Signal Phosphorus at 18.2 and nitrogen fixation at 165 Tg per year

Summary

Of the two biogeochemical control variables, mined phosphorus applied to cropland stands at 18.2 Tg a year, above both the 6.2 Tg boundary and the 11.2 Tg high-risk line, and intentional nitrogen fixation for agriculture reaches 165 Tg a year, far above the 62 Tg boundary and 82 Tg high-risk line. One teragram equals a million tonnes, and with no new control-variable data this year, both values are unchanged from last year. Before human intervention, phosphorus flowed from land to freshwater at about 2.5 Tg a year, and the boundary uses a regional freshwater eutrophication limit that is stricter than the ocean boundary. The nitrogen figure combines industrial Haber-Bosch fixation and biological fixation by legumes and has risen steadily with cropland expansion and higher application rates. This year the spatial analysis was refined, including recalculating the nitrogen risk map using nitrogen surplus, but the formal global assessment is unchanged. Both nutrient boundaries remain classified as strongly transgressed.