The Methodological Evolution of the Water-Food-Energy Nexus Index in Agriculture: A Systematic Review

Abstract The Water-Food-Energy (WFE) nexus has become a central framework for addressing resource sustainability in agriculture, yet its operationalization increasingly relies on composite indices whose methodological foundations remain fragmented. This study presents the first systematic and critical review of the Water-Food-Energy Nexus Index (WFENI) applied in agricultural systems. Following a rigorous PRISMA-guided protocol, we analyzed 21 peer-reviewed studies to examine indicator selection, index construction, weighting schemes, and validation practices. The review reveals a clear methodological evolution from early resource-efficiency metrics toward expanded frameworks that integrate environmental, climate, and emission dimensions. While normalization approaches are largely standardized, substantial divergence exists in weighting and aggregation, marking a gradual shift from equal and expert-based weights toward data-driven and optimization-based methods. However, a critical “robustness gap” persists: the vast majority of studies lack formal sensitivity or uncertainty analysis, raising serious concerns about reliability. This review systematically maps these methodological trends and outlines a strategic agenda for future research, advocating for the institutionalization of robustness testing, dynamic modeling, and expanded system boundaries to enhance the rigor and policy relevance of agricultural sustainability assessments.