Can the availability of mineral nutrient be an obstacle to the development of organic agriculture at the global scale ?

Organic agriculture is often proposed as a promising approach to achieve sustainable food systems while minimizing environmental impacts. Its capacity to meet the global food demand remains, however, debatable. Some studies have investigated this question and have concluded that organic farming could satisfy the global food demand provided that animal product consumption and food waste are reduced. However, these studies have not fully considered the changes in the type of crops grown that occur when conventional farming systems are converted to organic farming. Most importantly, they also have missed a critical ecological phenomenon by not considering the key role that nitrogen (N) cycling plays in sustaining crop yields in organic farming. In this study, we first carried out a global meta-analysis comparing organic vs conventional crop rotations. Based on these results, we developed global spatial explicit maps of the type of crop grown if organic farming was to drastically expand. We then estimated organic global food production using GOANIM (Global Organic Agriculture NItrogen Model), a spatially explicit, biophysical and linear optimization model simulating N cycling in organically managed croplands and its feedback effects on food production. GOANIM explores N flows between croplands, livestock animals and permanent grasslands, and with conventional farming systems. The model optimizes livestock populations at the local scale in order to maximize N supply from livestock manure – hence maximizing cropland production –, while minimizing the animals’ competition for grain food resources. We used GOANIM to simulate several supply-side scenarios of global conversion to organic farming. We then compared the outcomes of these scenarios with different estimates of the global demand, thus leading to complete exploration of the global production-demand options space. We show N deficiency would be a major limiting factor to organic production in a full organic world, leading to an overall -37% reduction in global food availability. Nevertheless, we also show that lower conversion shares (up to 60%) would be feasible in coexistence with conventional farming when coupled with demand-side solutions, such as reduction of the per capita energy intake or food wastage. This work substantially contributes to advancing our understanding of the role that organic farming may play to reach fair and sustainable food systems, and it indicates future pathways for achieving global food security