Trend Nitrogen and phosphorus flows far beyond safe levels

Summary

The biogeochemical flows boundary is measured by mined phosphorus applied to cropland and intentional nitrogen fixation for agriculture, at 18.2 Tg and 165 Tg a year against boundaries of 6.2 Tg and 62 Tg, both in the high-risk zone. Industrial nitrogen fixation and phosphate mining drove a surge in fertilizer use during the twentieth century, and human nitrogen inputs now exceed all natural sources combined. Excess nutrients cause polluted water, algal blooms, oxygen-starved dead zones, biodiversity loss and nitrogen air pollution, threatening fisheries, drinking water, food and health. Regionally, agricultural nitrogen has crossed safe limits in parts of Asia and Europe, and nutrient flows are still rising sharply in Asia. The report observes that phosphorus built up in soils and nitrogen in groundwater can linger for decades, so harm may continue well after inputs are cut.