Reactive nitrogen requirements to feed the world in 2050 and potential to mitigate nitrogen pollution

Abstract

Reactive nitrogen (Nr) is an indispensable nutrient for agricultural production and human alimentation. Simultaneously, agriculture is the largest contributor to Nr pollution, causing severe damages to human health and ecosystem services. The trade-off between food availability and Nr pollution can be attenuated by several key mitigation options, including Nr efficiency improvements in crop and animal production systems, food waste reduction in households and lower consumption of Nr-intensive animal products. However, their quantitative mitigation potential remains unclear, especially under the added pressure of population growth and changes in food consumption. Here we show by model simulations, that under baseline conditions, Nr pollution in 2050 can be expected to rise to 102-156% of the 2010 value. Only under ambitious mitigation, does pollution possibly decrease to 36-76% of the 2010 value. Air, water and atmospheric Nr pollution go far beyond critical environmental thresholds without mitigation actions. Even under ambitious mitigation, the risk remains that thresholds are exceeded.

Nutrients in the nexus

“…This budget appears arithmetically balanced, and in the real world, it must be balanced due to conservation of mass, but each of the specific flux estimates of N shown in the figure has an uncertainty of about ±10-20 % and possibly more owing to difficulties in measuring these fluxes and in scaling local measurements to global estimates. Despite such uncertainties in global estimates, it is clear than synthetic fertilizer inputs to agricultural systems, including livestock production, are larger than all natural N inputs combined (Bodirsky et al 2014, Sutton et al 2013. Of the estimated 122 Tg N in annual crop production, less than 20 % goes directly to feed humans while the rest feeds livestock.…”

Science and policy characteristics of the Paris Agreement temperature goal

“…In addition, many factors affecting crop yield projections -such as elevated CO 2 and ozone concentrations 25,26 as well as management options 27,28 , nitrogen limitations 29 and the impact of heat extremes 30 -are not well-constrained and are represented very differently across agricultural models 31 . Observational evidence indicates that substantial impacts of extremes on crop yields are already evident in the second half of the twentieth century 32 .…”

Nitrogen footprints: Regional realities and options to reduce nitrogen loss to the environment

“…Since diets based on less animal protein have been shown to be healthier (Tilman and Clark 2015) and have smaller N footprints (Stevens et al 2014), effective communication to the public of the impacts of dietary choices using N footprints may lead to a reduction in N pollution. The reducing Nr loss to the environment through shifting diets would provide co-benefits for greenhouse gas emissions (Bodirsky et al 2014;Westhoek et al 2014Westhoek et al , 2015.…”