A new direction for tackling phosphorus inefficiency in the UK food system

Analyzing the phosphorus flow characteristics in the largest freshwater lake (Poyang Lake) watershed of China from 1950 to 2020 through a bottom-up approach of watershed-scale phosphorus substance flow model

Understanding the historical patterns of phosphorus (P) cycling is essential for sustainable P management and eutrophication mitigation in watersheds. Currently, there is a lack of long-term watershed-scale models that analyze the flow of P substances and quantify the socioeconomic patterns of P flow. This study adopted a watershed perspective and incorporated crucial economic and social subsystems related to P production, consumption, and emissions throughout the entire life cycle. Based on this approach, a bottom-up watershed P flow analysis model was developed to quantify the P cycle for the first time in the Poyang Lake watershed from 1950 to 2020 and to explore the driving factors that influence its strength by analyzing multi-year P flow results. In general, the P cycle in the Poyang Lake watershed was no longer a naturally dominated cycle but significantly influenced by human activities during the flow dynamics between 1950 and 2015. Agricultural intensification and expansion of large-scale livestock farming continue to enhance the P flow in the study area. Fertilizer P inputs from cultivation account for approximately 60% of the total inputs to farming systems, but phosphate fertilizer utilization continues to decline. Feed P inputs have continued to increase since 2007. The expansion of large-scale farming and the demand for urbanization are the main factors leading to changes in feed P input patterns. The P utilization rate for livestock farming (PUEa) is progressively higher than international levels, with PUEa increasing from 0.64% (1950) to 9.7% (2020). Additionally, per capita food P consumption in the watershed increased from 0.67 kg to 0.80 kg between 1950 and 2020. The anthropogenic P emissions have increased from 1.67 × 104 t (1950) to 8.73 × 104 t (2020), with an average annual growth rate of 2.41%. Watershed-wide P pollution emissions have increased by more than five-fold. Population growth and agricultural development are important drivers of structural changes in P flows in the study area, and they induce changes in social conditions, including agricultural production, dietary structure, and consumption levels, further dominating the cyclic patterns of P use, discharge, and recycling. This study provides a broader and applicable P flow model to measure the characteristics of the P cycle throughout the watershed social system as well as provides methodological support and policy insights for large lakes in rapidly developing areas or countries to easily present P flow structures and sustainably manage P resources.

Phosphorus price spikes: A wake-up call for phosphorus resilience

Food systems depend on reliable supplies of phosphorus to fertilize soils. Since 2020, a pandemic, geopolitical disputes, trade wars and escalating fuel prices have driven a >400% increase in phosphorus commodity prices, contributing to the current food crisis. The Russia-Ukraine conflict has disrupted phosphate trade further. Concurrently, phosphorus losses to freshwaters, through insufficient municipal wastewater treatment and inappropriate fertilizer use and land management practices, are a significant threat to water quality globally. Despite precariously balanced food and water security risks, nations are largely unaware of their “phosphorus vulnerability” and phosphorus is markedly absent in national and global policies addressing food and water security. Phosphorus vulnerability can be described as the degree to which people/systems are susceptible to harm due to the physical, geopolitical and socio-economic dimensions of global phosphorus scarcity and pollution. Here, we bring the current price spike into focus, highlighting the drivers, policy responses and their consequences. We highlight the need for an integrated assessment of phosphorus vulnerability that considers environmental, socio-economic and climate change risks across scales. We illustrate how reducing phosphorus waste, increasing phosphorus recycling, and wider system transformation can reduce national reliance on imported phosphorus, whilst enhancing food and water security. The current crisis in fertilizer prices represents a wake-up call for the international community to embrace the global phosphorus challenge.