Scientific Targets for Healthy Diets* Food group Food subgroup Reference diet (g/day) Possible ranges (g/day) Whole Grains All grains 232 0 to 60% of energy Tubers/Starchy Vegetables Potatoes, cassava 50 0 to 100 Vegetables All vegetables 300 200 to 600 Fruits All Fruits 200 100 to 300 Dairy Foods Dairy Foods 250 0 to 500 Beef, lamb, pork 14 0 to 28 Protein Sources Chicken, other poultry 29 0 to 58 Eggs 13 0 to 25 Fish 28 0 to 100 Dry beans, lentils, peas 50 0 to 100 Soy 25 0 to 50 Nuts 50 0 to 75 Added fats Unsaturated oils 40 20-80 Added sugars All sweeteners 31 0 to 31 * See Table 1 for a complete list of scientific targets for a 2500 kcal/day healthy reference diet The Commission has integrated, with the quantification of universal healthy diets, global scientific targets for sustainable food systems. The objective is to provide scientific boundaries to reduce environmental degradation arising from food production at all scales. The quantification of scientific targets for the safe operating space of food systems in the world, was done for the key environmental systems and processes where food production plays a dominant role in determining the state of the planet. There is strong scientific evidence that food production is among the largest drivers of global environmental change due to its contributions to greenhouse gas (GHG) emissions, biodiversity loss, freshwater use, eutrophication, and land-system change (as well as chemical pollution, which is not assessed by this Commission). In turn, food production depends upon the continued functioning of these biophysical systems and processes in regulating and maintaining a stable Earth system. These systems and processes thereby provide a necessary set of globally systemic indicators of what constitutes sustainable food production. The Commission concludes that these quantitative scientific targets for sustainable food systems, constitute universal and scalable planetary boundaries for the food system, (Table 2). However, the uncertainty range for these food boundaries remain high, due to the inherent complexity in Earth system dynamics from local ecosystems to the functioning of the biosphere and the climate system. Scientific Targets for Sustainable Food Production Earth system process Control variable Boundary Uncertainty Range Climate change GHG (CH4 and N2O) emissions 5 Gt CO2-eq yr-1 (4.7-5.4 Gt CO2-eq yr-1) Nitrogen cycling N application 90 Tg N yr-1 (65-90 Tg N yr-1) (90-130 Tg N yr-1) Phosphorus cycling P application 8 Tg P yr-1 (6-12 Tg P yr-1) (8-16 Tg P yr-1) Freshwater use Consumptive water use 2,500 km 3 yr-1 (1000-4000 km 3 yr-1) Biodiversity loss Extinction rate 10 E/MSY (1-80 E/MSY) Land-system change Cropland use 13 M km 2 (11-15 M km 2)

The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

Abstract. Atmospheric nitrogen (N) deposition is a recognized threat to plant diversity in temperate and northern parts of Europe and North America. This paper assesses evidence from field experiments for N deposition effects and thresholds for terrestrial plant diversity protection across a latitudinal range of main categories of ecosystems, from arctic and boreal systems to tropical forests. Current thinking on the mechanisms of N deposition effects on plant diversity, the global distribution of G200 ecoregions, and current and future (2030) estimates of atmospheric N-deposition rates are then used to identify the risks to plant diversity in all major ecosystem types now and in the future.This synthesis paper clearly shows that N accumulation is the main driver of changes to species composition across the whole range of different ecosystem types by driving the competitive interactions that lead to composition change and/or making conditions unfavorable for some species. Other effects such as direct toxicity of nitrogen gases and aerosols, long-term negative effects of increased ammonium and ammonia availability, soil-mediated effects of acidification, and secondary stress and disturbance are more ecosystem-and site-specific and often play a supporting role. N deposition effects in mediterranean ecosystems have now been identified, leading to a first estimate of an effect threshold. Importantly, ecosystems thought of as not N limited, such as tropical and subtropical systems, may be more vulnerable in the regeneration phase, in situations where heterogeneity in N availability is reduced by atmospheric N deposition, on sandy soils, or in montane areas.Critical loads are effect thresholds for N deposition, and the critical load concept has helped European governments make progress toward reducing N loads on sensitive ecosystems. More needs to be done in Europe and North America, especially for the more sensitive ecosystem types, including several ecosystems of high conservation importance.The results of this assessment show that the vulnerable regions outside Europe and North America which have not received enough attention are ecoregions in eastern and southern Asia (China, India), an important part of the mediterranean ecoregion (California, southern Europe), and in the coming decades several subtropical and tropical parts of Latin America and Africa. Reductions in plant diversity by increased atmospheric N deposition may be more widespread than first thought, and more targeted studies are required in low background areas, especially in the G200 ecoregions.

The food system is a major driver of climate change, land-use change, depletion of freshwater resources, and pollution of aquatic and terrestrial ecosystems by excessive nitrogen and phosphorus inputs. Here we show that as a result of expected changes in population and income levels, the environmental impacts of the food system could increase by 60-90% between 2010 and 2050 in absence of technological changes and dedicated mitigation measures, and reach levels that are beyond planetary boundaries that define a safe operating space for humanity. We analyse several options for reducing the environmental impacts of the food system, including dietary changes towards healthier, more plant-based diets, improvements in technologies and management, and reductions in food loss and waste. We find that no single measure is enough to simultaneously stay within all planetary boundaries, and combining each measure synergistically will be needed to sufficiently mitigate the projected increase in environmental pressures.

The demand for more food is increasing fertilizer and land use, and the demand for more energy is increasing fossil fuel combustion, leading to enhanced losses of reactive nitrogen (N r ) to the environment. Many thresholds for human and ecosystem health have been exceeded owing to N r pollution, including those for drinking water (nitrates), air quality (smog, particulate matter, ground-level ozone), freshwater eutrophication, biodiversity loss, stratospheric ozone depletion, climate change and coastal ecosystems (dead zones). Each of these environmental effects can be magnified by the ‘nitrogen cascade’: a single atom of N r can trigger a cascade of negative environmental impacts in sequence. Here, we provide an overview of the impact of N r on the environment and human health, including an assessment of the magnitude of different environmental problems, and the relative importance of N r as a contributor to each problem. In some cases, N r loss to the environment is the key driver of effects (e.g. terrestrial and coastal eutrophication, nitrous oxide emissions), whereas in some other situations nitrogen represents a key contributor exacerbating a wider problem (e.g. freshwater pollution, biodiversity loss). In this way, the central role of nitrogen can remain hidden, even though it actually underpins many trans-boundary pollution problems.