Agriculture / Food / Nitrogen

^Guo, Yixin, Pan He, Tim D. Searchinger, ..., Xin Zhang, Lin Zhang, and Denise L. Mauzerall+. “Environmental and human health trade-offs in potential Chinese dietary shifts.” One Earth 5 (2022).Abstract
Research shows that dietary shifts toward balanced diets and diets with more plant-based protein provide opportunities to address environmental and health challenges, but the effects on nitrogen pollution, associated air quality related deaths, and land use-associated carbon storage remain unclear. We examine a shift in Chinese diets toward four hypothetical alternative diets and find opportunities to mitigate air pollution and reduce disease burdens. Pairing improved food production techniques with modified dietary practices can benefit health and the environment.
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Guo^, Yixin, Youfan Chen, Timothy D. Searchinger, Mi Zhou^, Da Pan^, ..., and Denise L. Mauzerall+. “Air quality, nitrogen use efficiency and food security in China are improved by cost-effective agricultural nitrogen management.” Nature Food 1 (2020).Abstract
China’s gains in food production over the past four decades have been associated with substantial agricultural nitrogen losses, which contribute to air and water pollution, greenhouse gas emissions and damage to human health. Here, we explore the potential to improve agricultural production practices that simultaneously increase yields while addressing these environmental challenges. We link agronomic research with air quality modelling for an integrated assessment of four improved nitrogen management strategies: improved farm management practices with nitrogen use reductions; machine deep placement of fertilizer; enhanced-efficiency fertilizer use; and improved manure management. We find that simultaneous implementation of the four strategies provides the largest benefits, which include: reductions in PM2.5 concentrations and associated premature deaths; increases in grain yields and grain nitrogen use efficiency; reductions in NO3− leaching and runoff and greenhouse gas emissions. Total benefits of US$30 billion per year exceed the US$18 billion per year in costs. Our findings indicate that policies that improve farmers’ agricultural nitrogen management in China will improve both food security and public health while addressing multiple environmental challenges. Similar increases in attention on agricultural policy around the world are likely to provide large benefits in food security, environmental integrity and public health.
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Kanter, David R, Xin Zhang, Denise L Mauzerall+, Sergey Malyshev, and Elena Shevliakova. “The importance of climate change and nitrogen use efficiency for future nitrous oxide emissions from agriculture.” Environ. Res. Lett. 44, no. 2 (2016).Abstract
Nitrous oxide (N2O) is an important greenhouse gas and ozone depleting substance. Previous projections of agricultural N2O (the dominant anthropogenic source)show emissions changing in tandem, or at a faster rate than changes in nitrogen (N) consumption. However, recent studies suggest that the carbon dioxide (CO2) fertilization effect may increase plant N uptake, which could decrease soil N losses and dampen increases in N2O. To evaluate this hypothesis at a global scale, we use a process-based land model with a coupled carbon-nitrogen cycle to examine how changes in climatic factors, land-use, and N application rates could affect agricultural N2O emissions by 2050. Assuming little improvement in N use efficiency (NUE), the model projects a 24%–31% increase in global agricultural N2O emissions by 2040–2050 depending on the climate scenario—a relatively moderate increase compared to the projected increases in N inputs(42%–44%) and previously published emissions projections(38%–75%). This occurs largely because the CO2 fertilization effect enhances plant N uptake in several regions, which subsequently dampens N2O emissions. And yet, improvements in NUE could still deliver important environmental benefits by 2050: equivalent to 10 Pg CO2 equivalent and 0.6 Tg ozone depletion potential.
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Dalin, Carole, Huanguang Qiu, Naota Hanasaki, Denise L. Mauzerall, and Ignacio Rodriguez-Iturbe. “Balancing water resource conservation and food security in China.” Proceeding of the National Academy of Science (2015).Abstract
China’s economic growth is expected to continue into the next decades, accompanied by sustained urbanization and industrialization. The associated increase in demand for land, water resources, and rich foods will deepen the challenge of sustainably feeding the population and balancing agricultural and environmental policies. We combine a hydrologic model with an economic model to project China’s future food trade patterns and embedded water resources by 2030 and to analyze the effects of targeted irrigation reductions on this system, notably on national agricultural water consumption and food self-sufficiency. We simulate interprovincial and international food trade with a general equilibrium welfare model and a linear programming optimization, and we obtain province-level estimates of commodities’ virtual water content with a hydrologic model. We find that reducing irrigated land in regions highly dependent on scarce river flow and nonrenewable groundwater resources, such as Inner Mongolia and the greater Beijing area, can improve the efficiency of agriculture and trade regarding water resources. It can also avoid significant consumption of irrigation water across China (up to 14.8 km3 /y, reduction by 14%), while incurring relatively small decreases in national food self-sufficiency (e.g., by 3% for wheat). Other researchers found that a national, rather than local, water policy would have similar effects on food production but would only reduce irrigation water consumption by 5%.
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Zhang, Xin, Denise L. Mauzerall+, Eric A. Davidson, David R. Kanter, and Ruohong Cai. “The Economic and Environmental Consequences of Implementing Nitrogen-Efficient Technologies and Management Practices in Agriculture.” Journal of Environmental Quality 44, no. 2 (2015): 312-324.Abstract
Technologies and management practices (TMPs) that reduce the application of nitrogen (N) fertilizer while maintaining crop yields can improve N use efciency (NUE) and are important tools for meeting the dual challenges of increasing food production and reducing N pollution. However, because farmers operate to maximize their profts, incentives to implement TMPs are limited, and TMP implementation will not always reduce N pollution. Therefore, we have developed the NUE Economic and Environmental impact analytical framework (NUE3 ) to examine the economic and environmental consequences of implementing TMPs in agriculture, with a specifc focus on farmer profts, N fertilizer consumption, N losses, and cropland demand. Our analytical analyses show that impact of TMPs on farmers’ economic decision-making and the environment is afected by how TMPs change the yield ceiling and the N fertilization rate at the ceiling and by how the prices of TMPs, fertilizer, and crops vary. Technologies and management practices that increase the yield ceiling appear to create a greater economic incentive for farmers than TMPs that do not but may result in higher N application rates and excess N losses. Nevertheless, the negative environmental impacts of certain TMPs could be avoided if their price stays within a range determined by TMP yield response, fertilizer price, and crop price. We use a case study on corn production in the midwestern United States to demonstrate how NUE3 can be applied to farmers’ economic decision-making and policy analysis. Our NUE3 framework provides an important tool for policymakers to understand how combinations of fertilizer, crop, and TMP prices afect the possibility of achieving win-win outcomes for farmers and the environment.
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Zhang, Xin, Eric A. Davidson, Denise L. Mauzerall, Timothy D. Searchinger, Patrice Dumas, and Ye Shen. “Managing nitrogen for sustainable development.” Nature (2015): 51-59.Abstract
Improvements in nitrogen use efficiency in crop production are critical for addressing the triple challenges of food security, environmental degradation and climate change. Such improvements are conditional not only on technological innovation, but also on socio-economic factors that are at present poorly understood. Here we examine historical patterns of agricultural nitrogen-use efficiency and find a broad range of national approaches to agricultural development and related pollution. We analyse examples of nitrogen use and propose targets, by geographic region and crop type, to meet the 2050 global food demand projected by the Food and Agriculture Organization while also meeting the Sustainable Development Goals pertaining to agriculture recently adopted by the United Nations General Assembly. Furthermore, we discuss socio-economic policies and technological innovations that may help achieve them.
Dalin, Carole, Naota Hanasak, Huanguang Qiu, Denise L. Mauzerall, and Ignacio Rodriguez-Iturbe. “Water resources transfers through Chinese interprovincial and foreign food trade.” Proceedings of the National Academy of Sciences 111, no. 27 (2014).Abstract
China’s water resources are under increasing pressure from socioeconomic development, diet shifts, and climate change. Agriculture still concentrates most of the national water withdrawal. Moreover, a spatial mismatch in water and arable land availability—with abundant agricultural land and little water resources in the north—increases water scarcity and results in virtual water transfers from drier to wetter regions through agricultural trade. We use a general equilibrium welfare model and linear programming optimization to model interprovincial food trade in China. We combine these trade flows with province-level estimates of commodities’ virtual water content to build China’s domestic and foreign virtual water trade network. We observe large variations in agricultural water-use efficiency among provinces. In addition, some provinces particularly rely on irrigation vs. rainwater. We analyze the virtual water flow patterns and the corresponding water savings. We find that this interprovincial network is highly connected and the flow distribution is relatively homogeneous. A significant share of water flows is from international imports (20%), which are dominated by soy (93%). We find that China’s domestic food trade is efficient in terms of rainwater but inefficient regarding irrigation, meaning that dry, irrigation-intensive provinces tend to export to wetter, less irrigation-intensive ones. Importantly, when incorporating foreign imports, China’s soy trade switches from an inefficient system to a particularly efficient one for saving water resources (20 km3 /y irrigation water savings, 41 km3 /y total). Finally, we identify specific provinces (e.g., Inner Mongolia) and products (e.g., corn) that show high potential for irrigation productivity improvements.
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Kanter, David R, Xin Zhang, and Denise L. Mauzerall. “Reducing Nitrogen Pollution while Decreasing Farmers' Costs and Increasing Fertilizer Industry Profits.” Journal of Environmental Quality 44, no. 2 (2014): 325-335.Abstract
Nitrogen (N) pollution is emerging as one of the most important environmental issues of the 21st Century, contributing to air and water pollution, climate change, and stratospheric ozone depletion. With agriculture being the dominant source, we tested whether it is possible to reduce agricultural N pollution in a way that benefits the environment, reduces farmers’ costs, and increases fertilizer industry profitability, thereby creating a “sweet spot” for decision-makers that could significantly increase the viability of improved N management initiatives. Although studies of the economic impacts of improved N management have begun to take into account farmers and the environment, this is the first study to consider the fertilizer industry. Our “sweet spot” hypothesis is evaluated via a cost-benefit analysis of moderate and ambitious N use efficiency targets in U.S. and China corn sectors over the period 2015–2035. We use a blend of publicly available crop and energy price projections, original time-series modeling, and expert elicitation. The results present a mixed picture: although the potential for a “sweet spot” exists in both countries, it is more likely that one occurs in China due to the currently extensive overapplication of fertilizer, which creates a greater potential for farmers and the fertilizer industry to gain economically from improved N management. Nevertheless, the environmental benefits of improving N management consistently dwarf the economic impacts on farmers and the fertilizer industry in both countries, suggesting that viable policy options could include incentives to farmers and the fertilizer industry to increase their support for N management policies.
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Konar, M., Z. Hussein, N. Hanasak, D. L. Mauzerall, and I. Rodriguez-Iturbe. “Virtual water trade flows and savings under climate change.” Hydrol. Earth Syst. Sci. Discuss. 10 (2013): 67-101. Publisher's VersionAbstract
The international trade of food commodities links water and food systems, with important implications for both water and food security. The embodied water resources associated with food trade are referred to as “virtual water trade”. We present the first 5 study of the impact of climate change on global virtual water trade flows and associated savings for the year 2030. In order to project virtual water trade under climate change, it is essential to obtain projections of both bilateral crop trade and the wateruse efficiency of crops in each country of production. We use the Global Trade Analysis Project (GTAP) to estimate bilateral crop trade flows under changes in agricultural pro10 ductivity. We use the H08 global hydrologic model to estimate the water-use efficiency of each crop in each country of production and to transform crop flows into virtual water flows. We find that the total volume of virtual water trade is likely to go down under climate change. However, the staple food trade is projected to save more water across most climate impact scenarios, largely because the wheat trade re-organizes into a 15 more water-efficient structure. These findings indicate that trade may be an adaptation measure to climate change with ramifications for policy.
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Kanter, David, Denise L. Mauzerall+, A. R. Ravishankara, John S. Daniel, Robert W. Portmann, Peter M. Grabiel, William R. Moomaw, and James N. Galloway. “A post-Kyoto partner: Considering the stratospheric ozone regime as a tool to manage nitrous oxide.” Proceedings of the National Academy of Sciences (2013).Abstract
Nitrous oxide (N2O) is the largest known remaining anthropogenic threat to the stratospheric ozone layer. However, it is currently only regulated under the 1997 Kyoto Protocol because of its simultaneous ability to warm the climate. The threat N2O poses to the stratospheric ozone layer, coupled with the uncertain future of the international climate regime, motivates our exploration of issues that could be relevant to the Parties to the ozone regime (the 1985 Vienna Convention and its 1987 Montreal Protocol) should they decide to take measures to manage N2O in the future. There are clear legal avenues to regulate N2O under the ozone regime as well as several ways to share authority with the existing and future international climate treaties. N2O mitigation strategies exist to address the most significant anthropogenic sources, including agriculture, where behavioral practices and new technologies could contribute significantly to reducing emissions. Existing policies managing N2O and other forms of reactive nitrogen could be harnessed and built on by the ozone regime to implement N2O controls. There are several challenges and potential cobenefits to N2O control which we discuss here: food security, equity, and implications of the nitrogen cascade. The possible inclusion of N2O in the ozone regime need not be viewed as a sign of failure of the United Nations Framework Convention on Climate Change to adequately deal with climate change. Rather, it could represent an additional valuable tool in sustainable development diplomacy
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Avnery, Shiri, Denise L. Mauzeral+l, and Arlene M. Fiore. “Increasing global agricultural production by reducing ozone damages via methane emission controls and ozoneresistant cultivar selection.” Global Change Biology 19 (2013): 1285-1299.Abstract
Meeting the projected 50% increase in global grain demand by 2030 without further environmental degradation poses a major challenge for agricultural production. Because surface ozone (O3) has a significant negative impact on crop yields, one way to increase future production is to reduce O3-induced agricultural losses. We present two strategies whereby O3 damage to crops may be reduced. We first examine the potential benefits of an O3 mitigation strategy motivated by climate change goals: gradual emission reductions of methane (CH4), an important greenhouse gas and tropospheric O3 precursor that has not yet been targeted for O3 pollution abatement. Our second strategy focuses on adapting crops to O3 exposure by selecting cultivars with demonstrated O3 resistance. We find that the CH4 reductions considered would increase global production of soybean, maize, and wheat by 23–102 Mt in 2030 – the equivalent of a ~2–8% increase in year 2000 production worth $3.5–15 billion worldwide (USD2000), increasing the cost effectiveness of this CH4 mitigation policy. Choosing crop varieties with O3 resistance (relative to median-sensitivity cultivars) could improve global agricultural production in 2030 by over 140 Mt, the equivalent of a 12% increase in 2000 production worth ~$22 billion. Benefits are dominated by improvements for wheat in South Asia, where O3-induced crop losses would otherwise be severe. Combining the two strategies generates benefits that are less than fully additive, given the nature of O3 effects on crops. Our results demonstrate the significant potential to sustainably improve global agricultural production by decreasing O3-induced reductions in crop yields.
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Robertson, GP, TW Bruulsema, R Gehl, D Kanter, DL Mauzerall, A Rotz, and C. Williams. “Climate-Nitrogen Interactions in Agriculture.” In The Role of Nitrogen in Climate Change and the Impacts of Nitrogen-Climate Interactions on Terrestrial and Aquatic Ecosystems, Agriculture, and Human Health in the United States. A Technical Report Submitted to the US National Climate Assessment. Falmouth, MA: North American Nitrogen Center of the International Nitrogen Initiative (NANC-INI), Woods Hole Research Center, 2012. Publisher's Version Full Text PDF
Avnery, Shiri, Denise L. Mauzerall+, Junfeng Liu, and Larry W. Horowitz. “Global Crop Yield Reductions due to Surface Ozone Exposure: 2. Year 2030 Potential Crop Production Losses and Economic Damage under Two Scenarios of O3 Pollution.” Atmospheric Environment 45 (2011): 2297-2309.Abstract
We examine the potential global risk of increasing surface ozone (O3) exposure to three key staple crops (soybean, maize, and wheat) in the near future (year 2030) according to two trajectories of O3 pollution: the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) A2 and B1 storylines, which represent upper- and lower-boundary projections, respectively, of most O3 precursor emissions in 2030. We use simulated hourly O3 concentrations from the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2), satellite-derived datasets of agricultural production, and field-based concentration:response relationships to calculate crop yield reductions resulting from O3 exposure. We then calculate the associated crop production losses and their economic value. We compare our results to the estimated impact of O3 on global agriculture in the year 2000, which we assessed in our companion paper [Avnery et al., 2011]. In the A2 scenario we find global year 2030 yield loss of wheat due to O3 exposure ranges from 5.4 to 26% (a further reduction in yield of þ1.5e10% from year 2000 values), 15e19% for soybean (reduction of þ0.9e11%), and 4.4e8.7% for maize (reduction of þ2.1e3.2%) depending on the metric used, with total global agricultural losses worth $17e35 billion USD2000 annually (an increase of þ$6e17 billion in losses from 2000). Under the B1 scenario, we project less severe but still substantial reductions in yields in 2030: 4.0e17% for wheat (a further decrease in yield of þ0.1e1.8% from 2000), 9.5e15% for soybean (decrease of þ0.7e1.0%), and 2.5e6.0% for maize (decrease of þ 0.3e0.5%), with total losses worth $12e21 billion annually (an increase of þ$1e3 billion in losses from 2000). Because our analysis uses crop data from the year 2000, which likely underestimates agricultural production in 2030 due to the need to feed a population increasing from approximately 6 to 8 billion people between 2000 and 2030, our calculations of crop production and economic losses are highly conservative. Our results suggest that O3 pollution poses a growing threat to global food security even under an optimistic scenario of future ozone precursor emissions. Further efforts to reduce surface O3 concentrations thus provide an excellent opportunity to increase global grain yields without the environmental degradation associated with additional fertilizer application or land cultivation.
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Avnery, Shiri, Denise L. Mauzerall+, Junfeng Liu, and Larry W. Horowitz. “Global Crop Yield Reductions due to Surface Ozone Exposure: 1. Year 2000 Crop Production Losses and Economic Damage.” Atmospheric Environment 45 (2011): 2284-2296.Abstract
Exposure to elevated concentrations of surface ozone (O3) causes substantial reductions in the agricultural yields of many crops. As emissions of O3 precursors rise in many parts of the world over the next few decades, yield reductions from O3 exposure appear likely to increase the challenges of feeding a global population projected to grow from 6 to 9 billion between 2000 and 2050. This study estimates year 2000 global yield reductions of three key staple crops (soybean, maize, and wheat) due to surface ozone exposure using hourly O3 concentrations simulated by the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2). We calculate crop losses according to two metrics of ozone exposure e seasonal daytime (08:00e19:59) mean O3 (M12) and accumulated O3 above a threshold of 40 ppbv (AOT40) e and predict crop yield losses using crop-specific O3 concentration:response functions established by field studies. Our results indicate that year 2000 O3-induced global yield reductions ranged, depending on the metric used, from 8.5e14% for soybean, 3.9e15% for wheat, and 2.2e5.5% for maize. Global crop production losses totaled 79e121 million metric tons, worth $11e18 billion annually (USD2000). Our calculated yield reductions agree well with previous estimates, providing further evidence that yields of major crops across the globe are already being substantially reduced by exposure to surface ozone e a risk that will grow unless O3-precursor emissions are curbed in the future or crop cultivars are developed and utilized that are resistant to O3.
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Wang, X., and D. L. Mauzerall. “Characterizing Distributions of Surface Ozone and its Impact on Grain Production in China, Japan and South Korea: 1990 and 2020.” Atmospheric Environment 38 (2004): 4383-4402.Abstract
Using an integrated assessment approach, we evaluate the impact that surface O3 in East Asia had on agricultural production in 1990 and is projected to have in 2020. We also examine the effect that emission controls and the enforcement of environmental standards could have in increasing grain production in China. We find that given projected increases in O3 concentrations in the region, East Asian countries are presently on the cusp of substantial reductions in grain production. Our conservative estimates, based on 7- and 12-h mean (M7 or M12) exposure indices, show that due to O3 concentrations in 1990 China, Japan and South Korea lost 1–9% of their yield of wheat, rice and corn and 23–27% of their yield of soybeans, with an associated value of 1990US$ 3.5, 1.2 and 0.24 billion, respectively. In 2020, assuming no change in agricultural production practices and again using M7 and M12 exposure indices, grain loss due to increased levels of O3 pollution is projected to increase to 2–16% for wheat, rice and corn and 28–35% for soybeans; the associated economic costs are expected to increase by 82%, 33%, and 67% in 2020 over 1990 for China, Japan and South Korea, respectively. For most crops, the yield losses in 1990 based on SUM06 or W126 exposure indices are lower than yield losses estimated using M7 or M12 exposure indices in China and Japan but higher in South Korea; in 2020, the yield losses based on SUM06 or W126 exposure indices are substantially higher for all crops in all three countries. This is primarily due to the nature of the cumulative indices which weight elevated values of O3 more heavily than lower values. Chinese compliance with its ambient O3 standard in 1990 would have had a limited effect in reducing the grain yield loss caused by O3 exposure, resulting in only US$ 0.2 billion of additional grain revenues, but in 2020 compliance could reduce the yield loss by one third and lead to an increase of US$ 2.6 (M7 or M12) –27 (SUM06) billion in grain revenues. We conclude that East Asian countries may have tremendous losses of crop yields in the near future due to projected increases in O3 concentrations. They likely could achieve substantial increases in future agricultural production through reduction of surface O3 concentrations and/or use of O3 resistant crop cultivars. r 2004 Elsevier Ltd. All rights reserved.
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Mauzerall, Denise L., and Xiaoping Wang. “Protecting Agricultural Crops from the Effects of Tropospheric Ozone Exposure: Reconciling Science and Standard Setting in the United States, Europe and Asia.” Annual Review of Energy and the Environment 26 (2001): 237-268.Abstract
Ozone (O3) is well documented as the air pollutant most damaging to agricultural crops and other plants. Most crops in developed countries are grown in summer when O3 concentrations are elevated and frequently are sufficiently high to reduce yields. This article examines the difficulties in scientifically determining the reduction in yield that results from the exposure of agricultural crops to surface O3 and then transforming that knowledge into efficient and effective regulatory standards. The different approaches taken by the United States and Europe in addressing this issue as well as the few studies that have been conducted to date in developing countries are examined and summarized. Extensive research was conducted in the United States during the 1980s but has not been continued. During the 1990s, the European community forged ahead with scientific research and innovative proposals for air-quality standards. These efforts included the development of a “critical level” (CL) for O3 based on a cumulative exposure above a cutoff concentration below which only an acceptable level of harm is incurred. Current research focuses on estimating O3 dosage to plants and incorporating this metric into regulatory standards. The US regulatory community can learn from current European scientific research and regulatory strategies, which argue strongly for a separate secondary standard for O3 to protect vegetation. Increasing impacts of O3 on crops are likely in developing countries as they continue to industrialize and their emissions of air pollutants increase. More research is needed on surface O3 concentrations in developing countries, on their projected increase, and on the sensitivity that crop cultivars used in developing countries have to O3. The threat of reduced agricultural yields due to increasing O3 concentrations may encourage developing countries to increase their energy efficiency and to use different energy sources. This could simultaneously achieve a local benefit through improved regional air quality and a global benefit through a reduction in the emission of greenhouse gases.
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