We used the global dynamic land-use model GLOBIOM to assess the risk of food insecurity when meeting N boundaries and to investigate the effects of various sustainability options. First, we improved GLOBIOM by adding extended representations of the N cycle in global agricultural systems. The model was then applied under the constraint of meeting the regionally derived N boundaries given by an acceptable N surplus based on a critical N limit in surface water. Our indicators of food security are represented by the dietary energy availability and the dietary protein availability (indicators of food availability) and by the number of people at risk of hunger and food prices (indicators of food access).
GLOBIOM is a global partial equilibrium model allocating land-based activities (that is, management of cropland, livestock systems and forestry) under land availability constraints, to maximize the sum of producer and consumer surpluses26. The model relies on a geographically explicit representation of land-based activities at a 0.5° × 0.5° grid cell resolution. Agricultural production is represented for 18 crops (barley, dry beans, cassava, chick peas, corn, cotton, groundnut, millet, oil palm, potatoes, rapeseed, rice, soybeans, sorghum, sugar cane, sunflower, sweet potatoes and wheat) and seven types of livestock (dairy and other bovines (comprising cattle and buffalos), dairy and other sheep and goats, laying hens and broilers, and pigs), the outputs of which are processed to supply the food, feed and bioenergy markets. Each of the activities is described at the grid cell level through technological parameters provided by a specific biophysical model: EPIC41 for crops, EPIC and CENTURY42 for grassland, RUMINANT43 for livestock, and G4M44 for forestry. For a detailed description of the model, including the biophysical models, the representations of land-use competition and trade, exogenous scenario drivers and their assumptions, and endogenous model behaviour, see Supplementary Note 2. Our socio-economic narrative is parameterized following SSP2 (ref. 30). It includes quantified assumptions of economic and population developments, energy intensity improvements, energy resources, bioenergy resources and use, technology cost developments, and land-use developments (see Table 1 of ref. 30 for the details). The detailed quantifications and assumptions in SSP2 on the development of crop yields and input intensity, livestock feed conversion efficiency and productivity growth, as well as food demand and losses and wastes (including their differences from other SSPs), can be found in Sections 2.7 and 4.2 and Table 1 of ref. 30. How the SSP2 implementation compares with the other SSPs (and how GLOBIOM differs from other integrated assessment models (IAMs)) for demand and yields has been extensively discussed in refs. 45,46,47,48. The model is run in a dynamic, recursive setting with ten-year steps…