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Excess reactive nitrogen (Nr) in the global system has led to a wide variety of environmental and human health problems. To minimize the negative impacts of nitrogen loss from agriculture, we need to develop more sustainable farming systems that can efficiently produce food for humans while balancing ecological functioning and reducing Nr losses. This paper looks at recent research examining Nr losses in organic systems, using conventional Nr losses in the United States (U.S.) as a baseline to identify leverage points for reducing Nr loss. The paper discusses the sources of Nr used in organic versus conventional farming and highlights the importance of increasing the use of recycled Nr to prevent additional Nr loss to the environment. Specifically, we note that organic production is advantageous when it comes to the creation of new Nr because of its reliance on recycled sources of Nr, improved ability to access nutrients in the soil, and higher residue recycling rates. We also highlight areas where additional research, policies, and protocols are needed to improve Nr efficiency, including increasing organic yields, increased recycling of processing waste, matching nutrient flows, reducing and recycling edible food waste, and examining potential benefits and risks of land application of sewage sludge in organic systems.

Christian Junge (1912–1996) is considered by many to be the founder of the modern discipline of atmospheric chemistry. In studies from the 1950s through the 1970s, Junge was able to link chemical measurements in a few scattered locations around the earth and integrate them with meteorology to develop the first global view of the basic chemical and physical processes that control the sources, transport, transformations, and fate of particles and gases in the atmosphere. In this paper we summarize and comment upon a number of Junge’s seminal research contributions to atmospheric chemistry, including his discovery of the stratospheric sulfate layer (known as the Junge layer), his recognition of the relationship between the variability of the concentrations of trace gases and their atmospheric lifetimes, his studies of aerosol size and number distributions, his development of the first quantitative model of tropospheric ozone, and other significant scientific investigations. We also discuss Junge’s professional life, his many international leadership positions and honors, as well as some memories and reflections on his many abilities that led to his outstanding contributions to the science of atmospheric chemistry.

Phosphorus (P) and nitrogen (N) are essential nutrients for food production but their excess use in agriculture can have major social costs, particularly related to water quality degradation. Nutrient footprint approaches estimate N and P release to the environment through food production and waste management and enable linking these emissions to particular consumption patterns. Following an established method for quantifying a consumer-oriented N footprint for the United States (U.S.), we calculate an analogous P footprint and assess the N:P ratio across different stages of food production and consumption. Circa 2012, the average consumers P footprint was 4.4 kg P capita(-1) yr(-1) compared to 22.4 kg N capita(-1) yr(-1) for the food portion of the N footprint. Animal products have the largest contribution to both footprints, comprising >70% of the average per capita N and P footprints. The N:P ratio of environmental release based on virtual nutrient factors (kilograms N or P per kilogram of food consumed) varies considerably across food groups and stages. The overall N:P ratio of the footprints was lower (5.2 by mass) than for that of U.S. food consumption (8.6), reinforcing our finding that P is managed less efficiently than N in food production systems but more efficiently removed from wastewater. While strategies like reducing meat consumption will effectively reduce both N and P footprints by decreasing overall synthetic fertilizer nutrient demands, consideration of how food production and waste treatment differentially affect N and P releases to the environment can also inform eutrophication management. Funding Agencies|National Academies of Science Research Associateship Program through US EPA [CQ-83557701]; Trottier Institute for Science and Public Policy (TISPP); Natural Sciences and Engineering Research Council of Canada (NSERC)Natural Sciences and Engineering Research Council of Canada; NSF INFEWS grant [NSF EAR1639458]

The social cost of nitrous oxide does not account for stratospheric ozone depletion. Doing so could increase its value by 20%. Links between nitrous oxide and other nitrogen pollution impacts could make mitigation even more compelling.

Nitrogen management is on the cusp of becoming a major global policy issue — the international community is gradually acknowledging that the feasibility of an array of environmental, health and food security goals hinges on how humanity manages nitrogen as a resource and a pollutant over the coming decades. As a result, the nitrogen research agenda should expand to consider more policy-relevant questions, such as the power dynamics of the broader food system and the many influences on farmer decision-making. Doing so demands much closer collaboration between the natural and social sciences, from problem formulation to research execution, which requires overcoming a range of ideological, institutional and knowledge barriers.

Global livestock supply chains have significantly altered nitrogen (N) flows over past years, thereby threatening environmental and human health. Here, we provide a disaggregated assessment of the livestock sector’s impacts on global N flows and emissions, including international trade. The results show that the sector currently emits 65 Tg N yr−1, equivalent to one-third of current human-induced N emissions and sufficient to meet the planetary boundary for N. Of that amount, 66% is allocated to Asia and 68% is associated with feed production. Most emissions originate from locally produced animal-sourced food, although N emissions embedded in international trade are significant for some importing countries. Given the magnitude of its impacts and its central role in both domestic and international N challenges, the livestock sector urgently requires a global initiative to tackle N pollution while supporting food security. Livestock greenhouse gas emissions are key to the sustainability of food systems. A spatially explicit analysis of global livestock supply chains shows large variability of nitrogen use efficiency across species, systems, production intensities and the origin and management of animal feed.

Our aim in this paper is to describe an opportunity for physics students and faculty to learn about an environmental issue of much current interest: the quantification, or footprint analysis, of carbon dioxide (CO2) and reactive nitrogen emissions. These can originate from human activities such as energy use, food consumption, and transportation, and are among the greenhouse gases (GHG) that contribute to global warming and rising sea levels. Moreover, nitrogen compounds also have effects on the chemistry and biology of the environment. Analyzing both of these footprints together captures multiple environmental impacts from the local to the global levels and can suggest mitigation strategies. We focus on the experiences of interdisciplinary teams, which included physics students and faculty, and that used the leading greenhouse gas analysis platform SIMAP (Sustainability Indicator Management and Analysis Platform).

Background: Acute kidney injury (AKI) is common among patients hospitalised with COVID-19, and associated with worse prognosis. The aim of this study was to investigate the epidemiology, risk factors and outcomes of AKI in patients with COVID-19 in a large UK tertiary centre. Methods: We analysed data of consecutive adults admitted with a laboratory-confirmed diagnosis of COVID-19 across two sites of a hospital in London, UK, from 1st January to 13th May 2020. Results: Of the 1248 inpatients included, 487 (39%) experienced AKI (51% stage 1, 13% stage 2,and 36% stage 3). The weekly AKI incidence rate gradually increased to peak at week 5 (3.12 cases/100 patient-days), before reducing to its nadir (0.83 cases/100 patient-days) at the end the study period (week 10). Among AKI survivors, 84.0% had recovered renal function to pre-admission levels before discharge and none required on-going renal replacement therapy (RRT). Pre-existing renal impairment [odds ratio (OR) 3.05, 95%CI 2.24-4,18; pConclusions: This large UK cohort demonstrated a high AKI incidence with a changing pattern over time and was associated with increased mortality even at stage 1. Inpatient diuretic use was linked to a higher AKI risk. One third of survivors with AKI3 exhibited newly established renal impairment already at 3-6 months.

Acid deposition, resulting from the atmospheric transport of acidifying compounds emitted during the combustion of fossil fuels, has historically resulted in stream acidification in many headwater streams in the eastern United States, including streams in Shenandoah National Park (SHEN). Though restrictions on these emissions were established by an amendment to the Clean Air Act in 1990, reductions in stream acidification have not been observed in all regions of SHEN due to variations in the geological composition of SHEN watersheds. Before the implementation of these restrictions, fish assemblages were strongly controlled by a stream’s acid neutralizing capacity (ANC), which is the ability of a watershed to buffer acid inputs. This study investigated changes in the relationship between fish assemblages and ANC within SHEN 21 years after implementation of more stringent restrictions on the emission of sulfur and nitrogen oxides in 1995. Results indicated that recovery trends in water chemistry were observed in some SHEN watersheds; however, fish species richness and total fish biomass continue to be influenced by the legacy of acid deposition in acid sensitive watersheds. Temporal trend analysis indicated little change in ANC within acid sensitive watersheds and minor decreases in stream sulfate concentrations. These findings indicate a persistent impact from previously deposited sulfur oxides and the continued influence of these compounds on fish assemblages within SHEN. Though no further loss of fish species, and in some cases, increases in species richness, suggest the early stages of recovery, many SHEN streams remain as susceptible to acidification as they were over two decades ago, highlighting the need for continued regulation of acidifying emissions and conservation efforts in headwater streams.

The Shenandoah Watershed Study (established in 1979) and the Virginia Trout Stream Sensitivity Study (established in 1987) serve to increase understanding of hydrological and biogeochemical changes in western Virginia mountain streams that occur in response to acidic deposition and other ecosystem stressors. The SWAS-VTSSS program has evolved over its 40+ year history to consist of a temporally robust and spatially stratified monitoring framework. Currently stream water is sampled bi-hourly during high-flow events at 3 sites and weekly at 4 sites within Shenandoah National Park (SHEN), and quarterly at 72 sites and on an approximately decadal frequency at ~ 450 sites within the wider western Virginia Appalachian region. Stream water is evaluated for pH, acid neutralizing capacity (ANC), base cations (calcium, magnesium, sodium and potassium ion), acid anions (sulfate, nitrate and chloride), silica and ammonium, with a subset of samples evaluated for monomeric aluminum and dissolved organic carbon. Hourly stream discharge (4 sites) and in-situ measurements of conductivity, water and air temperature (3 sites) are also measured within SHEN. Here we provide an overview and timeline of the SWAS-VTSSS stream water monitoring program, summarize the field and laboratory methods, describe the water chemistry and hydrologic data sets, and document major watershed disturbances that have occurred during the program history. Website links and instructions are provided to access the stream chemistry and time-series monitoring data in open-access federal databases. The purpose of this publication is to promote awareness of these unique, long-term data sets for wider use in catchment studies. The water chemistry and hydrologic data can be used to investigate a wide range of biogeochemical research questions and provide key inputs for models of these headwater stream ecosystems. SWAS-VTSSS is an ongoing program and quality assured data sets are uploaded to the databases annually.

More food and energy allow for more people who then require more food and energy, and so it has gone for centuries. At the same time, economic progress leads to a different lifestyle with an increasing demand for energy and food, also accelerating food waste. Fueling this food-energy-population dynamic is an ever-increasing conversion of unreactive dinitrogen (N2) to reactive N (Nr), which then results in a cascade of positive (food and energy for people) and negative (damage to people, climate, biodiversity, and environment) impacts as Nr is distributed throughout Earth systems. The most important step in reducing the environmental impacts of Nr is limiting its human-based creation. In this article, therefore, we focus on this most important first step: the conversion of N2 to Nr by human activities. Specifically, we examine Nr creation and use (they are different!) on a global and regional basis and Nr use on a global and regional per capita basis. In addition, we introduce the metric Nr Use Index (NUI), which can be used to track and project Nr use relative to a fixed point in time. We then assess the progress in Nr management over the past 20 years. Our article presents a case study of the Netherlands to show what one country, beset by Nr-relatedproblems that have led to an N crisis, did to address those problems and what worked and what didn't work. The article concludes with an assessment of what the future might hold with respect to Nr creation and use, including a review of other projections. We expect that NUI will increase especially in Asia, Latin America, and Africa. The other parts of the world are consolidating or even decreasing NUI. In Latin America and Asia, there is limited agricultural land, and by increasing NUI for food the risk of Nr pollution is very high. The Netherlands has shown not only what effects can be expected with increasing NUI but also what successful policies can be introduced to limit environmental losses. Our assessment shows that Nr creation needs to be limited to prevent local to global environmental impacts.

The Shenandoah Watershed Study (established in 1979) and the Virginia Trout Stream Sensitivity Study (established in 1987) serve to increase understanding of hydrological and biogeochemical changes in western Virginia mountain streams that occur in response to acidic deposition and other ecosystem stressors. The SWAS-VTSSS program has evolved over its 40+ year history to consist of a temporally robust and spatially stratified monitoring framework. Currently stream water is sampled bi-hourly during high-flow events at 3 sites and weekly at 4 sites within Shenandoah National Park (SHEN), and quarterly at 72 sites and on an approximately decadal frequency at ~ 450 sites within the wider western Virginia Appalachian region. Stream water is evaluated for pH, acid neutralizing capacity (ANC), base cations (calcium, magnesium, sodium and potassium ion), acid anions (sulfate, nitrate and chloride), silica and ammonium, with a subset of samples evaluated for monomeric aluminum and dissolved organic carbon. Hourly stream discharge (4 sites) and in-situ measurements of conductivity, water and air temperature (3 sites) are also measured within SHEN. Here we provide an overview and timeline of the SWAS-VTSSS stream water monitoring program, summarize the field and laboratory methods, describe the water chemistry and hydrologic data sets, and document major watershed disturbances that have occurred during the program history. Website links and instructions are provided to access the stream chemistry and time-series monitoring data in open-access federal databases. The purpose of this publication is to promote awareness of these unique, long-term data sets for wider use in catchment studies. The water chemistry and hydrologic data can be used to investigate a wide range of biogeochemical research questions and provide key inputs for models of these headwater stream ecosystems. SWAS-VTSSS is an ongoing program and quality assured data sets are uploaded to the databases annually.

When prescribing any therapy, potential benefits must be balanced against risk. This is particularly relevant in rheumatoid arthritis (RA), where many treatments available have important associated adverse events. Awareness of adverse event profiles is crucial in supporting patient-centred care, particularly in situations where comparative efficacy data are sparse. In addition, the terminology surrounding adverse events and adverse reactions can be confusing and is often used in a contradictory fashion. Across the biologic class of therapy, head-to-head trials are infrequent, and it is often easier to make choices based on adverse event profile, rather than efficacy. This chapter will review patterns of adverse events seen with RA treatments, including by organ class.

Loss of work due to rheumatic and musculoskeletal diseases (RMDs), including rheumatoid arthritis (RA), causes a major socioeconomic burden to society. In Europe, RMDs affect more than 4 million people with an estimated societal cost of 0.5–2% of the gross domestic product. The peak age of onset for both men and women is before the age of ~65 years, typically the age of retirement in most countries meaning most people who develop RA are of working age at diagnosis. For many people work is important, improving self-esteem and self-worth, and contributing to financial independence. This chapter will review the impact, including economic aspects, of RA on work, personal and environmental factors associated with work outcomes, and management of problems at work or work loss.

Managing reactive nitrogen (Nr) to achieve a sustainable balance between production of food, feed and fiber, and environmental protection is a grand challenge in the context of an increasingly affluent society. Here, we propose a novel framework for national nitrogen (N) assessments enabling a more consistent comparison of the uses, losses and impacts of Nr between countries, and improvement of Nr management for sustainable development at national and regional scales. This framework includes four key components: national scale N budgets, validation of N fluxes, cost-benefit analysis and Nr management strategies. We identify four critical factors for Nr management to achieve the sustainable development goals: N use efficiency (NUE), Nr recycling ratio (e.g., ratio of livestock excretion applied to cropland), human dietary patterns and food waste ratio. This framework was partly adopted from the European Nitrogen Assessment and now is successfully applied to China, where it contributed to trigger policy interventions toward improvements for future sustainable use of Nr. We demonstrate how other countries can also benefit from the application our framework, in order to include sustainable Nr management under future challenges of growing population, hence contributing to the achievement of some key sustainable development goals (SDGs).

We estimated the reactive nitrogen (Nr) lost per unit food Nr consumed for organic food production in the United States and compared it to conventional production. We used a nitrogen footprint model approach, which accounts for both differences in Nr losses as well as differences in productivity of the two systems. Additionally, we quantified the types of Nr inputs (new versus recycled) that are used in both production systems. We estimated Nr losses from organic crop and animal production to be of comparable magnitude to conventional production losses, with the exception of beef. While Nr losses from organic vegetables are possibly higher (+37%), Nr losses from organic grains, starchy roots, legumes are likely of similar magnitude to conventional production (+7%, +6%, −12%, respectively). Nr losses from organic poultry, pigmeat, and dairy production are also likely comparable to conventional production (+9%, +10%, +12%, respectively), while Nr losses from organic beef production were estimated to be higher (+124%). Due to the high variability and high uncertainty in Nr efficiency in both systems we cannot make conclusions yet on the statistical significance of these potential differences. Conventional production relies heavily on the creation of new Nr (70%–90% of inputs are from new Nr sources like synthetic fertilizer), whereas organic production primarily utilizes already existing Nr (0%–50% of organic inputs are from new Nr sources like leguminous N fixation). Consuming organically produced foods has little impact on an individual’s food N footprint but changes the percentage of new versus recycled Nr in the footprint. With the exception of beef, Nr losses from organic production per unit N in product are comparable to conventional production. However, organic production requires the creation of less new Nr, which could reduce global Nr pollution.

Reactive nitrogen (Nr; all species of nitrogen other than N2 gas) is a major cause of air and water pollution, with worldwide costs of billions in human health and ecosystem damages. The nitrogen (N) footprint, which quantifies the anthropogenic release of Nr from the production and consumption of both food and energy, has been used as an indicator of sustainability at individual and national levels. Here, we present the first institutional N footprint in Australia – the N footprint for The University of Melbourne (UoM) in 2015, and projections to 2020 under four scenario families. The total N footprint of UoM in 2015 was 139 tonnes N; food production (36.7%), utilities (32.4%), and transport (28.1%) were the major contributors while food consumption and fertilizer usage made up the remaining 2.8%. Under a businessasusual scenario, the N footprint of UoM would grow by 13% to 157 tonnes N in 2020 due to increase in student and staff population and infrastructure development. However, UoM has the potential to reduce its N footprint by 59% relative to the 2015 baseline if it implements changes to food purchases and energy use by 2020. The mitigation strategies with the largest potential reduction should be prioritized, including shifting purchased electricity fuel sources to wind or solar (26% reduction) and reducing air travel emissions (25% reduction). We demonstrate the potential of the N footprint as a tool for an institution to assess and monitor the sustainability of its operations and governance. Universities are leading the way in sustainable development, and the calculation of N footprint for UoM is the starting point for future work on sustainable institutional Nr management in Australia.

Nitrogen (N) footprints quantify the anthropogenic release of reactive nitrogen (Nr) from resource consumption, but do not connect to the resulting environmental impacts. Australia has the largest measured N footprint, but is generally perceived as a “green and clean” country. To explore this discrepancy, we developed an indicator, Nr spatial intensity (NrSI) that estimates the intensity of the Nr loss on a per area basis. The system boundary of the N footprint is any resource consumption by an entity, regardless of where the Nr is released. In contrast, the NrSI framework maps the geographical locations of anthropogenic Nr losses. We found that the pattern of NrSI among nations was very different from that of their N footprint. Factors that affect the comparison include land area, population density, and the import and export of food. Australia had the lowest NrSI (6 kg N ha−1 yr−1) while the Netherlands had the highest NrSI (217 kg N ha−1 yr−1) of the seven nations studied. In concert with the N footprint, the NrSI could be used as a benchmark for assessing the environmental pressure from Nr in a nation and for setting priorities of mitigating Nr pollution to help achieve the Sustainable Development Goals by 2030.

We summarize past examples of the use of science to document the effectiveness of policy in air quality management. Our goal is to inform public discourse amidst attempts to negate the relevance and value of scientific data and fact-based analysis in favor of partisan opinion and ideology. Although air quality is fundamental to environmental and human health, air pollution has degraded natural systems and reduced economic and cultural benefits and services. The quality of air and fresh water across much of the United States vastly improved in recent decades in response to the Clean Air and Clean Water Acts and other rules and policies. We point to recently observed decreases in air pollution and its effects attributable to policy that have been informed by environmental monitoring and research. Examples include decreased environmental lead contamination due to the elimination of tetraethyl lead from gasoline, decreases in tropospheric ozone, improved visibility from reduced airborne particulate matter, declines in atmospheric sulfur and nitrogen deposition that acidify the environment and declines in atmospheric mercury and subsequent bioaccumulation of toxic methyl mercury. Pollutant reductions have provided environmental, social, and economic benefits, highlighting the urgency to apply these lessons to address current critical environmental issues such as emissions of greenhouse gases. These examples underscore the important role of data from long-term research and monitoring as part of fact-based decision-making in environmental policy.

Reducing nitrogen pollution across the food chain requires the use of clear and comprehensive indicators to track and manage losses. The challenge is to derive an easy-to-use robust nitrogen use efficiency (NUE) indicator for entire food systems to help support policy development, monitor progress and inform consumers. Based on a comparison of four approaches to NUE (life cycle analysis, nitrogen footprint, nitrogen budget, and environmental impact assessment), we propose an indicator for broader application at the national scale: The whole food chain (NUEFC), which is defined as the ratio of the protein (expressed as nitrogen) available for human consumption to the (newly fixed and imported) nitrogen input to the food system. The NUEFC was calculated for a set of European countries between 1980 and 2011. A large variation in NUEFC was observed within countries in Europe, ranging from 10% in Ireland to 40% in Italy in 2008. The NUEFC can be used to identify factors that influence it (e.g., the share of biological nitrogen fixation (BNF) in new nitrogen, the imported and exported products and the consumption), which can be used to propose potential improvements on the national scale.

The water footprint for fossil fuels typically accounts for water utilized in mining and fuel processing, whereas the water footprint of biofuels assesses the agricultural water used by crops through their lifetime. Fossil fuels have an additional water footprint that is not easily accounted for: ancient water that was used by plants millions of years ago, before they were transformed into fossil fuel. How much water is mankind using from the past to sustain current energy needs? We evaluate the link between ancient water virtually embodied in fossil fuels to current global energy demands by determining the water demand required to replace fossil fuels with biomass produced with water from the present. Using equal energy units of wood, bioethanol, and biodiesel to replace coal, natural gas, and crude oil, respectively, the resulting water demand is 7.39 × 1013 m3y−1, approximately the same as the total annual evaporation from all land masses and transpiration from all terrestrial vegetation. Thus, there are strong hydrologic constraints to a reliance on biofuel energy produced with water from the present because the conversion from fossil fuels to biofuels would have a disproportionate and unsustainable impact on the modern water. By using fossil fuels to meet today's energy needs, we are virtually using water from a geological past. The water cycle is insufficient to sustain the production of the fuel presently consumed by human societies. Thus, non-fuel based renewable energy sources are needed to decrease mankind's reliance on fossil fuel energy without placing an overwhelming pressure on global freshwater resources.

The development of nitrogen footprint tools has allowed a range of entities to calculate and reduce their contribution to nitrogen pollution, but these tools represent just one aspect of environmental pollution. For example, institutions have been calculating their carbon footprints to track and manage their greenhouse gas emissions for over a decade. This article introduces an integrated tool that institutions can use to calculate, track, and manage their nitrogen and carbon footprints together. It presents the methodology for the combined tool, describes several metrics for comparing institution nitrogen and carbon footprint results, and discusses management strategies that reduce both the nitrogen and carbon footprints. The data requirements for the two tools overlap substantially, although integrating the two tools does necessitate the calculation of the carbon footprint of food. Comparison results for five institutions suggest that the institution nitrogen and carbon footprints correlate strongly, especially in the utilities and food sectors. Scenario analyses indicate benefits to both footprints from a range of utilities and food footprint reduction strategies. Integrating these two footprints into a single tool will account for a broader range of environmental impacts, reduce data entry and analysis, and promote integrated management of institutional sustainability.

A nitrogen (N) footprint quantifies the amount of reactive nitrogen released to the environment and can be measured at different scales. The N footprint of a university includes activities and consumption within its geographic boundaries as well as activities that support the institution. Determining system bounds of an N footprint depends on the institution's mission and provides a common baseline for comparison. A comparison of three scopes of the N footprint, which describe how emissions are directly related to an institution's activities, was conducted for seven institutions. Scopes follow the established definition for the carbon footprint. In this article, the authors propose a new system bounds definition (core campus versus adjunct). Two case studies were explored: how the N footprint of Dickinson College changed with air travel, and how the N footprint of the Marine Biological Laboratory changed with scientific research. Of the three scopes, scope 3 was consistently the largest proportion of the N footprint for all seven institutions. The core campus activities of Dickinson College made up 99 percent of its N footprint, with air travel making up the remaining 1 percent. The Marine Biological Laboratory's core campus activities made up 51 percent of its N footprint and the scientific research made up the remaining 49 percent. Institutions should define system bounds based on their mission and stay consistent with their boundaries following the baseline year. The core campus footprint could be used to compare institution footprints using consistent system bounds. How institutions define their boundaries will impact the recorded amount of nitrogen as well as how the institution will set reduction strategies.

Following discussions at the 6th International Nitrogen Conference, Kampala (24th-27th November 2013), the delegates agreed the Kampala Statement-for-Action on Reactive Nitrogen in Africa and Globally. The Statement-for-Action highlights the global challenge of aiming for just enough nitrogen: enough to meet human needs for food, fuel and fibre, while avoiding excess that contributes to air and water pollution, climate change and ecosystem degradation. The following priorities for Africa are highlighted: (i) Sub-Saharan African agriculture needs to be part of the solution to regional and world food security. This will require restoring and sustaining the fertility of Sub-Saharan African soils through better use of fertilizers in combination with other nutrient sources, such as organic matter and biological fixation. (ii) Smart input subsidy schemes helping to trigger profitable nutrient use should take care that increases in fertilizer find a balance between food security and reducing environmental effects, while recognizing that, (iii) Africa is already facing environmental challenges of nitrogenous air and water pollution even with current levels of nitrogen input. Current nitrogen inputs are thought to be mainly from sources other than chemical nitrogen fertilizers (e.g., biological nitrogen fixation, organic nitrogen inputs, wastewater), though further study is needed to demonstrate apportionment between nitrogen sources and sinks. The following global priorities are highlighted: (i) Improving nitrogen management should be incorporated as a critical component across the Sustainable Development Goals. (ii) The benefits of reducing nitrogen losses from agriculture, industry, transport and energy, of improved waste treatment and of better-informed individuals and institutions should be highlighted, including an emphasis on innovative nutrient recycling and on equitable diet and energy choices. (iii) There is a need for innovation and increased awareness on the nitrogen challenge, including through better communication, education and training. (iv) Solutions to the nitrogen issue should be tuned to regional conditions and require cross-ministerial, trans-disciplinary, multi-sectoral cooperation to create effective policies that fulfill regional and global commitments.

Food and energy production have negative impacts due to the buildup of reactive nitrogen in the environment and subsequent nitrogen (N) impacts. To quantify the nitrogen footprint left in the environment by an individual, scientists from the University of Virginia USA developed a model to calculate nitrogen footprints, the N-Calculator, which transforms data on food and energy consumption into kg N per year lost into the environment. To calculate the average N footprint for an individual in the area of Lisbon, one thousand Lisbon inhabitants were surveyed at random using the N-Footprint questionnaire. The average N footprint estimated for Portugal was 25.5 kg N per capita per year and the average personal N footprint for the Lisbon area was 24.7 kg N per capita per year. The average N footprint for men and women was similar and, despite a tendency for people over the age of 65 to have a lower footprint, there was no statistical difference across the age groups studied (e.g., the N-Footprint for > 65 and 21–30 years of age was 23.5 and 25.8 kg N per capita per year, respectively). Losses of N to the environment were always higher for food consumption than for energy. Generally, the food types consumed do not comply with the recommendations of the Portuguese Association of Nutritionists for a healthy diet.

Food production--especially raising animals for meat--has a massive negative impact on the environment and contributes to global warming. To address this, we investigated whether information about food sustainability would increase purchases of sustainable foods by patrons of university cafes. In Study 1, patrons were randomly assigned either to see a menu that had sustainability labels indicating the degree of environmental impact of each item, or to see a menu without labels. Women who saw the labels were significantly more likely to purchase sustainable foods, whereas men were not influenced by the labels. In Study 2 we targeted one sustainable menu item (a veggie burger) and, in a 2 (sustainability) x 2 (taste) design, varied whether patrons learned that the veggie burger was especially sustainable or especially tasty. Women were significantly more likely to purchase the veggie burger if they learned it was sustainable or tasty, but again, the manipulations had no effect on men. We discuss why women are more likely to change their food choices to eat more sustainably than are men.

Reducing food loss and waste (FLW) is critical for achieving healthy diets from sustainable food systems. Within the United States, 30% to 50% of food produced is lost or wasted. These losses occur throughout multiple stages of the food supply chain from production to consumption. Reducing FLW prevents the waste of land, water, energy, and other resources embedded in food and is therefore essential to improving the sustainability of food systems. Despite the increasing number of studies identifying FLW reduction as a societal imperative, we lack the information needed to assess fully the effectiveness of interventions along the supply chain. In this paper, we synthesize the available literature, data, and methods for estimating the volume of FLW and assessing the full environmental and economic effects of interventions to prevent or reduce FLW in the United States. We describe potential FLW interventions in detail, including policy changes, technological solutions, and changes in practices and behaviors at all stages of the food system from farms to consumers and approaches to conducting economic analyses of the effects of interventions. In summary, this paper comprehensively reviews available information on the causes and consequences of FLW in the United States and lays the groundwork for prioritizing FLW interventions to benefit the environment and stakeholders in the food system.

Reductions in acidic deposition following the 1990 Amendments to the Clean Air Act have led to improvements in the acid/base status of many freshwater bodies in the eastern United States, but such recovery has not been as widespread in Virginia mountain streams. In the current analysis, water chemistry trends are determined for 63 streams within Shenandoah National Park, Virginia, and surrounding national forests, where water samples have been collected on a quarterly basis from 1987 to 2019. Over this timeframe, a majority of the most acid-sensitive streams – those with watersheds underlain by siliciclastic bedrock – have experienced reductions in acid neutralizing capacity (ANC). This outcome, which differs from the modest recovery predicted by earlier modeling studies, is likely due to further depletion of soil base cations and perhaps increases in organic acids. Meanwhile, stream water pH has increased for all watershed bedrock types, averaging between 0.05 and 0.10 pH units per decade. High-flow sampling was conducted at three sites from 1992 to 2019, revealing an assessment of episodic acidification that is more encouraging than that of chronic acidification. For two of these sites, pH during high-flow conditions increased much more rapidly than pH during low-flow conditions. Steep reductions in sulfur deposition over the three decades since the 1990 Amendments have led to a “flushing” of sulfate from shallow soils, which has contributed to the improved acid/base status during episodes of high flow. The findings suggest that continued low acidic deposition rates will lead to further improvements in stream water quality, with the timescales of recovery dependent upon bedrock geology of the watersheds.

Different crops and fertilizer combinations result in different greenhouse gas (GHG) emissions. To investigate GHG emissions among crops with different chemical fertilizer production and use processes, we use a partial life-cycle based greenhouse gas footprint approach to evaluate total GHG emissions, emissions per unit area, and emissions per unit yield of nine crops receiving applications of seven chemical fertilizers for the period 1998 to 2016 in China. Our results show that the life-cycle GHG emissions in China increased by 35% over this 18-year period. Chemical fertilizer use has a greater influence than chemical fertilizer production, as it emitted over half of total GHG emissions. Due to different fertilizer types/uses and cultivated areas, GHG emissions varied among crops. The three main grain crops including rice, wheat, and maize contributed half of the total GHG emissions, mainly due to their larger cultivated areas than other crops. Crops with smaller cultivated areas but larger fertilizer application rates also contributed nonnegligible GHG emissions. For example, vegetable production increased nearly two-fold and accounted for about 20% of total GHG emissions, due to high applications of urea, NPK compound fertilizer, and diammonium phosphate. Fruit crops contributed both much higher GHG emissions and GHG emissions per cultivated area than most other crops, resulting from high application intensities of urea and NPK compound fertilizer. Among the chemical fertilizers, urea generated the greatest GHG emissions (~60% of the total GHG emissions) due not only to its relatively high application across the crops, but also its relatively high GHG emission intensities for both production and application. Finally, we explore potential to mitigate the life-cycle GHG emissions of chemical fertilizers nationally, through varying fertilizer application rates, fertilizer types, and cultivated areas. For example, our scenarios modify the cultivated areas of the three main grain crops, reduce urea and NPK compound fertilizer for fruits and vegetables, and substitute some urea and diammonium phosphate with superphosphate and potassium chloride. Our study highlights the importance of different chemical fertilizer and crop combinations. It can help to mitigate the GHG emissions comprehensively and objectively.

The United States’ legal strategy for addressing climate change in recent years has relied on authority from existing legislation. This has led to measures on a number of different greenhouse gases, notably carbon dioxide, methane and hydrofluorocarbons. However, one greenhouse gas has been largely forgotten: nitrous oxide. Nitrous oxide is the third most abundantly emitted greenhouse gas in the U.S. and worldwide, as well as the largest remaining threat to the stratospheric ozone layer. In addition, the nitrogen atoms in nitrous oxide are part of the highly fluid nitrogen cycle where nitrogen atoms transform readily among different chemical forms, each with a unique environmental and human health impact – a process known as the nitrogen cascade. While the science of the nitrogen cascade has been explored for over a decade, there has been little work on the legal implications of this phenomenon. And yet the nitrogen cascade expands the legal options available for controlling nitrous oxide. This paper studies these options in a U.S. context and explores the environmental and economic impacts of enacting them. We determine that the Clean Air Act, and in particular its broad authority for controlling ozone depleting substances, is the most promising legal pathway for regulating nitrous oxide across all major sources. Invoking such authority could generate significant climate and stratospheric ozone benefits over 2015–2030, equivalent to taking 12 million cars permanently off the road, and 100 million chlorofluorocarbon-laden refrigerators out of service. The economic benefits could sum to over $700 billion over 2015–2030, with every $1.00 spent on abating emissions leading to $4.10 in societal benefits. The bulk of these benefits would come from reductions in other forms of nitrogen pollution such as ammonia and nitrate, highlighting the important and multiple co-benefits that could be achieved by abating nitrous oxide emissions. With the Paris Climate Agreement calling for limiting global temperature increases to “well below” two degrees Celsius, all mitigation opportunities across all sectors need to be considered. This paper suggests that nitrous oxide warrants more attention from policy-makers in the U.S. and around the world.

The excessive use of fertilizer has resulted in serious environmental degradation and a high health cost in China. Much research has focused on the technological innovation to improve fertilizer use efficiency in crop production, but the socioeconomic constraints are at present poorly understood. Here, we find that fertilizer use on a per-area basis sharply decreased with the increase of farm size; surprisingly, the crop yield is higher in large-scale farms compared to that in smallholder farms in China. High labor cost suggests a low machinery level in smallholder farms, which inhibit the application of precise fertilization technologies and management based on scientific knowledge. Meanwhile, the dependence of income from cropland is lower for smallholder farmers who have part-time jobs in urban areas compared to the professional farmers in large-scale farms. Therefore, compared to smallholder farms, large-scale farms are generally more sensitive to the increase of fertilizer price and would reduce their fertilizer use if withdrawing fertilizer subsidies that used to be considered as the key driver of fertilizer overuse. Considering the dominance of smallholder farms in China, increasing farm size should be integrated into the actions such as improving technological innovation and providing better information transfer to achieve the goal of no increase in Chinese fertilizer use.

Nitrogen (N) management presents a sustainability dilemma: N is strongly linked to energy and food production, but excess reactive N causes environmental pollution. The N footprint is an indicator that quantifies reactive N losses to the environment from consumption and production of food and the use of energy. The average per capita N footprint (calculated using the N-Calculator methodology) of ten countries varies from 15 to 47 kg N capita−1 year−1. The major cause of the difference is the protein consumption rates and food production N losses. The food sector dominates all countries’ N footprints. Global connections via trade significantly affect the N footprint in countries that rely on imported foods and feeds. The authors present N footprint reduction strategies (e.g., improve N use efficiency, increase N recycling, reduce food waste, shift dietary choices) and identify knowledge gaps (e.g., the N footprint from nonfood goods and soil N process).

Meeting the food needs of the growing and increasingly affluent human population with the planet’s limited resources is a major challenge of our time. Seen as the preferred approach to global food security issues, ‘sustainable intensification’ is the enhancement of crop yields while minimizing environmental impacts and preserving the ability of future generations to use the land. It is still unclear to what extent sustainable intensification would allow humanity to meet its demand for food commodities. Here we use the footprints for water, nitrogen, carbon and land to quantitatively evaluate resource demands and greenhouse gas (GHG) emissions of future agriculture and investigate whether an increase in these environmental burdens of food production can be avoided under a variety of dietary scenarios. We calculate average footprints of the current diet and find that animal products account for 43–87% of an individual’s environmental burden – compared to 18% of caloric intake and 39% of protein intake. Interestingly, we find that projected improvements in production efficiency would be insufficient to meet future food demand without also increasing the total environmental burden of food production. Transitioning to less impactful diets would in many cases allow production efficiency to keep pace with growth in human demand while minimizing the food system’s environmental burden. This study provides a useful approach for evaluating the attainability of sustainable targets and for better integrating food security and environmental impacts.

Concern over the ecological damage of excess nitrogen has brought increased attention to the role of research institutions and universities in contributing to this problem. Institutions often utilize the concept of the ecological ‘footprint’ to quantify and track nitrogen emissions resulting from their activities and guide plans and commitments to reduce emissions. Often, large-scale changes and commitments to reduce nitrogen footprints are not feasible at small institutions due to monetary and manpower constraints. We partnered with managers in the dining and facilities departments at the Marine Biological Laboratory (MBL), a small research institution in Woods Hole, Massachusetts, to develop five low-effort strategies to address nitrogen emissions at the institution using only resources currently available within those departments. Each proposed strategy achieved emissions reductions in their sector and in the overall nitrogen footprint of the MBL. If all modelled strategies are applied simultaneously, the MBL can achieve a 7.7% decrease in its nitrogen footprint. Managers at MBL considered strategies that required no monetary input most feasible. The intersection of carbon and nitrogen emissions also means the modelled strategies had the co-benefit of reducing the MBL’s carbon footprint, strengthening the argument for applying these strategies. This paper may serve as a model for similar institutions looking to reduce the ecological impact of their activities.

The nitrogen footprint tool (NFT) provides a novel way for communities to understand the environmental impacts of their collective activities and consumption. Reactive nitrogen (Nr; all N species except N2) is created by the Haber–Bosch process for food production and as a by-product of fossil fuel combustion and two natural processes, biological nitrogen fixation and lightning. While it is a vital input for food production, too much Nr has a negative effect on the environment. Calculating the amount of Nr released to the environment as a result of an entity’s resource consumption is the first step in reducing those Nr losses. The nitrogen (N) footprint method has previously taken this approach at the personal and institution scale. In this study, the approach is extended, for the first time, to the spatial patterns of the community nitrogen footprint within a large city, through the integration of diverse geographic information to calculate the N footprint distribution within the City of Baltimore, Maryland, USA. The total N footprint of Baltimore City was ∼19 000 MT N or 30 kg N per capita in 2016, dominated by the food production sector (73%), followed by the energy and transportation sectors (15% combined). There was geographic variability among census block groups’ per capita N footprint within Baltimore City; driven primarily by economic and development factors. Several management scenarios were assessed to better understand what actions may reduce the Baltimore N footprint at the city and community scale over time. The study explored the effect and efficacy of reducing meat consumption based on differences in city consumption patterns, increasing the use of renewable energy sources, and reducing electricity consumption on the city’s total N footprint. The model for the Baltimore City N footprint calculation can be applied to other communities in the United States at the spatial grain of the census block group or any country with this level of data to provide an indicator of nitrogen sustainability.

Ammonia (NH3) released to the atmosphere leads to a cascade of impacts on the environment, yet estimation of NH3 volatilization from cropland soils (VNH3) in a broad spatial scale is still quite uncertain in China. This mainly stems from nonlinear relationships between VNH3 and relevant factors. On the basis of 495 site-years of measurements at 78 sites across Chinese croplands, we developed a nonlinear Bayesian tree regression model to determine how environmental factors modulate the local derivative of VNH3 to nitrogen application rates (Nrate) (VR, %). The VNH3-Nrate relationship was nonlinear. The VR of upland soils and paddy soils depended primarily on local water input and Nrate, respectively. Our model demonstrated good reproductions of VNH3 compared to previous models, i.e., more than 91% of the observed VR variance at sites in China and 79% of those at validation sites outside China. The observed spatial pattern of VNH3 in China agreed well with satellite-based estimates of NH3 column concentrations. The average VRs in China derived from our model were 14.8 ± 2.9% and 11.8 ± 2.0% for upland soils and paddy soils, respectively. The estimated annual NH3 emission in China (3.96 ± 0.76 TgNH3·yr(-1)) was 40% greater than that based on the IPCC Tier 1 guideline.