Phosphorus, food, and future challenges: Sustainable solutions to avoiding famine through closing the human phosphorus cycle

Background/Question/Methods
Industrialized agriculture is a dominant and highly visible feature of the current Anthropocene Epoch. This “Green Revolution” followed agronomic innovations coupled to invention of the Haber-Bosch process, which allowed humans to fix atmospheric nitrogen (N) for fertilizer, and is responsible for a three-fold increase in food production in the last 50-75 years. However, it is not well appreciated that these increases in crop production also required a concurrent increase in the use of inorganic phosphorus (P) that have been met by a massive expansion of P-rich mineral deposit mining. Industrial N-fixation may be rendered sustainable in the long-term if its dependence on fossil energy is minimized. However, a sustainable P supply is not assured because P deposits are regenerated only on geologic time scales.

Results/Conclusions

In short, the current model for food production is dependent on P supplies that are effectively non-renewable and are being depleted. Notably, because all life depends on P, it is effectively a non-substitutable necessity for both humans and the ecosystems on which we depend. Furthermore, mineral P deposits are not distributed evenly across the earth, suggesting that future P scarcity [and associated limitations on food production] may have national security implications. Indeed, some projections show mineral P reserves being depleted within decades—a prediction that is exacerbated by the increasing prevalence of P-rich diets worldwide and the expanding biofuels demand for P fertilizers. Phosphorus-induced famine is thus within the realm of possibility, particularly in developing countries where subsistence farmers are very sensitive to commodity prices. Such a future is ominous, but sustainable solutions to P challenges exist. Fundamentally, these solutions involve closing the human P cycle. We review the current state of knowledge about human P use and dependence and present examples of sustainable solutions in the context of the human P cycle.