic aimed to contribute to Nexus research with a two fold objective: (i) proposing tools, methods, and approaches capable of guiding the description of the main Nexus dimensions and implications, thus supporting its operationalization, and (ii) discussing how those can contribute to finding and formulating solutions for Nexus management and optimization, ultimately supporting actionable decision-making across scales and contexts.

As far as the first objective is concerned, particular emphasis is given to the identification of suitable approaches for Nexus modeling. Maragkaki et al. and Lilli et al. suggest that hydrological modeling remains crucial in this regard, as it helps analyze the main dynamics that characterize the water sector, along with the related implications in the food sector (e.g., in irrigated systems) and on the state of ecosystems. However, increasing attention is also given to integrated, interdisciplinary, and participatory modeling efforts, which try to find a balance between the need to analyze the complexity of Nexus and the need to provide synthesis. The study by Malamataris et al. highlighted the relevance of stakeholder engagement in Nexus, proposing the use of “Learning & Action Alliances” as structured engagement processes. This is crucial to understanding the local context and facilitating the identification of the specific challenges and perspectives, as well as the divergent perspectives among stakeholders toward upscaling. A sequence of participatory activities, ranging from stakeholder identification to both individual interviews and participatory exercises such as workshops, focus groups, and seminars, is used not only for understanding the main Nexus challenges but also for identifying and prioritizing the measures to tackle those challenges. The authors propose an innovative combination of modeling tools for this purpose, which include a Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis; System Dynamics Modeling (SDM); Serious Games (SG); and the Political Economy Analysis (PEA). Although analyzing the complexity of Nexus systems is fundamental, efforts are needed to provide straightforward information in an aggregated form. For this reason, Taguta et al. proposed a geospatial web-based integrative analytical tool (named iWEF) to facilitate the integrated assessment of Nexus resources in support of resilience building and adaptation initiatives and strategies. The tool is based on the Analytic Hierarchy Process (AHP), a multi-criteria decision-making tool capable of establishing numerical correlations among Water–Energy–Food (WEF) Nexus indicators and key “pillars,” such as availability, productivity, accessibility, and sufficiency. In addition to providing an integrated overview of Nexus, the iWEF tool also provides spatiotemporal information that can guide policy- and decision-making processes. Indicators are also proposed by Sargentis et al. to understand the evolution of WEF Nexus resources over time (focusing on the example of agricultural activities in Korinthos, Greece), highlighting potential inequalities and understanding the evolution that occurred in the last century mainly due to technological advancements and resource availability. Particular emphasis is given by the authors to the analysis of implications related to the variable water availability and use, agricultural productivity, and energy efficiency throughout the years. Interestingly, although the technological evolution significantly supported agricultural activities, contributing to an increased productivity, the Nexus does not appear to be optimized primarily due to inefficient management of water and energy, primarily due to overpumping.

Regarding the latter objective, the Research Topic also aimed to provide insights on solutions that can be identified to optimize Nexus, which can be both engineering measures and Nature-based Solutions (NbS). Specifically, Ronen Eliraz et al. evaluated the role of physical water infrastructure in providing safe drinking water and its impact on food provision for rural communities in Tanzania. A comparison between communities with and without water-intervention projects demonstrates that proximity to water sources (i.e., water accessibility and availability) significantly enhances food security. The implementation of NbS has also been suggested as crucial to support sustainable Nexus management, particularly in agricultural systems. In this regard, Maragkaki et al. explored the role of NbS at the basin scale, demonstrating how the ecosystem services they provide can help deal with the main sectoral and cross-sectoral challenges, reconcile multiple resource objectives, and support resilience along with productive land uses. Similarly, the relevance of NbS, mainly agro-ecological practices, has been discussed by Lilli et al. with specific reference to avocado plantations in Greece and by Malamataris et al. with reference to agricultural areas both in Greece and in Italy. Both studies showed that NbS are crucial to optimizing resource allocation, ultimately enhancing sustainability outcomes in agricultural systems.

In summary, the articles in this Research Topic collectively show that shifting from conceptual frameworks to practical applications often requires a blend of methods—including hydrological modeling, indicators, integrated modeling, and participatory modeling—tailored to the specific resources and governance landscapes under study. No single approach can fully address the complexity of Nexus interactions. Rather, the value of complementary strategies that integrate evidence-based analysis, quantitative and qualitative modeling, and scientific and stakeholder knowledge is highlighted. Interdisciplinary and integrated approaches are increasingly recognized as vital pathways for informing resilient and equitable resource governance. Stakeholder engagement enriches the relevance and accuracy of Nexus assessments and helps understanding implications and trade-offs, ultimately strengthening the ownership and feasibility of the proposed solutions; in the end, it supports inclusive and just implementation that merits wide social consensus, which, in turn, safeguards the longevity and reproducibility of solutions.

By orienting future research toward decision-making processes and the identification of pathways for implementing Nexus, the Nexus community can contribute more directly to addressing global challenges such as water scarcity, food insecurity, energy production, and ecosystem degradation, enriching both theoretical and practical dimensions of sustainable resource management.