National phosphorus planning for food and environmental security.

The dependence of countries on phosphorus fertilisers derived from phosphate rock to maintain crop yields and ensure food security is well established. Yet, exposure of national food systems to constrained reserves of phosphate rock and supply chain complexities still pose risks to farmers' access to this critical nutrient in many countries. Whilst phosphorus scarcity can threaten food security, suboptimal fertiliser use and poor wastewater treatment can lead to pollution of freshwaters and coasts, causing eutrophication. This impacts biodiversity, drinking water and aquatic food production. In some countries, national plans targeting the recycling of phosphorus losses back into food production are being considered, offering environmental and socio-economic benefits. Here, we review the literature on assessing risks to food security and water quality associated with national reliance on phosphate rock as the primary source of phosphorus for fertilisers. The scientific community has developed data and tools to enable countries to assess exposure in food systems from phosphorus supply and management and in the environment from pollution. However, current assessment approaches often overlook economic vulnerability, a key gap that hinders our understanding of the urgency and severity of impacts from inaction. Exposure assessments could be used to develop National Sustainable Phosphorus Plans embedding priority actions and financial instruments across existing policy frameworks. Actions include identifying local to national sources and sites for phosphorus recycling, identifying catchments and ecosystems where the benefits of reducing phosphorus pollution are greatest, and establishing an infrastructure development plan to enable greater recycling and reduced pollution. We discuss four integrated actions that will enable countries to take the first steps towards a circular phosphorus economy in the context of a challenging global situation.