Food Security continues to be elusive in Sub-Saharan Africa (SSA), several decades after the first World Food Summit in 1974. The causes of food insecurity in Sub-Saharan Africa include among others; poverty, economic constraints, agricultural and agronomical challenges, rapid population growth, and the effects of adverse climate change. These causes however, are linked to complex interactions, constraints and dependencies amongst the key physical resources in food systems, namely-Water, Land, Energy and Soil Nutrients (WLEN). There is limited insight on the combined impacts of the resource nexus, and how this may constrain the performance of food systems in Sub-Saharan Africa. This understanding is essential if the food challenges in the region are to be tackled sustainably. This study provides a detailed analysis of the Uganda's 2012 WLEN nexus resources vis-àvis the country's current and potential food demand using calorific-demand analysis and source-to-service resource transformation modelling. The analysis determines estimates of the current resource stresses within Uganda's insufficient food system and the interconnected resource implications for the achievement of food security by 2050. The results are visualised using Sankey diagrams. The inferences highlight evident limits across all four resources. Overall, the analysis helps to inform food security policy and the resource context for the present and future management of Uganda's food system.

Despite efforts to achieve food security in Sub-Saharan Africa (SSA) since the 1970's, food insufficiency continues to plague the region. As of 2014 more than a fifth of Sub-Saharan Africa's population-remain food insecure according to the United Nations Food and Agricultural Organisation (FAO). The food security challenges in Sub-Saharan Africa are linked to economic, agro-ecological, technological/agronomic, institutional and related factors. These causes however overlay complex interactions and constraints within the key physical resources of Water Land and Energy (WLE), which are necessary for food production, processing, distribution and consumption. The relationship between the WLE interactions and the performance of SSA's food systems, and the impacts of interventions at different scales are not yet fully understood, particularly in light of the need to maintain essential ecosystem services. This study employs an integrated multi-scale Food System resource analysis approach to examine Uganda's WLE resource constraints vis-à-vis 2012 and 2050 agricultural resource demand at national, district and local scales, as a test case for Sub-Saharan Africa. The analysis identifies where the competing WLE resource constraints are and the variations from local (sub-county), regional, to national scale so that potential policy interventions can be appropriately targeted. The approach involves a combination of geo-spatial analysis, calorific-demand analysis and Source-to-Service resource transformation modelling. The results are visualised using coupled Sankey diagrams and resource stress maps. The analysis reveals the current competing demands and constraints at different scales, and helps to identify key resource intervention areas to resolve resource stress in Uganda's food system. The inferences highlight variations in the significance of resource stress at different analytical resolutions and constraints at different locations for the WLE resources. Overall, the analysis helps to inform food security policy and the resource context for the present and future management of Uganda's food system.