Agriculture

Snapshot

Category Description

Agriculture is crucial to sustaining life, but agricultural productivity has often come at the expense of agricultural inputs, such as land, water, and minerals (Alexandratos & Bruinsma, 2012). Sustainable farming and ranching thus depend on better and more efficient use of resources to break this link. Fertilizers rich in nitrogen support plant growth and are thus vital to the agricultural sector. (Zhang et al., 2015, p. 51). Nitrogen pollution, however, has the potential to cause widespread damage if managed inadequately (Bodirsky et al., 2014). The EPI uses one indicator to track nitrogen management as a measure of environmental performance.

Indicator Included

  1. Sustainable nitrogen management index (SNMI). As a gauge of efficiency, the SNMI indicator uses nitrogen use efficiency (NUE) and crop yield to measure the environmental performance of agricultural production (Zhang & Davidson, 2016).
Agriculture Indicators
Sustainable nitrogen management index unitless

Category Overview

Agriculture, while vital to our quality of life, can be harmful to the environment when poorly managed. The world population is expected to increase to over nine billion by 2050 (World Bank, 2017b). As a result, food security has emerged as a front-burner issue. To feed a growing population, the Food and Agriculture Organization of the United Nations (FAO) estimates food production will need to increase by 60% by 2050 (Food and Agriculture Organization, 2016, p. 1). Improving agricultural practices can help protect the environment, public health, and communities. Sustainable agriculture enables food production without compromising the needs of future generations (World Bank, 2017b).

Food security has become a top-tier global issue. One of the challenges of sustainable agriculture centers on using fertilizer efficiently to grow crops without polluting the environment. Unsustainable agricultural practices have substantial, negative environmental impacts (Food and Agriculture Organization, 2016, p. 1). Significant issues facing the agricultural sector today include a loss of arable land for crop production and a loss crop diversity. Over the past 40 years, over 30% of arable land globally has been degraded (Milman, 2015). Industrialized agricultural practices have also led to higher levels of monocultures because it is more economically efficient to produce large quantities of the same type of crop (Food and Agriculture Organization of the United Nations, 2011).

Agriculture intersects with a number of other environmental issues addressed in this report. Within the context of nutrient pollution, however, agriculture poses a distinct threat (Rockström et al., 2009b). Over the past century, massive amounts of both nitrogen and phosphorus have entered into agricultural practices (R. DeFries et al., 2015, p. 238). Adding nutrients – like nitrogen and phosphorous – to the soil allows for an increase in agricultural output. These additions also create substantial costs to the environment, e.g., groundwater contamination, runoff of excess fertilizer that damages water quality, nitrous oxide emissions, degradation of habitat for biodiversity, and fragmentation of economic and social conditions in rural communities (R. DeFries et al., 2015, p. 238)World Bank, 2017b). Nitrogen pollution, therefore, has the potential to cause extensive damages if not sustainably managed (Bodirsky et al., 2014).

The SNMI indicator tracks nitrogen management to assess how well a country uses fertilizer for efficient crop production. We use nitrogen management is a proxy for phosphorus fertilizer management, as both nitrogen and phosphorus are supplied in fertilizers.

Environmental: The agriculture sector’s impact on the environment varies based on the farming practices employed. Excess nitrogen runoff can cause algal blooms, loss of oxygen from the water, and death of aquatic animals (Sutton et al., 2013, p. 32). Some of the most well-known examples of dead zones are in the Gulf of Mexico and the Chesapeake Bay (National Public Radio, 2017). Map 14–1 depicts where dead zones have been observed worldwide.


Map 14-1
Map 14-1. Global map of dead zones.
Note: The black points are observed sites of dead zones, although the size of those dead zones is not known.
Source: The Earth Observatory at NASA,
https://earthobservatory.nasa.gov/IOTD/view.php?id=44677.

Nitrogen fertilizers also produce greenhouse gas emissions in the form of nitrous oxide (N2O). Nitrous oxides are also released when excess nitrogen fertilizer is broken down by soil bacteria. These gases are about 300 times more potent than carbon dioxide (CO2) as greenhouse gases (GHGs) (Sutton et al., 2013, p. ix). The manufacturing of reactive nitrogen is also an energy intensive process, estimated to account for about 2% of the world’s energy use (Sutton et al., 2013, p. 8).

Social: Unsustainable agricultural practices are one of the most significant causes of food scarcity. According to the UN, almost 800 million people globally are undernourished, and by 2050 that number is expected to increase by an additional two billion people (United Nations News Centre, 2016). To alleviate undernourishment and hunger, agricultural yields must increase. In areas where with minimal amounts of fertilizer use, adding nitrogen to the soil is unlikely to cause large amounts of pollution (Zhang, 2017, p. 322). However, when more nitrogen fertilizer is applied “in regions that have high nitrogen-fertilization rates […] most of the added nitrogen is lost as air and water pollution” (Zhang, 2017, p. 322).

Economic: Agriculture plays an important role in economic development. According to the UN, the agricultural sector is the largest employer in the world and provides livelihoods for approximately 40% of the world’s population (United Nations, n.d.). The value added of world’s agricultural production was estimated at US$3.18 trillion in 2016 (World Bank, 2017a).

Global Impact

Nitrogen supports productivity and sustains life. While some reactive nitrogen occurs naturally, anthropogenic inputs of reactive nitrogen are now double natural levels (Holtgrieve et al., 2011). Human influence on the nitrogen cycle has exceeded the natural bounds for ecosystem functions globally (Rockström et al., 2009a). Many factors contribute to this proliferation in nitrogen pollution, but agriculture is the most prevalent source of reactive nitrogen (Rockström et al., 2009a).

The industrialization of agriculture has allowed for significant increases in crop yields over the past century (R. DeFries et al., 2015, p. 238). The use of synthetic fertilizers became widespread in the 1900s through the Haber-Bosch process, an energy-intensive method that synthesizes nitrogen compounds from the atmosphere (Sutton et al., 2013, p. 4). The Haber-Bosch process has permitted the development of both more-varied and richer diets (Sutton et al., 2013, p. 4). To date, no region has been able to increase agricultural growth without increasing fertilizer use as well (World Bank, 2017b, p. 27). Now, more than half of the world population is dependent on crops grown with nitrogen-rich fertilizers (Zhang et al., 2015, p. 51). Agricultural productivity has substantially increased, but it has come at the expense of sustainability and equitable development (Alexandratos & Bruinsma, 2012).

United Nations Sustainable Development Goal (SDG) 2 aims to address the challenges of global food security by making agriculture more sustainable.

Goal 2: End hunger, achieve food security and improved nutrition and promote sustainable agriculture

Goal 2, Target 4: By 2030, ensure sustainable food production systems and implement resilient agricultural practices that increase productivity and production, that help maintain ecosystems, that strengthen capacity for adaptation to climate change, extreme weather, drought, flooding and other disasters and that progressively improve land and soil quality

Goal 2, Target 5: By 2020, maintain the genetic diversity of seeds, cultivated plants and farmed and domesticated animals and their related wild species, including through soundly managed and diversified seed and plant banks at the national, regional and international levels, and promote access to and fair and equitable sharing of benefits arising from the utilization of genetic resources and associated traditional knowledge, as internationally agreed

Goal 2, Target a: Increase investment, including through enhanced international coöperation, in rural infrastructure, agricultural research and extension services, technology development and plant and livestock gene banks in order to enhance agricultural productive capacity in developing countries, in particular least developed countries

Goal 2, Target b: Correct and prevent trade restrictions and distortions in world agricultural markets, including through the parallel elimination of all forms of agricultural export subsidies and all export measures with equivalent effect, in accordance with the mandate of the Doha Development Round

International Organizations

Consultative Group on International Agricultural Research (CGIAR): CGIAR is a global research partnership working for “[a] world free of poverty, hunger and environmental degradation.” http://www.cgiar.org/.

Food and Agriculture Organization of the United Nations (FAO): FAO is an intergovernmental organization working to make agricultural production more productive and sustainable. The Organization is comprised of 194 member states, two associate members, and one member organization – The European Union. http://www.fao.org/home/en/.

Global Partnership on Nutrient Management (GPNM): This partnership was launched with governments, scientists, policymakers, and international organizations to research and promote effective nutrient reduction strategies in agriculture.  http://web.unep.org/gpa/what-we-do/global-partnership-nutrient-management.

United Nations Environment Programme (UNEP): The UNEP is the agency within the UN coördinating and implementing environmental actions. As one of their many duties, UNEP is tasked with helping to implement the SDGs. https://www.unenvironment.org/.

World Bank Group: The World Bank Group is a leading investor in agriculture globally, working with countries and providing infrastructure and resources to the food and agriculture sector.  http://www.worldbank.org/en/topic/agriculture.

World Trade Organization (WTO):  One of the WTO’s international treaties, the Agreement on Agriculture, aims to limit barriers to trade in agriculture and to open agricultural market access. https://www.wto.org/english/tratop_e/agric_e/agric_e.htm.

Multilateral Efforts

Convention on Biological Diversity Aichi Target 8: By 2020, pollution, including from excess nutrients, has been brought to levels that are not detrimental to ecosystem function and biodiversity. https://www.cbd.int/sp/targets/default.shtml.

Global Environmental Facility (GEF): Established during the 1992 Rio Earth Summit, the GEF assists with climate change adaptation, working on issues spanning sustainable agriculture, food security, and land use. https://www.thegef.org/.

International Fund for Agricultural Development (IFAD): The IFAD is a specialized agency of the UN that funds agricultural development projects in areas that depend largely on agriculture. https://www.ifad.org/.

International Plant Protection Convention (IPPC): The IPPC is a multilateral treaty of the FAO that aims to protect, preserve, and extend plant biodiversity for food and agriculture. https://www.ippc.int/en/.

International Treaty on Plant Genetic Resources for Food and Agriculture (IT PGRFA): Adopted in 2001, the objectives of this legally binding treaty incorporate the conservation and sustainable use of plant genetic resources for food and agriculture. http://www.fao.org/plant-treaty/en/.

UN Framework Convention on Climate Change (UNFCC): The UNFCC includes the promotion of sustainable agriculture and climate change mitigation through agricultural adaptation technologies. http://unfccc.int/land_use_and_climate_change/agriculture/items/8793.php.

UN’s Oceans Compact Goal 1, Target 1: Reducing pollutants from sea and land-based activities, including gas and oil extraction, marine debris, harmful substances and nutrients from wastewater, industrial and agricultural runoff entering the world’s oceans. http://www.un.org/depts/los/ocean_compact/SGs%20OCEAN%20COMPACT%202012-EN-low%20res.pdf.

World Food Program (WFP): The WFP is a branch of the UN that aims to prevent hunger and deliver food aid. http://www1.wfp.org/.

Measurement

When assessing sustainable agriculture, data are needed for a number of systems. World Resources Institute’s (WRI) Indicators of Sustainable Agriculture: A Scoping Analysis report evaluated research that has studied different agricultural systems (Reytar, Hanson, & Henninger, 2014). Surveying past and potential measurements, WRI identified five areas in which agricultural indicators are needed (Reytar et al., 2014, pp. 10–11):

  1. Water. Indicators that best reflect agricultural pressure on water resource use.
  2. Climate Change. Indicators that best capture the impact of agriculture on GHG emissions.
  3. Land Conversion. Indicators that best capture the conversion of natural land into agricultural land.
  4. Soil Health. Indicators that best reflect the impact of agriculture on soil health and productivity.
  5. Pollution. Indicators that best capture the environmental degradation caused by agricultural nutrient inputs, agricultural pesticides, and other pollutants.

WRI emphasizes the need to improve data quality and scope, despite the number of studies and datasets that address some of these indicator areas (Reytar et al., 2014). These data issues – combined with countries’ resource limitations – lead to numerous methodological problems. The WRI use seven specific criteria to evaluate agriculture indicators, but two of them illustrate the largest gaps in the measurement of agricultural sustainability: the lack of globally available and regularly collected data (Reytar et al., 2014, pp. 10, 12–16). Improving existing indicators and developing new ones to address these gaps is vital to ensure that policymakers can compare their country’s performance against other nations and against historic benchmarks. An EU handbook highlights the importance of broadening discussions of nutrients to explicitly include phosphorus in addition to nitrogen to capture more nuance in the measurement of agricultural pollution (Eurostat & Organisation for Economic Coöperation and Development, 2013, p. 25). 

Indicators that measure the environmental impacts of agriculture are an important tool to gauge global efforts towards a sustainable food future. We identify the SNMI indicator as the best representation of environmental performance given existing limitations with consistent, comprehensive data on sustainable agriculture practice. The SNMI measures how much excess nitrogen enters the environment where it could have negative environmental effects. While the EPI’s analysis on agricultural sustainability provides a starting point to understand fertilizer use in a country, it does not provide countries with data at the level of detail required to inform policy action. Policymakers should find ways to incorporate local data into their decisionmaking.  

Box 14-1. Connections to other Chapters. Environmental issues associated with nitrogen pollution.

Agriculture is a significant cause of deforestation, climate change, and water degradation. The management challenges that arise from nitrogen use are particularly difficult due to the ways it interacts with other elements (Sutton et al., 2013). The different chemical forms of nitrogen are addressed in part by other Chapters in the EPI, including Climate & Energy, Air Pollution, Forests, and Water & Sanitation. Examples of excess nitrogen’s impact on the environment in other issue indicators include:

Climate & Energy. Nitrous oxides are potent GHGs that are about 300 times the global warming potential of CO2 (Sutton et al., 2011).

Biodiversity. Excess nitrogen in aquatic systems can lead to algae blooms. When algae decompose, they consume oxygen in the water column, which can kill other aquatic species. (Galloway et al., 2003).

Air Quality and Air Pollution. NOx is a precursor to ozone, which can have harmful effects on humans, animals, and plants (Royal Society (Great Britain) & Fowler, 2008).

Forests. Excess NOx in the atmosphere forms acid rain, which can damage tree roots and make it more difficult for trees to take up nutrients  (Sutton et al., 2011).

While the chapters are analyzed separately, their relationships to one another should be understood, and addressed, collectively. In the context of this issue category, sustainable nitrogen management is essential to support plant growth, but has the potential to cause widespread damage if managed inadequately (Bodirsky et al., 2014).

Sustainable Nitrogen Management Index

Indicator Background

The 2018 EPI uses the SNMI as a proxy of agricultural drivers of environmental damage. This novel metric, proposed by Zhang and Davidson (2016), seeks to balance the two elements of sustainable agriculture. First, countries are assessed by their NUE, which is a measure of the portion of nitrogen input harvested in crops (Zhang et al., 2015). Second, countries are then assessed on nitrogen yield, or the mass of nitrogen harvested per unit of land.

Ideally, a country should have optimal NUE to avoid excess inputs of fertilizer into the environment, while maintaining yields that meets the needs of its people. The SNMI is a composite score of how far away a country is from its ideal point of perfect NUE and yield, as depicted in Figure 14–1. It is based on how far away a country falls from the reference point, which is defined as a certain yield target. Zhang and Davidson (2016, p. 2)define this reference yield level as 90 kg N/ha/yr, based on the FAO’s estimate of the “required nitrogen yield, averaged globally, to meet 2050 crop production targets without expanding the current crop land” (Alexandratos & Bruinsma, 2012; Zhang & Davidson, 2016, p. 2).


Figure 14-1
Figure 14-1. SNMI, which is based on NUE and N yield.
Note: The reference point is depicted as a star icon.
Source: Zhang et al.

 

Data Description

Our metric is focused specifically on agriculture disruption of the nitrogen cycle. Data are available for 147 countries for 2010 and are provided by Dr. Xin Zhang and her team at the University of Maryland Center for Environmental Science. Zhang’s team has data over the period of 1961–2011, but the SNMI has only been calculated for 2010 thus far. NUE and yield are computed using country-level data obtained by Zhang et al. from the Food and Agriculture Organization’s Corporate Statistical Database (FAOSTAT) and published in Nature (Zhang et al., 2015). The SNMI is the Euclidean distance of a country’s normalized NUE and yield from an ideal point. The methodology for SNMI is described in further detail in Zhang and Davidson (2016).


Figure 14-2
Figure 14-2. Historical nitrogen trends of seven countries showing yield compared to NUE over time.
Source: Zhang et al.

 

As shown in Figure 14-2, the historical performance of countries should trend toward the ideal point in the SNMI framework. Over four decades, Brazil and the United States of America (USA) have made remarkable progress in increasing yields, with the USA exceeding the FAO’s simple baseline of 90 kg N/ha/yr over two decades ago. However, there has been very little change in NUE over this period for these two breadbaskets. In contrast, France has managed to increase both yields and NUE, with the largest gains in NUE occurring over the recent past. The rest of the developing world shows less progress in yields and worrying declines in NUE. The challenge of sustainable agriculture is to bend these trajectories toward the ideal point.

Limitations

SNMI is a proxy for agricultural environmental performance and only tangentially measures the environmental problems associated with agriculture. Certain limitations arise because countries can have the same score for very different reasons. For example, a country can be in nitrogen excess and deficiency at the same time (Zhang & Davidson, 2016). Regions also have varying amounts of nutrients found in their soils and thus require different amounts of fertilizer to support agricultural yields. Rather than using FAO’s 2050 yield target of 90 kg N/ha/yr (Alexandratos & Bruinsma, 2012; Zhang & Davidson, 2016, p. 2), country-specific benchmarks are needed for normalizing nitrogen yield (Reytar et al., 2014, p. 5).

The SNMI encompasses only part of the information necessary to capture country-specific agricultural management practices resources (Reytar et al., 2014). The indicator does not consider the impact from international trade. If international trade across croplands was improved, nitrogen pollution has the potential to decrease (Zhang, 2017, p. 322). This fact also illustrates the need to account for the impacts of global trade in nitrogen emissions, as export- and import-oriented food production models influence the distribution of nitrogen pollution (Lassaletta et al., 2016). Using research by Oita et al. (2016), the SDG Index includes a metric that captures the nitrogen pollution from a country’s net imports (Sachs, Schmidt-Traub, Kroll, Durand-Delacre, & Teksoz, 2017, p. 26). This metric accounts for the environmental impacts of the food consumed, but not produced domestically by each country (Oita et al., 2016, p. 111; Sachs et al., 2017, p. 26), while the SNMI is based only on production.

Additional limitations in our dataset arise because the SNMI is only comprehensively available for the year 2010 thus far and only encompasses a limited number of countries. Further, the straight-line distance between the sets of yield & NUE for equivalent scores, as represented by the iso-performance curves in Figure 14–2, illustrate the path countries should follow to improve overall performance. Top performers would achieve high yields along with efficient nitrogen use. The target for nitrogen yield in each country may differ from the FAO’s general standard of 90 kg N/ha/yr. More research is needed to set country-specific targets. Finally, while the FAOSTAT database provides historical records of nitrogen fertilizer use, it does not provide a breakdown of how the fertilizers have been used for pastures versus different crop types (Zhang et al., 2015). SNMI, while still a work in progress, represents an intermediate step toward measuring sustainable agricultural productivity globally.

Results

Global Trends

Table 14–1. Global Trends in Sustainable Nitrogen Management.
Note: Metric is an index that measures the environmental performance of a country’s agricultural production using a benchmark that describes perfect nitrogen use efficiency and high crop yields. Current refers to data from 2011, and Baseline refers to historic data from 2001.
Indicator Metric Score
  Baseline Current Baseline Current
Sustainable Nitrogen Management Index 0.61 0.57 44.0 47.7

Globally, sustainable nitrogen management has improved very slightly, with the global indicator score increasing by 3.7 points – see Table 14–1. The 6.5% decrease in the metric score (from 0.61 to 0.57) reflects a smaller difference between actual and ideal nitrogen efficiency and yields, demonstrating global progress on this issue. However, these small score improvements reflect increasing yields rather than improvements in efficiency. An index value of 0 indicates that the nitrogen use efficiency is 1 (i.e., all nitrogen added to the soil is removed in the food) and that agricultural yields are above a certain reference point, chosen to be 90 kg N/ha/yr in this index (Zhang & Davidson, 2016, pp. 1–2). Nitrogen use efficiencies can increase above 1 when more nitrogen is being removed from the soil than added. In general, net nitrogen removal reduces the fertility of the soil; however, Zhang & Davidson argue that this also presents an opportunity to add fertilizer to produce higher yields without causing substantial nitrogen pollution (Zhang et al., 2015, p. 54).

Our reference yield of 90 kg N/ha/yr reflects the “required nitrogen yield, averaged globally, to meet 2050 crop production targets without expanding the current crop land” (Alexandratos & Bruinsma, 2012; Zhang & Davidson, 2016, p. 2). To produce these yields while staying within sustainable emission limits for nitrogen pollution, nitrogen use efficiency must to increase by roughly 0.3 by 2050 (Zhang et al., 2015, p. 56). Progress from all countries in all regions will help achieve 2050 goals (Zhang et al., 2015, pp. 55–56). In the United States and European Union, the agriculture sector will need to continue trends of increasing yields while decreasing nitrogen inputs to increase efficiency (Zhang et al., 2015, p. 56). Transitioning economies, such as China and India, will need to make sharp increases in efficiency to reduce pollution and begin to move in the direction of the developed world (Zhang et al., 2015, p. 56).

There are many potential pathways for improving nitrogen efficiency and increasing crop yields. Carefully increasing fertilizer use in places with low fertilizer usage, such as Sub-Saharan Africa, can raise yields with relatively low nitrogen pollution (Zhang, 2017, pp. 322–323). On a broader scale, increasing fertilizer use in the regions where it would have the greatest impact, and reducing it where it does not, may maintain yields while reducing nitrogen pollution by as much as 41% over a 15-year period (Mueller et al., 2017, p. 251). Technological improvements can also help produce higher yields without increasing nitrogen pollution. The development of crop varieties that can produce high yields in low-nitrogen soils is one example (Hirel, Le Gouis, Ney, & Gallais, 2007, pp. 2369–2370; Moll, Kamprath, & Jackson, 1982, p. 562). Finally, removing subsidies that create perverse incentives to over-fertilize can encourage sustainable nitrogen management (Zhang, 2017, p. 323; Zhang et al., 2015, pp. 52–54).

Efforts to sustainably manage nitrogen have produced mixed results. Figure 14–2 highlights the progress made by a variety of countries thus far. Trends in France, the United States, and Brazil show constant or increasing trends nitrogen efficiency, even in the face of increasing agricultural yields. China’s decreasing trend nitrogen use efficiency, on the other hand, may be cause for concern. Developing strategies to improve sustainability in large developing countries is becoming increasingly important. China and India, for example, create more than half of the world’s nitrogen pollution, compared to less than 15% caused by the United States and Europe combined (Zhang et al., 2015, p. 55).

Leaders & Laggards

Table 14-2. Leaders in sustainable nitrogen management.
Rank Country Score
1 Paraguay 75.77
2 United States of America 72.38
3 Austria 71.34
4 Argentina 70.69
5 Hungary 69.15
6 France 67.77
7 Denmark 67.02
8 Uruguay 62.38
9 Czech Republic 62.17
10 Lithuania 62.01
Table 14-3. Laggards in sustainable nitrogen management.
Rank Country Score
171 Costa Rica 6.04
172 Georgia 5.7
173 Singapore 4.59
174 Mauritius 4.51
175 Saint Vincent and the Grenadines 3.22
176 Grenada 0.76
177 Dominica 0
177 Saint Lucia 0
177 Trinidad and Tobago 0
177 United Arab Emirates 0

The top performers, shown in Table 14-2, reflect broader trends in global nitrogen management and demonstrate that advanced economies are generally better able to achieve high crop yields while managing nitrogen fertilizer use efficiently (Zhang et al., 2015, p. 53). However, the fact that the global leader, Paraguay, has incomes roughly six times lower than that of the second-place United States, shows how factors separate from economic development matter substantially as well (World Bank, 2016). The presence of very wealthy countries, such as Singapore and the United Arab Emirates, among the laggards, shown in Table 14–3, reinforces this point further.

Three different explanations beyond economic development levels may help account for the position of Paraguay at the top and Singapore and the United Arab Emirates near the bottom, as well as broader trends observed in the tables above. The first, and most policy relevant explanation centers on direct regulations that limit nitrogen application to prevent pollution. The European Union implemented rules related to nitrogen fertilizer in 1991, which likely contributed to improvements in nitrogen use efficiency in Europe (The Council of the European Communities, 1991, p. 375/3; van Grinsven et al., 2012, pp. 5150–5151, 5158; Zhang et al., 2015, p. 53). These concerted policy efforts may help explain the presence of six EU countries among the top ten.

Large fertilizer subsidies may partially explain high levels of nitrogen pollution in China and India (Zhang et al., 2015, pp. 53–54). The cost of fertilizer relative to prices for agricultural products is important because it impacts the incentives of farmers to purchase and use fertilizer (Zhang et al., 2015, pp. 53–54). The ability to subsidize or tax agricultural products or fertilizer highlights the role policymakers play in setting these prices, and thus in encouraging both higher yields and sustainable application of nitrogen fertilizers. In particular, low fertilizer costs or high agricultural prices can incentivize farming practices that lower efficiency (Zhang et al., 2015, p. 54). Countries with high agricultural subsidies may benefit from the study of efforts to remove agricultural subsidies elsewhere. In the case of European nations, the removal of agricultural subsidies contributed to declines in nitrogen pollution (Zhang et al., 2015, pp. 53–54).

The types of crops grown in Argentina, Paraguay, Uruguay, and the United States help account for their high scores. Nitrogen use efficiency varies by crop type; therefore, differences in crops produced can have a major impact on the observed efficiency of a country (Zhang et al., 2015, pp. 51, 54, 55). Fruits and vegetables tend to have the lowest nitrogen efficiencies, while cereal crops tend to have higher efficiencies (Zhang et al., 2015, p. 55). Nitrogen-fixing crops, such as soybeans, tend to have the highest efficiencies of all crops (Zhang et al., 2015, p. 55). Soybeans account for a disproportionately large fraction of agricultural production Argentina, Paraguay, Uruguay and the United States, helping explain their success in managing nitrogen use (Central Intelligence Agency, 2017; Leff, Ramankutty, & Foley, 2004, p. 11; Zhang et al., 2015, p. 55). Similarly, the composition of the agricultural sector among the laggards further illustrates the role of crop type in determining nitrogen sustainability. Countries such as Singapore and the United Arab Emirates are known producers of nitrogen-inefficient crops (Central Intelligence Agency, 2017). The high proportion of fruit and vegetable production in these countries may help explain their poor performance.

In summary, the impacts of fertilizer or agricultural subsidies and regulations on fertilizer usage show the importance of government policy in encouraging the efficient use of nitrogen fertilizers. However, the differences in efficiency across crop types is important as well (Alexandratos & Bruinsma, 2012, pp. 124–125). The difference in crop mix also accounts for nearly half of the NUE difference between China and the USA (Zhang et al., 2015, p. 55). Thus,  technological efforts to increase yields without increasing fertilizer use for different types of crops – especially among the most nitrogen-inefficient crops – must become a key component of global strategies to improve agricultural sustainability (Zhang et al., 2015, p. 55).

Box 14-2. Feeding the world well: human nutrition indicators and their relevance to the Environmental Performance Index.

Stephen Wood
The Nature Conservancy
Yale School of Forestry & Environmental Studies

Global crop yields, and the ability to meet caloric needs, have risen dramatically since the mid-20th century. Yet crop yield – the most common metric of agricultural efficiency – is not necessarily a good proxy for the more than 50 nutrients needed in a balanced human diet. In fact, crop nutrient production was stagnant or declining while yields increased through the 20th century – see Figure 14–3 below. If the challenge of the 20th century was to feed the world, the challenge of the 21st century is to feed the world well, while minimizing impact on the environment.

In our team’s work, we have shown that nutrient diversity in national food supplies can be as important to nutrition-related health outcomes as total caloric availability (Remans, Wood, Saha, Anderman, & DeFries, 2014). There is growing consensus that optimizing food systems for micro- and macro-nutrients could more effectively address hunger and undernutrition than strictly increasing total food production (Remans et al., 2014)(Cassidy, West, Gerber, & Foley, 2013)(Negin, Remans, Karuti, & Fanzo, 2009)(R. DeFries et al., 2015)(Ruth DeFries et al., 2016). In recognition of this shift in attention, we have developed new diversity metrics to understand global and national patterns in diversity of food nutrients (Remans et al., 2014)(R. DeFries et al., 2015)(Ruth DeFries et al., 2016)(Wood, Smith, Fanzo, Remans, & DeFries, n.d.)(Wood, 2018). Understanding the nutritional deficiencies of food systems is essential to targeting the appropriate environmental footprint of agriculture so that both human and environmental needs are met.

What are the indicators?

Nutritional yield is the number of people whose nutrient needs could be met per hectare, for a specific crop and nutrient combination. It is calculated by multiplying the amount of a crop produced by the content of a particular nutrient for that crop and the dietary requirements for that nutrient. The advantage of this metric is its simple interpretation. A shortcoming is that it is not easily applied to systems with many food items and many nutrients, since it is calculated on a per nutrient-per food item basis. Potential nutrient adequacy is a single score that can be used to describe an entire food system, which is its advantage. To calculate potential nutrient adequacy, the nutrient content for all food items grown in a country are summed to get the total number of people whose nutritional needs could be met. Then, the average value across all nutrients is multiplied by the fraction of nutrients for which more than 100% of the country’s population can have their nutrient needs met. The score is therefore a combination of the magnitude of nutrient adequacy – average value across all nutrients, and the number of nutrients for which there is adequacy – fraction of nutrients potentially meeting > 100% needs. This reflects both that a population needs to meet multiple nutrients simultaneously, and that providing more nutrients can nourish more people. These metrics align with the goal of sustainable agriculture, which is to optimize potential nutrient adequacy rather than maximize total yield, while minimizing degradation of natural resources.


Figure 14-3
Figure 14-3. While global staple grain yields have increased (Panel a), nutritional production has stagnated or decreased (Panel b).
Note: Dietary Reference Intake (DRI).
Source: Alexandratos, N., & Bruinsma, J. (2012). World agriculture towards 2030/2050: the 2012 revision. (Working Paper No. 12-03). Rome: FAO.
Retrieved from http://www.fao.org/docrep/016/ap106e/ap106e.pdf

References

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Cassidy, E. S., West, P. C., Gerber, J. S., & Foley, J. A. (2013). Redefining agricultural yields: from tonnes to people nourished per hectare. Environmental Research Letters, 8(3), 034015. https://doi.org/10.1088/1748-9326/8/3/034015

Central Intelligence Agency. (2017). The World Factbook: Agriculture - Products. Washington, D.C. Retrieved from https://www.cia.gov/library/publications/the-world-factbook/fields/2052....

DeFries, R., Fanzo, J., Remans, R., Palm, C., Wood, S., & Anderman, T. L. (2015). Metrics for land-scarce agriculture. Science, 349(6245), 238–240. https://doi.org/10.1126/science.aaa5766

DeFries, R., Mondal, P., Singh, D., Agrawal, I., Fanzo, J., Remans, R., & Wood, S. (2016). Synergies and trade-offs for sustainable agriculture: Nutritional yields and climate-resilience for cereal crops in Central India. Global Food Security, 11, 44–53. https://doi.org/10.1016/j.gfs.2016.07.001

Eurostat, & Organisation for Economic Coöperation and Development. (2013). Nutrient Budgets - Methodology and Handbook. Retrieved from http://ec.europa.eu/eurostat/documents/2393397/2518760/Nutrient_Budgets_...(CPSA_AE_109)_corrected3.pdf/4a3647de-da73-4d23-b94b-e2b23844dc31

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Galloway, J. N., Aber, J. D., Erisman, J. W., Seitzinger, S. P., Howarth, R. W., Cowling, E. B., & Cosby, B. J. (2003). The Nitrogen Cascade (No. Vol. 53, No. 4). Bioscience. Retrieved from https://www.unc.edu/courses/2010spring/geog/595/001/www/Galloway2003.pdf

Hirel, B., Le Gouis, J., Ney, B., & Gallais, A. (2007). The challenge of improving nitrogen use efficiency in crop plants: towards a more central role for genetic variability and quantitative genetics within integrated approaches. Journal of Experimental Botany, 58(9), 2369–2387. https://doi.org/10.1093/jxb/erm097

Holtgrieve, G. W., Schindler, D. E., Hobbs, W. O., Leavitt, P. R., Ward, E. J., Bunting, L., … Wolfe, A. P. (2011). A Coherent Signature of Anthropogenic Nitrogen Deposition to Remote Watersheds of the Northern Hemisphere. Science, 334(6062), 1545–1548. https://doi.org/10.1126/science.1212267

Lassaletta, L., Billen, G., Garnier, J., Bouwman, L., Velazquez, E., Mueller, N. D., & Gerber, J. S. (2016). Nitrogen use in the global food system: past trends and future trajectories of agronomic performance, pollution, trade, and dietary demand. Environmental Research Letters, 11(9), 095007. https://doi.org/10.1088/1748-9326/11/9/095007

Leff, B., Ramankutty, N., & Foley, J. A. (2004). Geographic distribution of major crops across the world: GLOBAL CROP DISTRIBUTION. Global Biogeochemical Cycles, 18(1). https://doi.org/10.1029/2003GB002108

Milman, O. (2015, December 2). Earth has lost a third of arable land in past 40 years, scientists say. The Guardian. Retrieved from http://www.theguardian.com/environment/2015/dec/02/arable-land-soil-food...

Moll, R. H., Kamprath, E. J., & Jackson, W. A. (1982). Analysis and Interpretation of Factors Which Contribute to Efficiency of Nitrogen Utilization. Agronomy Journal, 74(3), 562–564. https://doi.org/10.2134/agronj1982.00021962007400030037x

Mueller, N. D., Lassaletta, L., Runck, B. C., Billen, G., Garnier, J., & Gerber, J. S. (2017). Declining spatial efficiency of global cropland nitrogen allocation: Cropland Nitrogen Allocation. Global Biogeochemical Cycles, 31, 245–257. https://doi.org/10.1002/2016GB005515

National Public Radio. (2017, August 3). The Gulf Of Mexico’s Dead Zone Is The Biggest Ever Seen. Retrieved January 17, 2018, from https://www.npr.org/sections/thesalt/2017/08/03/541222717/the-gulf-of-me...

Negin, J., Remans, R., Karuti, S., & Fanzo, J. C. (2009). Integrating a broader notion of food security and gender empowerment into the African Green Revolution. Food Security, 1(3), 351–360. https://doi.org/10.1007/s12571-009-0025-z

Oita, A., Malik, A., Kanemoto, K., Geschke, A., Nishijima, S., & Lenzen, M. (2016). Substantial nitrogen pollution embedded in international trade. Nature Geoscience, 9(2), 111–115. https://doi.org/10.1038/ngeo2635

Remans, R., Wood, S. A., Saha, N., Anderman, T. L., & DeFries, R. S. (2014). Measuring nutritional diversity of national food supplies. Global Food Security, 3(3–4), 174–182. https://doi.org/10.1016/j.gfs.2014.07.001

Reytar, K., Hanson, C., & Henninger, N. (2014). Indicators of sustainable agriculture: a scoping analysis. In Working Paper, Installment 6 of Creating a Sustainable Food Future. World Resources Institute Washington, DC. Retrieved from https://www.wri.org/sites/default/files/wrr_installment_6_sustainable_ag...

Rockström, J., Steffen, W., Noone, K., Persson, Å., Chapin, F. S. I., Lambin, E., … Foley, J. (2009a). Planetary Boundaries: Exploring the Safe Operating Space for Humanity. Ecology and Society, 14(2). https://doi.org/10.5751/ES-03180-140232

Rockström, J., Steffen, W., Noone, K., Persson, Å., Chapin, F. S., Lambin, E. F., … Foley, J. A. (2009b). A safe operating space for humanity. Nature, 461(7263), 472–475. https://doi.org/10.1038/461472a

Royal Society (Great Britain), & Fowler, D. (2008). Ground-level ozone in the 21st century: future trends, impacts and policy implications. London: The Royal Society. Retrieved from http://royalsociety.org/policy/publications/2008/ground-level-ozone/

Sachs, J., Schmidt-Traub, G., Kroll, C., Durand-Delacre, D., & Teksoz, K. (2017). SDG Index and Dashboards Report 2017 (p. 479). New York: Bertelsmann Stiftung and Sustainable Development Solutions Network (SDSN). Retrieved from http://www.sdgindex.org/assets/files/2017/2017-SDG-Index-and-Dashboards-...

Sutton, M. A., Bleeker, A., Howard, C.M., Bekunda, M., Grizzetti, B., de Vries, W., … Davidson, E.A. (Eds.). (2013). Our nutrient world: the challenge to produce more food and energy with less pollution; [global overview on nutrient management]. Edinburgh: Centre for Ecology & Hydrology.

Sutton, M. A., Oenema, O., Erisman, J. W., Leip, A., van Grinsven, H., & Winiwarter, W. (2011). Too much of a good thing. Nature, 472(7342), 159–161. https://doi.org/10.1038/472159a

The Council of the European Communities. Council Directive of 12 December 1991 concerning the protection of waters against pollution caused by nitrogen from agricultural sources, 91/676/EEC § (1991). Retrieved from http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:31991L0676&...

United Nations. (n.d.). Goal 2: End hunger, achieve food security and improved nutrition and promote sustainable agriculture. Retrieved December 3, 2017, from http://www.un.org/sustainabledevelopment/hunger/

United Nations News Centre. (2016, April 4). New UN Decade aims to eradicate hunger, prevent malnutrition. Retrieved from http://www.un.org/apps/news/story.asp?NewsID=53605

van Grinsven, H. J. M., ten Berge, H. F. M., Dalgaard, T., Fraters, B., Durand, P., Hart, A., … Willems, W. J. (2012). Management, regulation and environmental impacts of nitrogen fertilization in northwestern Europe under the Nitrates Directive; a benchmark study. Biogeosciences, 9(12), 5143–5160. https://doi.org/10.5194/bg-9-5143-2012

Wood, S. (2018). Nutritional functional trait diversity of crops in south-eastern Senegal. Journal of Applied Ecology.

Wood, S., Smith, M., Fanzo, J., Remans, R., & DeFries, R. (n.d.). Trade increases equitability of food nutrients in the global food system. Nature Sustainability.

World Bank. (2016). GDP per capita, PPP (current international $). Retrieved February 1, 2018, from https://data.worldbank.org/indicator/NY.GDP.PCAP.PP.CD?view=chart

World Bank. (2017a). Data: Agriculture, value added (current US$). Retrieved from http://data.worldbank.org/indicator/NV.AGR.TOTL.CD?end=2016&start=1960&v...

World Bank. (2017b). Enabling the Business of Agriculture 2017. The World Bank. https://doi.org/10.1596/978-1-4648-1021-3

Zhang, X. (2017). A plan for efficient use of nitrogen fertilizers. Nature, 543, 322–323. https://doi.org/10.1038/543322a

Zhang, X., & Davidson, E. (2016). Sustainable Nitrogen Management Index (SNMI): methodology. University of Maryland Center for Environmental Science.

Zhang, X., Davidson, E. A., Mauzerall, D. L., Searchinger, T. D., Dumas, P., & Shen, Y. (2015). Managing nitrogen for sustainable development. Nature. https://doi.org/10.1038/nature15743

Alexandratos, N., & Bruinsma, J. (2012). World agriculture towards 2030/2050: the 2012 revision. (Working Paper No. 12-03). Rome: FAO. Retrieved from http://www.fao.org/docrep/016/ap106e/ap106e.pdf

Bodirsky, B. L., Popp, A., Lotze-Campen, H., Dietrich, J. P., Rolinski, S., Weindl, I., … Stevanovic, M. (2014). Reactive nitrogen requirements to feed the world in 2050 and potential to mitigate nitrogen pollution. Nature Communications, 5. https://doi.org/10.1038/ncomms4858

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DeFries, R., Mondal, P., Singh, D., Agrawal, I., Fanzo, J., Remans, R., & Wood, S. (2016). Synergies and trade-offs for sustainable agriculture: Nutritional yields and climate-resilience for cereal crops in Central India. Global Food Security, 11, 44–53. https://doi.org/10.1016/j.gfs.2016.07.001

Eurostat, & Organisation for Economic Coöperation and Development. (2013). Nutrient Budgets - Methodology and Handbook. Retrieved from http://ec.europa.eu/eurostat/documents/2393397/2518760/Nutrient_Budgets_...(CPSA_AE_109)_corrected3.pdf/4a3647de-da73-4d23-b94b-e2b23844dc31

Food and Agriculture Organization. (2016). Submission by the Food and Agriculture Organization of the United Nations (FAO) to The United Nations Framework Convention on Climate Change (UNFCCC) on Issues relating to agriculture: agricultural practices and technologies (No. FCCC/SBSTA/2014/L.14). Rome: United Nations Framework Convention on Climate Change. Retrieved from https://unfccc.int/files/documentation/submissions_from_non-party_stakeh...

Food and Agriculture Organization of the United Nations. (2011). The state of the world’s land and water resources for food and agriculture - managing systems at risk (1st ed). Rome and Earthscan, London.

Galloway, J. N., Aber, J. D., Erisman, J. W., Seitzinger, S. P., Howarth, R. W., Cowling, E. B., & Cosby, B. J. (2003). The Nitrogen Cascade (No. Vol. 53, No. 4). Bioscience. Retrieved from https://www.unc.edu/courses/2010spring/geog/595/001/www/Galloway2003.pdf

Hirel, B., Le Gouis, J., Ney, B., & Gallais, A. (2007). The challenge of improving nitrogen use efficiency in crop plants: towards a more central role for genetic variability and quantitative genetics within integrated approaches. Journal of Experimental Botany, 58(9), 2369–2387. https://doi.org/10.1093/jxb/erm097

Holtgrieve, G. W., Schindler, D. E., Hobbs, W. O., Leavitt, P. R., Ward, E. J., Bunting, L., … Wolfe, A. P. (2011). A Coherent Signature of Anthropogenic Nitrogen Deposition to Remote Watersheds of the Northern Hemisphere. Science, 334(6062), 1545–1548. https://doi.org/10.1126/science.1212267

Lassaletta, L., Billen, G., Garnier, J., Bouwman, L., Velazquez, E., Mueller, N. D., & Gerber, J. S. (2016). Nitrogen use in the global food system: past trends and future trajectories of agronomic performance, pollution, trade, and dietary demand. Environmental Research Letters, 11(9), 095007. https://doi.org/10.1088/1748-9326/11/9/095007

Leff, B., Ramankutty, N., & Foley, J. A. (2004). Geographic distribution of major crops across the world: GLOBAL CROP DISTRIBUTION. Global Biogeochemical Cycles, 18(1). https://doi.org/10.1029/2003GB002108

Milman, O. (2015, December 2). Earth has lost a third of arable land in past 40 years, scientists say. The Guardian. Retrieved from http://www.theguardian.com/environment/2015/dec/02/arable-land-soil-food...

Moll, R. H., Kamprath, E. J., & Jackson, W. A. (1982). Analysis and Interpretation of Factors Which Contribute to Efficiency of Nitrogen Utilization. Agronomy Journal, 74(3), 562–564. https://doi.org/10.2134/agronj1982.00021962007400030037x

Mueller, N. D., Lassaletta, L., Runck, B. C., Billen, G., Garnier, J., & Gerber, J. S. (2017). Declining spatial efficiency of global cropland nitrogen allocation: Cropland Nitrogen Allocation. Global Biogeochemical Cycles, 31, 245–257. https://doi.org/10.1002/2016GB005515

National Public Radio. (2017, August 3). The Gulf Of Mexico’s Dead Zone Is The Biggest Ever Seen. Retrieved January 17, 2018, from https://www.npr.org/sections/thesalt/2017/08/03/541222717/the-gulf-of-me...

Negin, J., Remans, R., Karuti, S., & Fanzo, J. C. (2009). Integrating a broader notion of food security and gender empowerment into the African Green Revolution. Food Security, 1(3), 351–360. https://doi.org/10.1007/s12571-009-0025-z

Oita, A., Malik, A., Kanemoto, K., Geschke, A., Nishijima, S., & Lenzen, M. (2016). Substantial nitrogen pollution embedded in international trade. Nature Geoscience, 9(2), 111–115. https://doi.org/10.1038/ngeo2635

Remans, R., Wood, S. A., Saha, N., Anderman, T. L., & DeFries, R. S. (2014). Measuring nutritional diversity of national food supplies. Global Food Security, 3(3–4), 174–182. https://doi.org/10.1016/j.gfs.2014.07.001

Reytar, K., Hanson, C., & Henninger, N. (2014). Indicators of sustainable agriculture: a scoping analysis. In Working Paper, Installment 6 of Creating a Sustainable Food Future. World Resources Institute Washington, DC. Retrieved from https://www.wri.org/sites/default/files/wrr_installment_6_sustainable_ag...

Rockström, J., Steffen, W., Noone, K., Persson, Å., Chapin, F. S. I., Lambin, E., … Foley, J. (2009a). Planetary Boundaries: Exploring the Safe Operating Space for Humanity. Ecology and Society, 14(2). https://doi.org/10.5751/ES-03180-140232

Rockström, J., Steffen, W., Noone, K., Persson, Å., Chapin, F. S., Lambin, E. F., … Foley, J. A. (2009b). A safe operating space for humanity. Nature, 461(7263), 472–475. https://doi.org/10.1038/461472a

Royal Society (Great Britain), & Fowler, D. (2008). Ground-level ozone in the 21st century: future trends, impacts and policy implications. London: The Royal Society. Retrieved from http://royalsociety.org/policy/publications/2008/ground-level-ozone/

Sachs, J., Schmidt-Traub, G., Kroll, C., Durand-Delacre, D., & Teksoz, K. (2017). SDG Index and Dashboards Report 2017 (p. 479). New York: Bertelsmann Stiftung and Sustainable Development Solutions Network (SDSN). Retrieved from http://www.sdgindex.org/assets/files/2017/2017-SDG-Index-and-Dashboards-...

Sutton, M. A., Bleeker, A., Howard, C.M., Bekunda, M., Grizzetti, B., de Vries, W., … Davidson, E.A. (Eds.). (2013). Our nutrient world: the challenge to produce more food and energy with less pollution ; [global overview on nutrient management]. Edinburgh: Centre for Ecology & Hydrology.

Sutton, M. A., Oenema, O., Erisman, J. W., Leip, A., van Grinsven, H., & Winiwarter, W. (2011). Too much of a good thing. Nature, 472(7342), 159–161. https://doi.org/10.1038/472159a

The Council of the European Communities. Council Directive of 12 December 1991 concerning the protection of waters against pollution caused by nitrogen from agricultural sources, 91/676/EEC § (1991). Retrieved from http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:31991L0676&...

United Nations. (n.d.). Goal 2: End hunger, achieve food security and improved nutrition and promote sustainable agriculture. Retrieved December 3, 2017, from http://www.un.org/sustainabledevelopment/hunger/

United Nations News Centre. (2016, April 4). New UN Decade aims to eradicate hunger, prevent malnutrition. Retrieved from http://www.un.org/apps/news/story.asp?NewsID=53605

van Grinsven, H. J. M., ten Berge, H. F. M., Dalgaard, T., Fraters, B., Durand, P., Hart, A., … Willems, W. J. (2012). Management, regulation and environmental impacts of nitrogen fertilization in northwestern Europe under the Nitrates Directive; a benchmark study. Biogeosciences, 9(12), 5143–5160. https://doi.org/10.5194/bg-9-5143-2012

Wood, S. (2018). Nutritional functional trait diversity of crops in south-eastern Senegal. Journal of Applied Ecology.

Wood, S., Smith, M., Fanzo, J., Remans, R., & DeFries, R. (n.d.). Trade increases equitability of food nutrients in the global food system. Nature Sustainability.

World Bank. (2016). GDP per capita, PPP (current international $). Retrieved February 1, 2018, from https://data.worldbank.org/indicator/NY.GDP.PCAP.PP.CD?view=chart

World Bank. (2017a). Data: Agriculture, value added (current US$). Retrieved from http://data.worldbank.org/indicator/NV.AGR.TOTL.CD?end=2016&start=1960&v...

World Bank. (2017b). Enabling the Business of Agriculture 2017. The World Bank. https://doi.org/10.1596/978-1-4648-1021-3

Zhang, X. (2017). A plan for efficient use of nitrogen fertilizers. Nature, 543, 322–323. https://doi.org/10.1038/543322a

Zhang, X., & Davidson, E. (2016). Sustainable Nitrogen Management Index (SNMI): methodology. University of Maryland Center for Environmental Science.

Zhang, X., Davidson, E. A., Mauzerall, D. L., Searchinger, T. D., Dumas, P., & Shen, Y. (2015). Managing nitrogen for sustainable development. Nature. https://doi.org/10.1038/nature15743