As of 2022, 93% of mineral phosphorus is used for food production and 7% for non-food products. Section 2.1 presents an analysis that predicts, all else remaining constant, a GDP-driven increase of 40% in phosphorus and related environmental resources by 2060. A bifurcation between developed and least developed countries is expected, however. On the one hand, although 80% of the world’s population will not increase by 2060, the demand for fertilizer will increase due to dietary changes toward increased meat consumption. On the other, the population of 20% of Middle Africa will increase by 182% without experiencing any significant change in GDP per capita or diet. That increase can be partly mitigated by the more efficient use of phosphorus for food as well as technological innovation. Significant potential for improving technology and its use is indicated by a total phosphorus (P) use efficiency (P-TUE) of far less than 10%, meaning that less than 10% of phosphorus used for food is absorbed by food. In turn, Sects. 2.2–2.4 offer detailed insights into the magnitude of phosphorus flows for different uses in food production as well as non-food uses, including increasing future demands (e.g., for car batteries). Because the challenge of managing phosphorus sustainably requires an integrated perspective on the different uses and demands for which strong increases can be expected, special attention is paid to phosphorus demand and different options to increase the efficiency of phosphorus use. In that case, the most comprehensive perspective is the society–technology–systems (STES) perspective, in which the climate–water–soil–biomass nexus is presented as a submodel of the environment. Last, for a deeper understanding of the system’s properties, Sect. 2.5 discusses the role of system dynamics and sustainable phosphorus flux analysis.