Depletion of natural resources needs quantification and efficiency analysis of the use of resources to improve sustainability. This paper evaluates the efficiency of Organization for Economic Co-Operation and Development (OECD) countries in terms of Water-Energy-Land-Food (WELF-Nexus) to ensure sustainability and environmental viability for both present and future generations. An input-output index system is built at a transnational level. Composite and intrinsic indicators are introduced to incorporate the interconnections and tradeoffs between sectors of the nexus and outcomes of the nexus. The nonparametric benchmarking order-α model, resulting from Data Envelopment Analysis (DEA) is used to estimate WELF-Nexus efficiency of each country, and to alleviate the intricacies of using composite and intrinsic indicators. To ensure resource generativity, an output target setting model that accommodates predefined input is proposed. Results show variation in performance among OECD members, with an annual average efficiency score of 68%, 69% and 78% in 2007, 2012, and 2016. Sensitivity analysis was performed to measure the effect of drought on WELF efficiency, a decrease of about 13% on average WELF efficiency was observed. Outputs improvement was recommended for each country: Lithuania (14%), Mexico (10%) and 11% for Hungary, Latvia, and Turkey due to their high inefficiency. The study provides a robust framework for policy making and shows that a win-win strategy for the nexus must be implemented to achieve WELF-Nexus efficiency, given the trade-offs within its sectors. Furthermore, it highlights that innovative-driven policies will enhance WELF-Nexus efficiency and sustainability.

The water-energy-food (WEF) nexus is a complex system operating at many scales, the importance of which is increasingly recognized in academia and policy. There are calls to expand the nexus to include land and climate (WEFLC) as well as to narrow the science-policy divide, implying conducting assessments at policy-relevant scales to assess the impacts of policy objectives. This paper presents a national-scale WEFLC nexus system dynamics modelling assessment for Latvia. Qualitative and quantitative assessment was performed with local stakeholders to validate model structure, data, results, and to gather information on Latvian policy objectives and implement them in the model as potential future policies. Under baseline conditions (i.e. without implementing goal-specific policies under shared socio-economic pathway 2), results indicate a levelling off of consumption by 2050 while production of food products and energy is expected to increase. Nitrogen losses and climate emissions increase, going against policy targets. Implementation of indicative policies has desired impacts within their given sector, but may lead to trade-offs in others. Implementing multiple policies simultaneously may augment or hinder progress towards objectives due to system interconnectedness. Therefore, when choosing which policies to implement, cross-sectoral implications must be carefully considered. This work offers insight for policy and decision making in Latvia, hinting at policy options to pursue, and highlighting those to avoid. This study offers suggestions for closing the science-policy divide including the use of visual serious game environments for results interpretation, the use of selected indicators for nexus performance assessment, and close stakeholder engagement throughout a project.