Sustainability Challenges in the Phosphorus System

Abstract

The global food system relies upon a constant flow of phosphors fertiliser, a great part of which causes extensive environmental damage through inefficient application. This puts phosphorus at the centre of two crucial challenges humanity faces over the next century: feeding a growing population on a finite resource, and limiting the release of pollutants, thereby maintaining a safe global ecosystem. Based on an in-depth review of the literature, this study provides a broad background of the various aspects of the phosphorus system, though examining the physical, geopolitical, economic and technological restraints on supply, alongside the drivers of demand. From this, possible interventions in the system that could direct the world towards phosphorus sustainability are explored, and set within four scenarios as a means to inform debate about policy options.

Table of Contents

1. Introduction 2 ..............................................................................................................................................2. The Phosphorus System 2 ...........................................................................................................................

2.1. The History of Phosphorus 2 2.2. Reserves and Resources 3 2.3. Modern Phosphate Output 4 2.4. The Environmental Impact 4

2.4.1.Application of fertiliser 4 2.4.2.Mining 5

3. Constraints on Supply 5 ..............................................................................................................................3.1. Physical Scarcity 6 3.2. Geopolitical Considerations 7

3.2.1.National Outputs 7 3.2.2.China 8 3.2.3.European Union 8 3.2.4.Morocco 9

3.2.4.1.International Relations 9 3.2.4.2.Internal Vulnerability 9 3.2.4.3.Western Sahara 10

3.3. Further Supply Questions 11 4. Drivers of Demand 11 .................................................................................................................................

4.1. Population and Diets 12 4.2. Further Demand Questions 12

4.2.1.Non-food Uses 12 4.2.2.Waste and Distribution 13

5. Points of Intervention 14 ............................................................................................................................5.1. Demand 14

5.1.1.Food 14 5.1.2.Agricultural and Food Chain Efficiency 14

5.2. Supply 15 5.3. Global Governance 16

6. Scenarios 16 .................................................................................................................................................6.1. Baseline 17 6.2. Ambitious Climate Policy 18 6.3. Geopolitical Disruption 19 6.4. Phosphorus Sustainability 20

7. Conclusions 22 .............................................................................................................................................8. References 22...............................................................................................................................................

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1. Introduction

Application of phosphorus fertiliser has dramatically increased capacity for food production, and with this has come staggering growth in populations, which are reliant on this fundamental nutrient. The dependance upon a non-renewable resource, combined with highly concentrated reserves, has significant implications for world food security, and has been described as “the most important quasi-monopoly in economic history” (Grantham, 2012). Simultaneously, the widespread use of fertiliser containing phosphate rock has severely disrupted the natural phosphorus cycle, and humans have far exceeded the planetary boundaries for phosphorus flux (Carpenter and Bennett, 2011), with the anthropogenic flow eight times greater than the natural (Rockström et al., 2009). The importance of phosphorus in the global food system, combined with the environmental impacts of its use, should place this resource at the heart of discussions about sustainable development. Yet, it has received relatively little attention from those in a position to influence policy. In the UK, for example, there is rarely press on the subject of phosphorus security, matched by limited academic analysis of future scenarios (Cooper and Carliell-Marquet, 2013; Neset et al., 2016; Lyon, 2018).

Phosphorus is an essential and irreplaceable element in the cellular processes of all plants, and as such current food production cannot be sustained without phosphorus fertiliser (Edixhoven et al., 2014; Chowdhury et al., 2017). As a finite fossil resource, establishing phosphorus sustainability is thus essential for global food security, defined by the FAO (1996) as when “all people, at all times, have physical and economic access to sufficient, safe and nutritious food that meets dietary needs and food preferences for an active and healthy life”. Although food security has been included in the Millennium Development Goals, and more recently as part of the Sustainable Development Goals (UNDP, 2016), the eradication of food poverty is far from achieved, and hunger persists throughout the world with 821 million people considered undernourished today (Mbow et al., 2019).

To feed a growing population and preserve global ecosystems the world has to move towards a sustainable phosphorus system. This would be resilient to supply shocks, ethical, monitored and transparent. Importantly, it would mean phosphorus is accessible and affordable to all farmers now and in the future, and the environmental impacts of its use would be limited (Cordell et al., 2009a). This is expanded by Childers et al., (2013) to include the globalisation of knowledge and technology, but with a global economy shifting away from market forces and towards regional innovation. This study will highlight how sustainable phosphorus management plays a vital role in future of both food security and environmental protection. To do so, an extensive background on the phosphorus system is provided. This is followed by an exploration of possible future supply and demand challenges, and a discussion of how these can be mitigated by interventions in the system. Lastly, these factors are taken in the context of four exploratory scenarios, that compare how different global developments could play out with regard to phosphorus sustainability.

2. The Phosphorus System

2.1. The History of Phosphorus

The use of phosphorus to enhance plant growth began long before the emergence of modern chemical fertiliser, with phosphorus added to soils in the form of manure since the dawn of agriculture. Yet it wasn’t until the discovery of the element phosphorus (P), 350 years ago, that we began to understand the role of the nutrient as a component of plant development (Peterson, 2019). Alongside manure, ash has also been used as a source of phosphorus to increase soil productive capacity, but as demand for food grew in line with growing populations, other sources had to be explored. During the 19th century, waves of phosphorus supply came in the form of bone, followed by accumulated bird manure (guano). Both of these, however, where rapidly depleted (Mikkelsen, 2019), and so attention was turned to phosphate rock, and the modern phosphorus industry began.

Mineral phosphate rock deposits were first found in England in 1847, and later around the world. Relatively cheap and easy to mine, this soon became the predominant source of phosphorus, although widespread use only began to grow exponentially after the Second World War. The green revolution that introduced high-yielding crop varieties and sustained an exploding global population was fuelled by nitrogen and phosphorus fertiliser, the use of which rose six-fold between 1950 to 2000 (Ashley et al., 2011). In the 1970s, phosphoric acid was used to produce triple superphosphate, and in doing so greatly concentrated phosphorus, reducing transport and labour costs. This has gradually been replaced with ammonium phosphates (Mikkelsen, 2019), with the most prominent diammonium phosphate (DAP).

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2.2. Reserves and Resources The United States Geological Survey (USGS) provides annual statistics of global phosphate reserves, which is the most commonly used dataset both in industry and academia, and is used in this study. However, it should be noted that the actual quantities are often uncertain. Partly as it is not always in the interest of countries or companies to make data publicly available (Walan et al., 2014), and furthermore because of the confusion in defining how much of a resource exists, and how much can be extracted.

A distinction between reserves and resources is fundamental to any discussion about the longevity of a material, yet within the phosphate industry it is sometimes unclear. Reserves are defined as phosphate rock that can be extracted economically using existing technology, while resources are the total amount of phosphate that may be extractable at some point in the future, with price increases enabling technological developments. Although this difference is universally understood, not all datasets use the same categorisations, with major implications for estimating longevity.

Confusion in the literature is exemplified by the different classifications used by two of the most prominent authorities on phosphorus statistics. The USGS classes reserves, reserve base and resources, while the International Fertilizer Development Center (IFDC) uses just reserves and resources (Van Kauwenbergh, 2010), making it difficult to categorise future avalibility of the rock. Just as important is the difference between phosphate rock ore and concentrate, which is scarcely noted in the majority of recently published articles on the subject, and causes considerable misunderstanding. Concentrate is ore that has been upgraded to a marketable product, usually requiring 30 % P2O5 (Edixhoven et al., 2014). The distinction between reserves, resources, ore and concentrate is vitally important for any estimates of the longevity of supply. However, individual countries still report their deposits using different terminology, which is supposedly normalised by the USGS, although the preciseness of this validation has been questioned repeatedly (Van Vuuren et al., 2010; Edixhoven et al., 2014). This ambiguity needs to be considered in any future scenarios as not everyone will be aware of the uncertainty on either side of reserve estimates that are used to formulate policy.

The global share of phosphate rock reserves is shown in Figure 1. Until 2007, China had the largest share of reserves (Chowdhury et al., 2016). But, in a development that drastically changed the outlook on phosphorus availability, Morocco’s reserve figures were increased from 5,600 to 51,000 million metric tonnes (Mt) between 2009 and 2010 after a reassessment of mining data, dwarfing all other countries (USGS, 2013). These figures were adopted by the IFDC and used by authors in later years to estimate peak scenarios. However, the estimates are disputed (see Global Phosphorus Research Initiative, 2010), and there are questions over the labelling of phosphate rock as concentrate, potentially making Moroccos figures incomparable with USGS reports for other countries. Edixhoven et al. (2013) note that after USGS adopted these estimates, Algeria, Iraq and Syria immediately updated their reserves to include a higher figure, which were labeled as ‘discoveries’. These were likely to be reconsiderations of ore resources to ore reserves (simply relabelled as concentrate), evidently a political move rather than a geological finding, yet Scholz and Wellmer (2015) argue that the IFDC and USGS figures were valid, and the upgrade in Moroccan estimates can be accepted. Nevertheless, it can be seen how easily data can be manipulated through the example of how Iraqi phosphate figures have changed over time. In 2011 reserves were submitted as 5800Mt phosphate rock, raising huge excitement to the mining community (Blair, 2011), but were quietly downgraded to 430Mt

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Figure 1. Global phosphate reserves in Mt (million metric tons). Data from USGS (2019).

in 2013 because the incorrect classification system had been used (Scholz et al., 2014). This highlights how figures are vulnerable to artificial adjustment for political and economic advantage, and brings to attention the drawback of limited disclosure that mining companies claim through commercial confidence.

2.3. Modern Phosphate Output

The top 20 global producers of phosphate rock in 2016 are shown in Figure 2. Since 2005, when China overtook the US as the lead producer of phosphate (USGS, 2006), the country has been the predominant driver of growth in phosphate production around the world. Morocco meanwhile is the largest exporter, with 36.7% of the export market (OCP, 2011). Globally in 2016, 255Mt phosphate rock was produced. which translates to 77.2Mt P2O5 (the common denominator usually used in the agricultural industry) or 33.7Mt phosphorus. Most recently, the Mosaic company finds leading phosphate product shipments to have risen at 1.5% from 2010 to 2015, and 2% up to 2018 (Rham, 2018).

It is important to note that there is an essential difficulty in quantifying the global trade in phosphorus, as the route, both physical and through international ownership, from mine to fork is rarely direct. Phosphorus deposited in rock mined from one country can pass through several others as it is processed into fertiliser, applied to fields, and eventually consumed in agricultural products, sometime via animal feed, adding yet another step (Cordell and White, 2011). This often makes statistics regarding

imports and exports misleading, as consumption can be raised by increasing imports or deceasing exports (Geissler et al., 2019). The US, for example, is the leading importer of phosphate rock, but a significant amount of that is eventually exported as DAP and phosphoric acid (Jasinski, 2016). As the US Mosaic Company recently decided to invest in a Saudi Arabian deposit (Mosaic Co., 2013), US ‘consumption’ of phosphate rock will be less than it would have been had processing continued at an existing Florida plant, despite fertiliser use in the US continuing at a steady pace (Jarvie et al., 2015).

2.4. The Environmental Impact

2.4.1. Application of fertiliser

The detrimental impact of nitrogen fertiliser runoff into freshwater and marine ecosystems is well known to the public, but phosphorus fertiliser can have equally grave, and in some cases greater consequences (Chowdhury and Chakraborty, 2016). Not all fertiliser applied to a field is taken up by plants, and while some is stored in the soil, a considerable amount leaches into waterways, that feed into rivers, lakes, aquifers, and ultimately the ocean. These excess nutrients accelerate aquatic plant growth, which is known as eutrophication. In itself, this algae can be toxic for aquatic life as well as humans (James at al., 2010), but further to this, water is starved of oxygen due to the increased demand (hypoxia), and sometimes completely deprived of it (anoxia). This process has spread devastatingly around the world in recent decades (Elser et al., 2007), and can lead to a change in the make-up of aquatic vegetation, mass fish death, and an overall loss of biodiversity (Smith and Schindler, 2009). Costal hypoxia contributes to ocean acidification, with major

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Figure 2. Global Phosphate mine production1998-2018. Data from USGS (2002-2019). 1. Moroccan production data includes phosphate originating from Western Sahara. e. Estimated figures

detrimental impacts on corals, mollusks and crustaceans, and elevated CO2 in ocean waters (Howarth et al., 2011). Meanwhile in the extreme case of anoxia no fish can survive, and the whole ecosystem collapses, forming dead zones (Carpenter, 2008). Ultimately, this application of fertiliser to increase crop yields has the sardonic effect of reducing the number fish available to harvest, and severely impacting food security.

Past increases in ocean phosphate levels of only 20 per cent compared to the natural flow has been identified as one of the drivers of total collapse in ocean oxygen levels, known as Ocean Anoxic Events (OAEs) (Bonneuil and Fressoz, 2016). These OAEs are caused by increased phosphorus availability driving increased ocean productivity, that leads to higher oxygen demand. Once this begins at scale, feedbacks in the ocean system can amplify the effects, with low oxygen levels inducing increased phosphorus release from ocean sediments, this can ultimately lead to OEAs lasting hundreds of thousands of years (Watson et al., 2017). The result is massive extinction of aquatic life, seen during global environmental crisis points, notably the End-Permian Extinction (Wignall and Twitchett, 1996), widely regarded as the most significant of the great mass-extinctions (Benton, 2005). These past events have been associated with increased weathering of continental rocks during warmer eras, sending more nutrients into the ocean. However, there is concern that humans are artificially promoting these conditions, and in the future, oxygen levels could fall to critical levels with massive impacts on the global ecosystem (Watson et al., 2017).

The fertiliser that remains in the soil can contain a high proportion of impurities, including heavy metals like cadmium. Research is clear that there is a direct link between fertiliser application and increasing cadmium levels in soils (Pan et al., 2010), and there is an ongoing debate over impacts on human health (see 3.2.3). There are also concerns over the radioactive contents of some mined rock, to such an extent that the byproduct of phosphate mining has been considered as a source for nuclear energy (Gabriel et al., 2013). The presence of uranium and thorium, which are linked to cancer and kidney failure, poses a particular risk to miners, but also to the end users, farmers, and even those consuming food grown using a significant amount phosphate fertiliser may be at risk. The link between fertiliser use and such disease has been difficult establish, and current research is still divided (see Tirado and Allsopp, 2012).

Overall, anthropogenic phosphorus input to freshwater estimates vary from 2 to 20Mt phosphorus/year. (Scholz and Wellmer, 2019). With increased phosphorus use, this leaching into waterways will also rise. Some expect up to a 3 fold increase in phosphorus-driven eutrophication in freshwater and costal ecosystems by 2050 from 2000 levels, if agricultural production continues to expand (Tilman et al., 2001).

2.4.2. Mining

Before fertiliser is applied to fields, a considerable amount of waste is produced, which is often left in slag piles that can leach heavy metals and other contaminants (notably arsenic and lead) into waterways, or blow them into nearby towns (Yang et al., 2015). During processing, each tonne of phosphorus generates five tonnes of phosphogypsum waste (Cordell and White, 2011). In the US this is deposited in slurry piles far from population centres, but in Morocco it is routinely dumped into the ocean (White, 2015), with unknown impacts on marine ecosystems. The risk posed to those working on, and living in proximity to phosphate mines has been known for some time (Fleischer, 1981; Bigu et al., 2000). However, there is limited recent research on the direct health impacts on workers, despite several studies noting increased toxicity around phosphate mines due to radioactive elements and heavy metals present in the rock, with children particularly vulnerable (Al-Hwaiti et al., 2014; Idardare et al., 2013).

Along with the direct impact of phosphate mining and the application of fertiliser, the indirect impact on the planet is also considerable. Most notably the immense energy requirements for the mining and transportation of phosphate rock around the world, and the carbon emissions that come with processing rock into fertiliser. As those reserves easiest to access and purest are exhausted first, impurities will increase in the future (Cordell and White 2014), meaning there will be more waste to dispose of, further energy costs, and elevated greenhouse gas emissions. The enduring result of these various forms of environmental degradation has to be considered when examining future farming scenarios that may be based on high fertiliser use. There is a question as to whether the ecological costs of producing more food will lead to more suffering in the long term, as habitats are destroyed and the ability of the planet to sustain life is gradually eroded.

3. Constraints on Supply

The trajectory of future phosphorus supply depends primarily on the longevity of phosphate rock resources and the ability to access them, so actual reserve figures are explored here first. However, resource scarcity

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involves questions of management, geopolitics, economics and institutions as much as the physical reserves. Therefore, while it is important to understand how much there is left in the ground, the focus has to extend far beyond physical scarcity for any predictions to be made regarding the future availability of phosphate. One possible interruption to supply could be a shift in local and international politics, and hence for a geopolitical perspective, recent small scale supply shifts are analysed to understand what might cause shocks in the short term. This is followed by two case studies of supply disruptions, one of a major producer, China, and another of a major importer, the European Union (EU). Ultimately, however, in the longer term, the focus must be turned to Morocco, where production will be increasingly heavily concentrated. This is followed by a discussion of other external threats to supply.

3.1. Physical Scarcity

One of the driving forces behind the global food price shock of 2006-2008 was the cost of mineral fertilisers (FAO, 2011). Around the same time in 2008, there was a massive rise in the prise of phosphate, which spurred recent interest in the long-term sustainability of the resource. The price of phosphate rock rose 8,000% (Phosphorus Futures, 2019) after a combination of factors coincided, including lowered production in the US, increased biofuel demand, stock market speculation, and a lack of investment (Cordell et al., 2009a). This directly raised the price of DAP four fold (Chowdhury et al., 2017) and gave rise to so-called ‘fertiliser riots’ (Vidal, 2008). The price spike also drove countries to reduce exports in order to protect domestic supplies, most notably in China (see 3.2.2) but also in other exporting countries (Khabarov and Obersteiner, 2017). Since then, however, quantities of mined phosphate have increased exponentially over the last decade, with 160Mt mined in 2009, and 270Mt mined in 2018 (USGS 2019).

This price shock, along with the reclassification of Moroccan reservers, threw into disarray many estimates of how long we will be able to extract phosphate. Estimating the lifetime of a non-renewable material comes with certain difficulties that have prompted considerable debate over how we calculate longevity. The key question is whether to give the lifetime as that of current reserves, which could put depletion within decades (Walan et al., 2014). Or, because as the rock reserves are depleted, resources become economically feasible, the total ultimately recoverable resources (URR), as argued by Scholz and Wellmer, 2015. This however obscures the fundamental question, as URR data is much harder to acquire, and estimates of a depletion year range from between 70 to 400 years away (Sverdrup et al., 2011; Cooper et al., 2011; Li et al., 2018).

Some authors take this timescale to argue that concerns over phosphate depletion in the near future are unwarranted (e.g. Van Kauwenbergh, 2010; Chowdhury et al., 2017). However others point out that as higher-quality and easier to access resources are mined first, the quality (phosphorus content) is gradually falling, from 15% in 1970 to 13% by 1996 (Smil, 2000). Although this is generally acknowledged in future scenarios (e.g. Van Vuuren et al., 2010; Neset et al., 2016), it is rarely included in the calculations that follow, with most using a constant figure of 30% P2O5 (i.e. 13% phosphorus). This means that estimates of longevity and price may be misguided, and as quality continues to fall, in the long term energy inputs and so costs will have to rise, especially as the increase is exponential: As ore quality falls, more rock needs to be mined to obtain the same nutrient content. This is an important part of Cordell and White’s (2011) argument that the critical point guiding policy decisions, when annual production can no longer keep up with rising demand, will be reached much sooner than when 100% of reserves are depleted.

This peak in phosphate production has been predicted to occur within this century (Mohr and Evans, 2013; Walan, 2013), and even as soon as 2035 (Cordell and White, 2014). Yet the the estimating of peak production has been heavily criticised for lack of consideration of technological developments, market dynamics, and limited knowledge of URR (De Ridder et al., 2012; Vaccari et al., 2014). The impact of technology has been especially debated, with Scholz and Wellmer (2019) arguing an increase in phosphorus price would not endanger the global food supply. On the other hand, Sverdrup et al. (2011) find that price increases will only come after the resource has become too scarce, and too wasted, for more efficient practices to have an impact, and expects scarcity to begin to appear within the next 100 years, with associated increases in food prices and social challenges. This is why Cordell and White (2014) argue that market mechanisms cannot be relied upon to improve extractive technology and force consumption limits, especially given the unique position of phosphorus in feeding the planet.

Globally in 2011, 63% of phosphorus was consumed in the producing countries, with the biggest producers, the US and China, consuming most of their product (USGS, 2019). At current projections, studies have estimated these two countries have between 30 and 60 years left of phosphate supply (Powers et al., 2019; Chowdhury et al., 2017). Thus, the main question of supply in the medium term is not when we will run out,

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but what will happen once reserves are depleted in countries where production and demand are both high, such as the US and China. As these become too expensive, protected, and eventually exhausted, Moroccan output will develop into a near-monopoly position, with the Kingdom’s share of global production expected to rise to 80% by 2100 (Cooper et al., 2011). With world fertiliser supply, and thus food security, reliant on one country, there are serious questions to be raised about supply shocks and the vulnerability of prices. Van Vuuren et al. (2010) argue that a short term disruption would not lead to a food crisis, but in regions where limited soil phosphorus availability cannot buffer a disruption to fertiliser supply, there would likely be implications for crop productivity. Particularly so in Sub-Saharan Africa, where the highest rate of growth in fertiliser demand will come from (Van den Berg et al., 2016; IFA, 2018), and where Cordell at al. (2009) argue it will be decades before agricultural soils there reach a point of phosphorus sustainability.

3.2. Geopolitical Considerations

For some time phosphorus reserves have played an important but rarely reported role in global politics. Nauru, for example, once had extensive high-quality phosphate deposits, and in the early 20th century, as Australia increased agricultural output, the state was relied upon for essential fertilisers. Australia took control of the island at the onset the First World War, and threatened to refuse to sign the treaty of Versailles if the United States didn’t allow access to the island to mine phosphate (Gale, 2019). Control over the supply of phosphate is now attracting more attention, as exemplified in the investment major economies like China and the US are putting into expanding phosphate capabilities globally. In 2018, for example, the leading fertiliser company based in the US purchased five phosphate rock mines and four phosphate fertiliser plants in Brazil alone (USGS, 2019).

3.2.1. National Outputs

Local and national conflict can have a substantial impact on the ability of a country to export raw materials. In the case of phosphate, this was highlighted during the Arab Spring of 2010-2012. Tunisian production was in 2010 the 5th largest globally, but fell drastically after the revolution and resulting violence, lack of governance and rural displacement. Production in 2012 was just over a quarter of that in 2010 (USGS, 2013), and output still hasn’t fully recovered (USGS, 2018), with phosphate accounting for 10% of exports in 2010, and just 4% now (Amara, 2019). Similarly in Syria, where 40% of phosphate exports end up in the EU (ESPP, 2013), production fell from 3.5Mt in 2011 to zero in 2016 (USGS, 2013; 2018). This was a direct consequence of the civil war, and rise of ISIS, which took control of the Khanifish and Al-Sharqiya phosphate deposits (Kayali, 2018). Output may now be recovering, with 0.1Mt produced in 2018 (USGS, 2019). As the conflict draws to a close, it has been suggested that Russian trade with Syria will begin to increase significantly (Matveev, 2019), with phosphate playing a role in that relationship. It is understood that Russia gained a monopoly on Syrian phosphate mining after Russian militias expelled ISIS from the mines they had been occupying up to 2017. Kayali (2018) questions whether this takeover is a countermeasure to Russia’s potentially precarious position as Europe’s principal phosphorus supplier, due to the debate over Cadmium (see 3.2.3) which is present at lower concentrations in Syrian reserves than Russian.

As reserves become more concentrated, the political stability of those countries that are predicted to have a significant share of future output in the medium term needs to be considered. One such is Algeria (3rd largest reserves), where a joint project with China is expected to increase production at the Bled El-Hadba phosphate mine from 1Mt/yr to 10Mt/yr (Reuters, 2018). Another is Saudi Arabia, which began production in 2009 (USGS, 2013), and now has the 7th largest output. The country has invested in a vast new phosphate processing plant, although this has so far been underperforming (Jung, 2019). Although they avoided any major violence during the Arab Spring, both countries face significant internal difficulties. Recent political disruption in Algeria has been peaceful (Daraghi, 2019), but it remains to be seen whether a new government will be able to tackle a stagnating economy (Porter, 2019). Saudi Arabia, on the other hand, is usually considered to be relatively stable, but this has been questioned recently, with high youth unemployment and potential ruptures in the royal family (Stares and Ighani, 2017). It’s possible that exports from the Kingdom could form part of the growing competition between the Gulf states for influence in Africa, as a large part of future phosphorus demand will come from sub-Saharan countries (Todman, 2018). Interestingly, this may be used to grow food that returns to the Gulf, to counterbalance the lack of domestic food supply there, which sets up a food production loop highly reliant on the continuing flow of capital, that is not always guaranteed in unstable regions. These examples highlight the vulnerability of the phosphate trade to internal disruption, that often has wide-reading impacts on the economy and infrastructure. It is important to consider the potential for these conditions to arise when examining future supply.

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3.2.2.China

Between 2005 and 2015, Chinese phosphate production skyrocketed from 30 to 140Mt (USGS, 2009; 2019), and the country is currently by far the largest producer of phosphate. Since 2015, Output has begun to level off, albeit unevenly (USGS, 2019), with a variety of factors contributing to this slowdown.

Firstly, it’s likely the Chinese government is taking steps to draw out the lifetime of their reserves, which using current technology may only last until the middle of the century. This has been implemented most notably through a 135% hike in phosphate export tariffs in 2008 (Phosphate Futures, 2019), which was widely seen as a move to protect domestic fertiliser supply, as well as a method to force foreign companies to relocate their factories into the country. Although these were deemed unfair to free trade by the WTO in 2012, and are now reduced to zero for phosphorus rock (Bradsher, 2012; Argus, 2018), export quotas remain. Other smaller exporting countries may soon implement similar policies to preserve a domestic stockpile, which could lead to a global price increase (Kenkel, 2010). The recent trade war between China and the United States adds another dimension to economic and political supply disruptions, however most agree that tariffs have so far had little impact on fertiliser availability in either country, given the small quantities that are traded between them (PhosphatePrice, 2018). Nevertheless, according to the Independent Chemical Information Service (2018), the tariffs will have an impact on emerging economies like Argentina, India, and Turkey, which could stoke geopolitical tensions and limit cooperation on phosphorus sustainability.

There has also begun in China a major overhaul of environmental policies, with a particular impact on heavy industry. This includes phosphorus mining and processing, both of which have had considerable detrimental impacts on the landscape (Geissler et al., 2019). Rahm (2018) gives the example of Yichang City, with a mining capacity of 20Mt, as one area where wide reaching bans are being enacted on all industrial activity. One aspect of this has been the shutting down of operations below 0.15Mt (Wellstead, 2012b), which is argued to promote efficiency and make environmental protection easier, but can also lead to monopolistic behaviour, which in the long run is detrimental to markets. The International Fertiliser Organisation (IFA, 2018) forecasts a fall in phosphorus demand in China this year, as a result of more environmentally-conscious policies.

Lastly, it’s important to note that like reserve data, it is not always in the strategic interests of a country to release accurate production data. Chowdhury et al. (2017) point out that Chinese reserves dropped from 6,600Mt in 2007 to 4,100Mt in 2008. Given mine production in 2008 was steady at 50Mt, the figures are doubtful. This is especially counterintuitive as production continued to increase to 89Mt in 2012. There are still questions over how much China actually produces, with government figures citing 135Mt production in 2016 while Jasinski (2016) argues production may have been as low as 80-85Mt. Given a large proportion is consumed in China there is little reason for concern now, but in the near future when reserves begin to run out there will be a question over where the required phosphate will come from.

3.2.3. European Union

The EU depends on imports for 85% of its phosphorus supply, with most coming from Morocco (1.8Mt in 2017), Russia (1.6Mt) and Algeria (0.7Mt), making the food system as a whole heavily reliant on phosphate rock from abroad (Michalopoulos, 2018). Most of this phosphate is mined from sedimentary rock, which can contain considerable amounts of impurities, while 5% of phosphate globally is found in igneous rock, which doesn’t contain as many pollutants (Taylor, 2018). Only Russia, Canada, South Africa, Brazil, Finland and Zimbabwe are currently exporting igneous phosphate, making up 10-15% of production, despite the lower reserves (Walan et al., 2014). One of these impurities is the heavy metal cadmium, which the EU has recently been trying to impose restrictions upon, to remove it from the food system. In 2017 the EU Parliament adopted a proposal to do so but with an extended implication date. There will be an initial limit of 60mg cadmium per kg phosphate rock, with tighter restrictions coming in for 40mg/kg after 6 years and 20mg/kg after 16 years (Bourguignon, 2017). This could put a significant dent in the phosphorus security of the EU if sources are not diversified, or technology not developed, since if the full ban went ahead today, only 55% of currently imported phosphate would be admissible (Taylor, 2018).

As one of the few countries able to export igneous-sourced phosphate, which contains less cadmium, Russia is set to profit from an EU ban on high-cadmium phosphate rock and fertiliser, which would give the country significant political leverage over the EU, given the complete dependance on fertiliser for European food production. In fact, PhosphatePrice (2019) reports the satisfaction of PhosAgro’s board of directors in

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welcoming the EU’s new restrictions on cadmium, without mentioning that the company, which controls 15% of the European phosphorus fertiliser market, is based in Russia. It may be further argued that Russia is exerting pressure on Eastern European countries. Poland for example, as a large fertiliser producer, would be severely affected, with 70% of the country’s output containing cadmium beyond the 20mg limit (Michalopoulos, 2018).

The first question is how much of a health risk is the level of cadmium that is being discussed, which has bought up considerable debate, along with accusations of funding influencing research outcomes (Ulrich, 2018). This is unsurprising given that Zhang et al. (2008) estimate a 50% profit loss to the fertiliser industry to eliminate all cadmium contamination. Although it is certain that cadmium is toxic, on one hand Ulrich (2018) finds sufficient evidence in the literature that limiting cadmium is meaningful, while on the other, Roberts (2014) suggests phosphate fertiliser containing cadmium is safe, and limits would not have an effective impact in food safety. The second important question is whether the price of phosphate will rise enough to facilitate the removal of cadmium. The technology required to do so exists in a laboratory setting (see European Commission, 2016), but isn’t currently economically feasible at the industrial scale. The answer to both question is still not clear, but with politics, health, economics and technologically all interlinking it becomes a complex issue, and highlights the importance of the resource in global affairs. All the while, as high quality reserves are mined, impurities increase proportionally, and it is therefore likely that rock mined in the future will contain more cadmium than today.

3.2.4. Morocco

In the long term, if the global agricultural system is to continue its dependence on phosphate rock, the future hinges on Morocco. With the majority of reserves increasingly concentrated in North Africa, there are concerns over the ability of one country to have such an influence over global food production. Already, phosphates account for 18% of Moroccan exports by GDP (Yildiz, 2017), and production is expected to rise dramatically, increasing from 30Mt/yr to 52Mt/yr by 2026 (Jasinski, 2016). To achieve this, Morocco is revising mining policies, investing in infrastructure, and expanding international trade. The two factors to consider are how international power might shift to the country, and threats to the stability of continuing phosphate production, notably the decades-long Western Sahara conflict.

3.2.4.1. International Relations

Once reserves in other producing countries begin to become unfeasible, Morocco will likely gain a considerable amount of power on the world stage, and the country already has the ability to influence world affairs in its favour. One prominent example occurred in 2000, when India de-recognised the Sahrawi Republic (Western Sahara) after pressure from Morocco. According to a Wikileaks cable, 50% of Morocco’s phosphoric acid and 22% of phosphate rock went to India in 2009 (Huddlestone, 2019). It’s possible events like this will occur more frequently in Morocco’s favour, as the country can effectively use food security as a bargaining chip in international negotiations.

For this reason there is considerable interest in forming a relationship with the country. Major global phosphate consumers like the US are investing in Moroccan mines and processing plants, such as the Umm Wu’al phosphate mine of which Mosiac (a US-based company) owns 25% (Jasinski, 2016). The association with the US is strengthened by a free a trade agreement and development assistance (Elser and Bennett, 2011). Meanwhile, China has been extremely interested in Morocco as a part of the Belt and Road initiative, with extensive political, technological and cultural investment, the centre of which is a new city financed by China (Sherlock et al., 2018). Like many international partnerships, there is also a military aspect, and large military exercises with the US (Kasraoui, 2019a), or military cooperation with Pakistan (Xinhua, 2018) could be partially influenced by an objective to secure phosphorous supply, although there are many other possible factors.

3.2.4.2. Internal Vulnerability

Every increase in phosphorus production requires more to be spent on energy, and the 95% state owned mining group OCP consumes up to 7% of Morocco’s annual energy supply (Wagner, 2019). The need for energy ties phosphate production to global oil prices, and thus Morocco’s ability to power itself needs to be considered when exploring future output. Phosphate mining and processing is also highly water-intensive, and future requirements will partly be met by the expansion of the seawater desalinisation plant at Jorf Lsfar, increasing production from 25 to 40 million m3 (Takouleu, 2019). The reliable flow of fertiliser is therefore

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intrinsically tied to economic activities in other sectors, and with a complex supply chain comes more opportunities for disruption.

Structural problems within Moroccan society constitute a further factor to consider when exploring future output. Despite a strong economic forecast, with the IMF predicting 4.5% growth to 2024, unemployment has remained high, driven by automation, and a sustained dependance on agriculture. This is unlikely to be tackled by the highly mechanised mining and processing of phosphate. The situation is exacerbated by large disparity in access to services resulting from unbalanced growth, which has meant the gap between rich and poor is widening. Furthermore, agriculture still makes up a large part of GDP in Morocco, and an unstable climate can have a considerable impact, as in 2016 when a severe drought dragged down GDP growth to 1.1% (World Bank, 2017). Following from this, there is an ongoing debate concerning the impact of climate on conflict. El-Said and Harrigan (2014) note the influence of persistent drought in contributing to food riots and economic collapse in Morocco during the 1980s, and low income, agriculture-dependent communities have been highlighted as vulnerable to prolonged conflict resulting from climate change (FAO et al., 2017). Climate change is expected to have a especially major impact on North Africa, with temperature rises of 2-3 degrees expected by 2050 (Schilling et al., 2012). Coupled with a high population growth rate, and Morocco’s position as a hub for illegal migration from Africa into Europe (Teevan, 2018), there is a growing vulnerability to political disruption and internal conflict that could disrupt resource flows as happened in Tunisia.

This raises questions as to whether the supply shocks triggered by the Arab Spring discussed above could materialise in Morocco. Although not significantly affected by the Arab Spring, Morocco has seen strikes and protests over employment and wealth equity concerns, but has not experienced any major disruptions in phosphate production (Wellstead, 2012a). Nevertheless there are concerns, with a recent BBC article asking whether Morocco could be the next country of the Arab world to overthrow the government (de Castella, 2019). Furthermore, health concerns of miners that have resulted in strikes in Tunisia are gaining attention in Morocco (White, 2015). If similar strike action took place there would be a major issue for global phosphorus supply: Part of the reason for a lack of rebound in Tunisian phosphate production after the 2010 revolution is because of widespread strikes over working conditions. However, it’s important to note that these are only a few possible drivers of instability, that can combine with many others to create the conditions for serious social unrest. And lastly, political instability doesn’t always impact output, as seen in Egypt where phosphate production actually increased after the 2011 revolution, and wasn’t affected profoundly by the coup d’état in 2013 (USGS, 2016).

3.2.4.3.Western Sahara

A sixth of the reserves claimed by Morocco lie beyond its internationally-recognised border, in the occupied territory of Western Sahara (McTighe, 2013). This brings global attention to a longstanding conflict between Morocco, which claims sovereignty over the territory, and the Polisario Front, a Sahrawi nationalist group that declares its independence. Although the armed conflict ended in 1991, the territorial dispute continues (see Ojeda-Garcia et al., 2016), with Morocco currently controlling 80% of Western Sahara (Niarchos, 2018).

The Moroccan claim to the Western Sahara is not formally recognised by the UN or any state, however implicit support is given to Morocco every time a shipment of phosphate leaves the territory. Western Sahara Resource Watch (WSRW, 2018) provides annual details of Moroccan exports of phosphates from occupied territory, and in 2017 the largest importers were Canada, New Zealand, India and the USA. Meanwhile, some countries have recognised the Sahrawi Arab Democratic Republic, the most prominent neighbouring Algeria, which provides support to the Polisario Front, and accommodates thousands of Western Saharans living in Algerian refugee camps. Sweden and South Africa have also both shown affinity to the Polisario Front, the former calling out Morocco as an occupier (a term opposed by the Kingdom), and the latter seising a Moroccan shipment of phosphate from Western Sahara, and it handing over to the Polisario Front (Huddlestone, 2019). According to WSRW (2018), this resulted in three major importers ceasing to buy phosphate that originated from the territory. Beforehand, Mosaic had stopped buying Phosphate originating from Western Sahara in 2010, following Scandinavian banks divesting (McTighe, 2013). This was partially in response to the claims of statehood, as well as accusations of rampant corruption and human rights abuses within the territory.

The UN mission in Western Sahara doesn’t have a mandate to repot on human rights (Kasprak, 2019), and some, including former US National Security Advisor John Bolton, argue peacekeepers have prolonged the

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conflict (Huddlestone, 2019). Recently, Morocco has continued to make efforts to get on the good side of importing nations, including several Gulf States and the US, by very publicly cutting ties with Iran (Al Jazeera, 2018). In a potentially more relevant development, given the direction in which the centre of world power is gravitating, the Polisario Front has been excluded from the China-Africa forum in May (Kasraoui, 2019b). This is especially important as the conference is held by the African Union, to which Morocco has recently been re-admitted (Quinn, 2017), after being expelled over the occupation dispute. China and Morocco also signed memorandum of understanding in 2017, and taken together these events can be seen as a considerable lack of support for Western Saharan independence from the worlds largest phosphorus consumer.

If independence is won peacefully, it may not have a huge effect on the future of global phosphate, although it would diversify supply, which in turn reduces risk. However, if the conflict were to once again turn violent, or if a new state were to become destabilised, there would be a knock-on effect on phosphate flows around the world, with implications for price, accessibility to farmers and potentially food security.

3.3. Further Supply Questions

Phosphate production is highly water intensive, meaning water scarcity could limit output. Seeing as most production in the near future will originate in arid countries like Morocco and Saudi Arabia, water availability needs to be considered. In Morocco, groundwater levels have been falling since 1969 at a rate of 1.5m a year (UNEP, 2009). With increased water demand for crops as well, it is important to factor in this limitation. Furthermore, the process of phosphate production as a whole, from mining to processing to application, is heavily reliant on cheap energy, with high oil prices contributing to to the 2008 phosphorus price shock (Cordell et al., 2009a). Likewise, the transportation of phosphate rock and fertiliser products through our highly globalised production chains relies heavily on oil. Therefore, a future disturbance to the supply of energy or oil, driven by scarcity or geopolitical incidents, could have a knock-on impact on the availability of phosphorus (Walan et al., 2014), and with it fertiliser and ultimately food. Furthermore, increased oil prices will drive demand for biofuels, which puts pressure on food crops that will require more land, and so more fertiliser (Hein and Leemans, 2012).

One factor rarely mentioned in recent literature on the subject is the impact of climate change, and likewise climate change policy on the phosphorus system. There is considerable research showing that fertiliser productivity is dependant on soil moisture availability (Alexandratos and Bruinsma, 2012). This could have a range of impacts, either decreasing demand for phosphate as it becomes ineffective, or increasing demand as it becomes the limiting factor in plant growth. Either way, the impact on food security will be substantial. Climate change will make some areas of the world more arid, and they will cease to be able to support agriculture, yet it is also possible that other areas will experience enhanced precipitation and open up to farming (Sverdrup et al., 2011). While we have already ‘locked in’ a certain degree of warming for the future (World Bank, 2014), there is still time to reduce the environmental impacts if drastic action is taken immediately. Following from this, if we do adhere in any way to the emissions targets set out in the Paris agreement (UN, 2015), the policies that will have to be introduced on environmental protection, food consumption, and land use will have wide ranging impacts on phosphorus flows (see Ockenden et al., 2017).

Lastly, by examining production trends it can be seen that rock output is, as expected, closely linked to economic trends. Between 2008 and 2009 there was a global fall in production (USGS, 2013; 2006) tied to the economic crash, with particular reductions in Syria, Morocco, Jordan, Tunisia, Algeria, Australia, Jordan, Morocco, Russia and United States. Meanwhile at a national scale, Iraq was producing a considerable amount of phosphorus in the late 1980s, until UN sanctions hit in 1991, at which point production fell drastically, and in 2003 it was reduced to virtually nothing after the US invasion, a level maintained after the civil war began in 2014 (USGS, 2013; 2006). It follows that factors far removed from food production can considerably impact the availability of fertiliser, thus jeopardising the supply of food to an ever-hungry global population.

4. Drivers of Demand

In very near future, global annual production of phosphorus is projected to increase from from 47.0Mt in 2018 to 50.5Mt in 2022 (USGS, 2019). By far the greatest driver of this increase is rising fertiliser demand, to grow more crops, and feed more people. With more crops grown on the same land, a larger proportion of phosphorus is removed from the soil with the crops, and so more phosphorus is needed to replenish the soil after bumper harvests, such as between 2016 and 2018 (Rham, 2018). Yet in some regions, phosphorus

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demand has been falling. Fertiliser and manure application in Europe has decreased since the 1980s (Sattari et al., 2012) and in China, the world’s largest phosphate fertiliser market, demand dropped by more than 5% per year during the 2015-18 period (Jung, 2019). However, this has been offset by growing demand in Africa, Asia and Latin America. Here the impact of population and dietary shifts are explored alongside other factors that may contribute to shifts in global demand for phosphorus.

4.1. Population and Diets

Given that currently 90% of mined phosphate rock is used in fertiliser (ESPP, 2013), the main focus of demand forecasting is on the amount of crops grown around the world. This is driven ultimately by the number of people on the planet, the amount they consume, and their dietary habits. Estimates of future population growth vary, but have recently been predicted as 9.8 billion by 2050 (UN DESA, 2017). The pressing question is how food production will rise to provide for this extra 2 billion people when hundreds of millions are already hungry; we already use half the world’s vegetated land; and agriculture already contributes to a quarter of global green house gas emissions.

In the medium term, demand for food on a calorific basis is expected to come primarily from growing populations, rather than per-capita consumption (IFA, 2018; Files et al., 2018). According to the FAO (2009), under a continuing socio-economic paradigm overall food production needs to rise by 70% above 2007 levels by 2050. This translates to a food gap of 56% between crop calories produced in 2010 and what’s needed in 2050 (Searchinger et al., 2019). This increase in food production needs to be achieved while protecting natural ecosystems, reducing greenhouse gas emissions, and all without expanding agricultural land. Ultimately this means more phosphorus will be needed, as higher productivity usually requires more fertiliser (Alexandratos and Bruinsma, 2012).

On top of population, diets are changing considerably, with significantly more dairy and meat consumed every year, that requires more land, energy and water to produce. The increase in meat consumption of 58% in the 20 years up to 2018 (Whitnall and Pitts, 2019), has been driven equally by population growth and per-person consumption growth. Growing prosperity in developing countries, where higher incomes correlate to more meat consumption (Schroeder et al., 1996), will drive a sharp increase in consumption over the coming decades. In 10 years, meat production is expected to rise by 13% on 2018 levels (OECD/FAO, 2019), and in the longer-term, consumption is estimated to increase by 100% of 2005 levels by 2050 (Tilman et al., 2011). This estimate is based on the straightforward relationship between economic growth and the proportion of meat in a diet, but other studies use models of food system dynamics (e.g. Godfray et al., 2011). Valin et al. (2014) summaries these models to find meat consumption increasing by 62-144% by mid-century, with the FAO putting the figure at 76% (Alexandratos and Bruinsma, 2012). All in all, there will be a drastic increase, mostly coming from developing countries. The significance of this lies in the fact that a meat-based diet demands 3 times as much phosphate as a vegetarian (Cordell et al., 2009b), given the considerably greater crop requirements per-calorie for meat. However, the impact of meat consumption is not always taken into account in studies that estimate future phosphorus demand.

4.2. Further Demand Questions

4.2.1. Non-food Uses

The remaining 10% of mined phosphate has a variety of uses, including food additives, detergents, plastics, military applications, and livestock feed (Cordell et al., 2009b; Neset et al., 2016). Given the small proportion, this demand adds little strain, and the requirements of each can be expected to grow roughly in line with populations. One further use is in lithium-ion-phosphate batteries (Cordell and White, 2011), which are used in smartphones and electric vehicles. Although not the most common battery, the market is growing (Global New Wire, 2019), and the increase in demand for electrical vehicles means demand for phosphate may be stretched in the future, dependant on the speed in uptake of electric vehicles.

Further alternatives to conventional fossil fuel motors include liquid biofuels, which can come in the form of biodiesel, bioethanol, bio-oil and drop-in biofuels (Guo et al., 2015), of which there have been huge rises in consumption around the world. In the US for example, between 2000 and 2014 there was a 700% increase in the use of corn for bioethanol and a 10,000% increase in the use of soybean oil for biodiesel (Jarvie et al., 2015). Currently, 2% of global phosphorus is used as fertiliser for first-generation crops including sugarcane, wheat and corn. (Hein and Leemans, 2012). Following the predicted global shift away from fossil fuels, demand for biofuels is likely to increase in the future, and competition will continue to develop with food

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crops. The U.S. Department of Energy, for example, aims to replace 30% of fossil fuel transportation with biofuels (Ragauskas et al., 2006). The EU meanwhile, has a complicated relationship with biofuel policy, that started with a resolution in 2009 to increase the proportion of biofuels in all transport fuels by 10% by 2020 (Stattman et al., 2018). Since then, evidence has been presented that not all biofuels are as environmentally sound as once believed, and that in fact biodiesel derived from food crops can emit more greenhouse gases over its lifetime that conventional diesel (Marelli et al., 2015). This is once emissions due to indirect land-use change are taken into consideration, which represents the emissions from deforestation, as agricultural land is expanded to accommodate the food crops that biofuel crops have replaced.

Nevertheless, biodiesel production has been estimated to continue to rise. The EU is the largest producer and consumer (Marelli et al., 2015), although new sustainability criteria have recently been introduced (European Parliament 2018). If policies are introduced on the level required to meet climate targets, biofuels will need to make up a significant proportion of the worlds energy mix. The issue regarding phosphorus is that many crops for fuels are genetically modified, generally requiring more fertiliser inputs than some more traditional agriculture, which might be replaced, thus increasing demand. Hein and Leemans (2012) find that if current biofuel production continues to rise, the impact on phosphate depletion and so food security outweighs the gains from mitigating climate change for all biofuels except possibly sugarcane. This leaves a serious question over the feasibility of increased use of biofuels and the impact on land use, food security and phosphorus demand.

4.2.2. Waste and Distribution

A defining feature of sustainable systems is the elimination of waste. Currently, the journey nutrients take from mine to fork is extremely inefficient, and 80% of phosphate is lost from the point it is mined to the point it is consumed in foods (Cordell et al., 2009b; phosphorus Futures, 2019). With regard to the mineral phosphorus, Scholz and Wellmer (2019) find total nutrient use efficiency along the supply chain of 2 to 4%. The majority of phosphate losses are from diffuse leakages from agricultural land, which in the US accounts for 66% of losses (Suh and Yee, 2011). This happens primarily as not all phosphorus that is added via fertiliser is immediately taken up by plants, with only 15-30% reaching the crop (Roy et al., 2006). This leaves a significant excess, which can be amplified with pre-existing phosphate from weathered underlying bedrock (Sverdrup et al., 2011), and is therefore prone to being washed into waterways directly, or carried by eroded soil.

There are large imbalances in soil phosphorus content around the world, with many regions lacking sufficient phosphate, while others have surpluses. In many agricultural areas, poor management combined with limited knowledge or inefficient policies has led to great excesses of fertiliser being applied to the land, notably in India and many regions of China (Li et al., 2011). One cause of this is that many farmers will add manure based on the soils requirements for nitrogen, resulting in excessive phosphorus enrichment (Miao et al., 2011), which is present in varying levels in manures. Meanwhile in other regions various factors, including limited access to fertiliser markets, leaves the soil deficient in the nutrient. Vitousek et al. (2009) examine corn fields in Western Kenya, Northern China and the Midwest United States to find +1,+53 and -9 kg/ha/yr imbalances of phosphorus respectively. Rebalancing the mismanagement of phosphorus is a key aspect in the drive to a sustainable system, and while a significant amount of phosphorus waste can be recovered, Cordell et al. (2009a) note that it is more energy and economically efficient to prevent loss in the first place. Given the over-application in many countries, Mueller et al. (2012) estimate that phosphorus fertiliser application on maize, wheat and rice could be cut globally by 38% without impacting current yields. Huge numbers of farmers do not have access to phosphorus fertiliser due to economic scarcity, and close to a billion farmers and their families struggle to access fertiliser markets (Neset et al., 2016). Farmers in land locked African countries, for example, can pay 2-5 times more for fertiliser than those in European countries (Fresco, 2003). Jarvie et al. (2015) note that regions of poverty and food insecurity are often coincident with phosphorus deficient soils. Therefore it has to be considered what the impact might be on food, populations and the environment if phosphate fertilisers became more available in such countries where marginal land has the potential to be developed.

With humans consuming ever increasing amounts of phosphorus in their diets, and developments in technology and climate mitigation driving further demand, it is evident that a significant amount more phosphorus will be required in the coming years. Coupled with the risks to a stable supply outlined in 3, the world faces a point at which the continued provision of food may be threatened in the near future. Considering also the environmental impacts of continued unsustainable use, the phosphorus system can now

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be examined with the aim to increase resilience through certain critical points that could bring major change and improve system sustainability.

5. Points of Intervention

It is important that the world begins to take meaningful action towards a sustainable phosphorus system, as scarcity, and with it price rises, will occur much sooner than the point at which all recoverable resources are exhausted. This is even more urgent as many of the steps to achieve sustainability take a considerable time to implement (Cordell and White, 2011), and we have already far exceeded the planetary boundaries for nutrient balances. There are several points in the phosphorus system where policy intervention might create a path for desirable futures to materialise, centred around building resilience through diversifying supply and limiting demand. Chowdhury et al., (2017) provide further extensive examples of interventions in the phosphorus system, while national plans for phosphorus management have been reviewed by Ross and Omelon (2018).

5.1. Demand

5.1.1. Food

Phosphorus sustainability directly feeds into food security, and levelling out the extremes of over-eating and undernourishment plays a vital role in rebalancing phosphorus demand (Cordell et al., 2009a). This involves reducing the amount of food consumed in societies where obesity is a problem, while improving access to food in the poorest parts of the world. Odegard and der Voet, (2014) show that we will have the resources to feed the world in 2050, but it will require considerable shifts in the distribution of food, alongside major dietary change. To balance the food system, Searchinger et al. (2019) states that we need a combination of approaches, including increasing yields, reducing food waste, drastically reducing meat consumption, avoiding biofuel production, and improving women’s access to healthcare and education. It is also vital that any agricultural intensification is linked to the protection of natural ecosystems that provide invaluable services to human food production (Zhang et al., 2007). Together these actions can improve the sustainability of the food system, and in doing so contribute to stemming demand for phosphorus.

In more developed countries, one major opportunity to limit the need for phosphorus would be a reduction in meat consumption, and a global re-orientation towards flexitarian, vegetarian, or low-phosphorus diets is key in future scenarios that present any form of phosphorus sustainability. In fact, even an 80% closure of the yield gap would not sustain the ‘Western’ diet the world is moving towards (Odegard and der Voet, 2014). Although attitudes towards meat-eating in the developed world are changing, it is at much too slow a rate to make up for the growth in demand from the developing world. Wellesley et al. (2015) are among many to call for government intervention in the sale of meat, which could take the form of price interventions, support for innovation and promotion of choice, taxes, labelling and education. Although the backlash against this, especially in agrarian communities would be substantial. Theses policies are summarised by Marteau (2017) as possible interventions in the various conscious and subconscious processes that make up a choice to buy meat.

5.1.2. Agricultural and Food Chain Efficiency

Globalised food chains and an abundance of cheap food has lead to an enormous amount of food going to waste, estimated at a third of all food produced (FAO, 2019). The phosphorus going into the production of that food is also wasted, and so reducing food loss and waste can be an important pathway for conserving nutrients like phosphorus (Sage, 2011). Doing so depends upon tackling the loss of food in production and transport (most commonly associated with developing, agricultural countries) alongside minimising waste at the consumption stage (across all countries, but more so where food does not constitute a large proportion of household expenditure). The various pathways for reducing this waste have been explored extensively (Lipinski et al., 2013; FAO, 2019), and range from producing food closer to cities to encouraging better meal planning, leading to reduced global demand, and so reduced strain on phosphorus supplies (McConville et al., 2015; Drangert et al., 2018). Some food waste is nevertheless inevitable, and so to complement moves to reduced waste, unavoidable food waste must be composted for a fully sustainable system (Zhao and Deng, 2014), thereby returning unused phosphorus to the soil.

Meanwhile at the field level, discussions regarding agricultural efficiency compare yields to land area. Gains in this context have often come at the expense of phosphorus sustainability, as the foremost method to

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increase yields is the application of fertiliser. This thinking now has to be reconsidered in the context of providing more food while reducing fertiliser demand, by maximising yields per unit of phosphorus (Cordell et al., 2009a). This can be tackled in several ways, including improved timing of application, conducting more precise surveys prior to addition of fertiliser (Tóth et al., 2014), working on enhancing the chemical and physical properties of soil, and lastly ensuring sufficient microbial fungi, that allows root uptake of fertiliser. Key to these improvements is reducing the amount of phosphorus that is wasted on-farm, and minimising over-application. Limiting agricultural runoff and ensuring all the phosphorus applied is taken up by plants means farmers can apply less, and so demand is reduced. Currently however there is no fiscal incentive for phosphorus losses to be minimised at the farm level. This means that in developed countries, where access to phosphorus fertilisers is not a logistical or economic concern, it is cheaper to allow the phosphorus not taken up by plants to leach into waterways than implement management strategies to save it. Given that price rises are forecast to come too late to allow sufficient time to drive efficiency improvements, it is argued that government intervention is necessary (Cordell et al., 2009b). This can take the form of taxes or tax-breaks to encourage more sustainable fertiliser use, but as with much environmental policy, it is generally more effective to incentive improvements through subsidies than to make the polluter pay (Shortle et al., 2012). Through this farmers can be educated on the importance of environmental stability for the ecosystem services their crops require, and be supported in the financial cost of improving application methods.

Separate to these improvements in conventional farming is the potential of alternative, or traditional methods to take the place of high-intensity agriculture. Practices like organic farming, conservation agriculture and permaculture aim to reduce environmental stress by working with natural systems rather than artificially enhancing them. These are examples of farming systems where nutrient losses are minimised, reducing or eliminating the need for chemical fertiliser, and thus reducing demand for mined phosphate. Such farming has increased in popularity in recent decades as a response to the intensification of food systems, yet the feasibility of scaling these up to the world scale has been debated (see Fraser et al., 2016). Although phosphorus demand would be stemmed, widespread implementation of more sustainable systems remains a distant prospect all the while demand for food continues to rise.

5.2. Supply

As a fundamental element to all life, phosphorus exists throughout the world in many forms, and given the questions surrounding future supply of phosphate rock, there have been investigations into finding alternative raw sources. There has been some research into the potential to extract phosphorus from seawater and ocean sediments (Kimani, 2015) yet according to Walan et al. (2014), the technology is extremely unlikely to develop in the coming decades, and should not be relied upon to provide any substantial amount of the world’s demand in the near future. There remains some stock in more conventional sources, including algae and seaweed along with with ash and bone meal, but these will make up a small proportion of future supply, given their relatively low phosphorus content (Cordell et al., 2009a). Further sources include recovery from heavy industry, such as steel slag (Matsubae-Yokoyama et al., 2009), as well as the possibility of harnessing sludge from biomass digesters, which has a phosphorus content of up to 1.7% (Cordell et al., 2009a). Today, the price of phosphate rock is too low to spur development of these options, and so despite the options to diversify a country’s supply of the nutrient, and in so doing increase resilience, it is unlikely these will gain momentum without government incentives.

The potential for phosphorus recovery at different stages of the system has also been explored extensively (e.g. Mayer et al. 2016), but progressive action to ‘close the loop’ has been lacking. The main opportunities for returning phosphorus that would otherwise end up in the ocean or waste systems exist in better management of animal manure, human excreta, food waste and crop residue. Animal manure contains a large quantity of valuable nutrients, and poultry manure can be composed of up to 2.9% phosphorus (Roy et al., 2006). This manure represents a significant stock of the element that is not always returned to the agricultural system and therefore the fertilising properties are wasted. Globally, only up to 50% of the phosphorus contained in livestock manure is recycled into the agricultural system (Smil, 2000), and while this may never reach 100% because of the geographical distribution of livestock and arable land, there is certainly room for improvement (see MacDonald et al., 2011). One way to approach this would be increased integration of livestock and croplands (Tirado and Allsopp, 2012). Where this is not possible, there have been suggestions that manure could feasibly be transported to land with a phosphorus deficit (see Hanserud et al., 2017). By cycling phosphorus back into the system less will be required from phosphate rock. When including human excreta in addition to animal, Powers et al. (2019) map areas of the world where large human and livestock populations live in proximity to crop cultivation. They found manure-rich and populous areas that are near to

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cropland to be mostly in countries that are especially reliant on phosphorus imports, meaning there is great potential for phosphorus recycling to lead to agricultural independence and improved food security. Nevertheless, caution still needs to be taken to avoid the environmental problems associated with fertilisation as organic sources like manure have a much lower phosphorus content, and so have to be applied in larger quantities, thus there is a heightened risk of upsetting other nutrient balances (Johnson, 2017).

Humans produces 3Mt annually of phosphorus as excreta (Cordell et al., 2009a), with 10% currently redistributed to agriculture (Cordell et al., 2009b). There is scope for increasing this recycling, as phosphorus that passes through us can be retrieved directly from urine or from municipal sewage, where it can be extracted through incineration or struvite crystallisation (Zhang et al. 2017). However, Koppelaar and Weikard (2013) found that the cost of recycling phosphorus from wastewater was higher than any envisioned phosphate price, meaning the motivation will come from environmental concerns, rather than economic constraints. Nevertheless, one study found that if adopted unilaterally across Sweden, the recycling of human excreta could meet up 30% of Sweden’s phosphorus fertiliser demand (Kalmykova and Fedje, 2013). However, the finding is not universal. In Australia for example, even recycling 100% of phosphorus from all human excreta could only provide 5% of the country’s phosphorus fertiliser demand (Cordell and White, 2014). In countries with lower populations relative to the amount of cropland (in Sweden there is 0.26 hectares of arable land per person, while in Australia there is 1.93 (Trading Economics, 2019)), human waste would provide a lower proportion of the national phosphorus requirements. This highlights the need for focussed national policies on phosphorus sustainability. For example in Australia, Egle et al., (2014) find that combining phosphorus from municipal sewage sludge with bone meal could replace a much greater proportion of phosphorus required in fertiliser. For nearly all countries it is important to note that recycling will only reduce dependance on phosphate-rock based fertiliser, not replace it (Geissler et al., 2019), yet regardless countries are making progress, despite the lack of economic incentive. Germany for example, was the first country in the European Union to make phosphorus recycling from sewage water a legal requirement (Scholz and Wellmer, 2018), and Switzerland also has phosphorus recovery requirements (ETH Zurich, 2019).

5.3. Global Governance

Considering this combination of possible measures that can vary distinctly from country to country, alongside the overall complexity of the phosphorus system, there have been calls for a global management strategy to bring together actors in the drive towards phosphorus sustainability (Cordell and White, 2014). This is particularly import given the international cohesion that is necessary to coordinate conflicting policy, such as the question of how actions to prevent climate change will impact biofuel demand. Likewise, how agricultural decisions taken without consideration of the phosphorus system can have a negative impact on efforts to close the phosphorus loop. For example, in some developed countries, conventional ploughing is loosing popularity (Gregory-Kumar, 2016), and if fertiliser continues to be applied, phosphorus can accumulate on the surface and be washed more easily into waterways (ETH Zurich, 2019), leading to higher incidences of pollution.

Although there are platforms for sharing knowledge and promoting the sustainable use of phosphorus, including the European Sustainable Phosphorus Platform and the Global Phosphorus Research Initiative, there lacks an international institution that brings together governments, industry and sciences. This kind of global governance could take the form of an Intergovernmental Panel for Phosphorus Security (Childers et al., 2013), which would support research and be responsible for setting policy. Such an institution could also ensure accuracy and transparency in the reporting of reserves and production figures, including regular assessment of resources, possibly under a UN framework (Ulrich et al., 2013).

Overall, approaching the phosphorus question from both the supply and demand side shows the room for improvements in phosphorus sustainability. Limiting our dependance on high-phosphate diets and focussing on improved farming practices can go hand-in-hand with diversifying supply through manure and alternative sources. Together, there is a great deal that could be done to reduce reliance on rock phosphate, and through this is scope for improved global food security.

6. Scenarios

The potential for constraints on the phosphorus supply to materialise concurrently with increased phosphorus demand makes an exploration of possible futures highly relevant. Although scenario development is

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prevalent in questions of global sustainability, there are only a limited number focussed on phosphorus (see Cordell et al., 2009a; Van Vuuren et al., 2010; Neset et al., 2016). This is despite the essential place of the resource in the food-water-energy nexus (Jarvie et al., 2015) upon which humans survive, and the evidently devastating environmental impact of fertiliser use. In this section, a business-as-usual baseline projection is compared with three scenarios that explore the directions the phosphorus system could take in the future.

The baseline sees increasing demand meeting a slowly dwindling supply, as is suggested by the exploration presented above if no major changes occur in the phosphorus system. Following this, because of the growing understanding that tackling climate change will be the most important focus of the world’s resources in coming decades, the second scenario considers the impact on the phosphorus system if the world were to rapidly move towards ambitions climate policy. Next, the third scenario examines how geopolitical developments may constrain the flow of the resource around the world. And lastly, the steps that would need to be taken to rebalance the phosphorus system are evaluated in a scenario laying out what might follow a global shift towards phosphorus sustainability.

6.1. Baseline

A baseline scenario used by Bouwman et al. (2013) predicts future world development continuing to accelerate, with implications for people, food and phosphorus. This sets a world population of 9.4 billion in 2050, and economic growth of 3% in the period up to 2050, resulting in an increased per-capita food crop demand of 80% between 2000 and 2050. 70% of this is expected to be met by yield increases, with the rest from expanded cropland. Over the same period, Bouwman et al. (2019) estimate meat demand to more than double, with increased animal stocks in the form of intensified animal husbandry, and only limited increases in pasture land. It is likely that under increasingly globalised food chains and the impacts of climate change, spoilage and waste in the food system will increase in near future (Van Aalst, 2006). Likewise, if current consumption trajectories continue, the proportion of domestic food waste in the global commodity chain will increase in the future (Cordell et al., 2009a). Despite changing attitudes in developed countries with regard to composting, the concentration of future population growth in cities of developing countries makes it unlikely that relative rates of phosphorus re-use will increase without intervention. Taken together, these factors greatly increase demand for food, and it is clear that these developments will result in markedly amplified requirements for fertiliser. With no policy change, phosphorus demand is expected to increase by between 40% and 148% by 2050 based on 2007 levels (Metson et al., 2012; Van den Berg et al., 2016).

To deal with this rising demand under no policy change, yields per unit of phosphorus will need to improve, reducing phosphorus demand slightly in those regions where technology is accessible (Cordell et al., 2009a). However, this will not significantly offset growing demand for fertiliser. Grassini et al. (2013) caution that projections for yield increases based on the trajectory of the last 50 years need to consider that much of the celebrated gain was due to one-time innovations that cannot be reproduced. This means that it is increasingly difficult to make the breakthroughs in yields that the world has grown accustomed to, and has enabled such high population growth. On the supply side, as livestock production increases in line with meat demand, so does the availability of manure. This means that there may be increased opportunities for spreading phosphorus from alternative sources. However, the amount that might become available will not be sufficient to supply the higher phosphorus demand that the animals themselves require. The same is true for crop residues: increased crop production will increase the amount of residue available to the soil, but levels will rise proportionally to output, so the share of overall phosphorus supply from this source will remain the same.

In the near term, it is probable that global phosphate rock output will increase at a higher rate than demand. This is because unlike the cartel formed by oil-exporting nations, no such international cooperation yet exists between those countries that are exporting the most phosphate, and so competition will continue to keep prices low. The US and china, for example, are continually using commodity price mechanisms to gain an economic advantage at the expense of some export revenue. Meanwhile, the two countries with the largest reserves, Morocco and Algeria, are involved in a bitter dispute over Western Sahara. Therefore, instead of cooperating to maintain an agreed supply and keep prices high, such countries may over the next few decades ramp up production in an attempt to undercut each other, resulting in increased availability to low income farmers. With more fertiliser at hand, more crops can be grown and more people can be provided for, suggesting that in the near term food security based solely on fertiliser availability might be set to increase. The potential drawback of higher phosphate rock supply is that the incentive to reduce phosphorus waste in those regions where phosphors is economically scarce is eliminated, and even higher populations will be supported, which could magnify the impact of scarcity further down the line.

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In the longer term, all forms of scarcity will likely become more pressing. Countries will probably follow China’s lead in protecting national reserves, and so those without national stockpiles will suffer from the increasing concentration of phosphate rock reserves in North Africa. Without international action to preserve these resources and promote diversification, a point may be reached where phosphorus scarcity impacts the ability of the world to feed itself. First, as resources begin to dwindle and extraction becomes more expensive, prices will rise out of reach of many of the worlds poorest farmers. This would a have catastrophic impact on yields that have become reliant on fertiliser, and with that fall would come hunger and starvation in regions where phosphorus fertiliser sustains livelihoods. Food availability in the developed world may also be affected to some extent, but an equally impactful result would be the large displaced populations that come with social and economic disruptions. It can be assumed that eventually prices will facilitate extraction and recycling technology, that will increase supply. Alongside this, it would be ignorant to assume that no international action would be taken once the world arrived at a point where phosphorus scarcity was seriously impacting food availability. However, it is highly plausible that such measures will only come into effect once food supply in the developed world is threatened, given that to this day undernourishment persists throughout the world (FAO, 2013).

Taken together, these patterns suggest a world constrained by phosphorus availability arising sometime this century. The implications of such a scenario are worryingly evident in regions of the world already suffering from phosphorous scarcity and show themselves in the form of dramatically reduced harvests and food insecurity. It may be that the most severe impacts are limited to less wealthy countries, but because of the globalised nature of the food system, critical supply shocks in key breadbasket regions may limit food availability across the globe. In the developed world as a whole, dietary shifts may be forced as certain foods become more expensive, while among populations already affected by poverty, more dire results of food insecurity and malnutrition may become more prevalent.

Without any incentive for industrial-scale farmers to minimise phosphorus losses to the environment it is also likely that the environment will continue to suffer under business-as-usual. Although eutrophication is mainly seen as a limited problem affecting some sections of rivers or certain lakes, it is possible that there are unknown tipping points regarding nutrient balances in water bodies. This means that if current rates of leakage into waterbodies increase dramatically over the coming decades, aquatic ecosystems may shut down totally, with a devastating impact on all animal and plant life around the globe, especially the human communities that rely on freshwater and marine food sources. Overall, continuing as we are will likely put the world in a precarious environmental, economic and social position as phosphorus becomes increasingly scarce. Although technology and recycling may develop once prices facilitates them, without action to build a sustainable system, food availability will be highly vulnerable to geopolitical or climatic shocks, putting people at significant risk around the world.

6.2. Ambitious Climate Policy

Climate change has been argued as the single defining environmental problem that must be tackled if human development is to continue as we know it. However, despite international agreements like the Paris accords, there has been limited progress on the drastic scales that are needed to prevent total ecosystem breakdown (Plumer and Popovich, 2018). If the world is to make any significant progress on averting devastating and irreversible climate change, the global economy has to be rapidly re-orientated toward the single aim of cutting greenhouse gas emissions. The scale of change will have a deep impact on all sectors, and making up 11% of global emissions (Tubiello et al., 2013), agriculture will have a particularly important role to play. When looking at some proposed policies to reduce emissions, there is reason to believe that phosphorus sustainability can develop in line with radical change. However, there are others that could have an impact on the availability and movement of phosphorus around the world, with consequences for food security.

One of the most controversial aspects of emissions-reduction policy is biofuel. As discussed above, a growing demand for biofuels that require high levels of fertiliser may begin to infringe on the availability of fertiliser destined for food crops. Land given over to first generation biofuels will mean food cannot be produced on that land, immediately reducing global food production, if agricultural expansion is limited as it is under all climate mitigation scenarios. Phosphorus plays a part because if that land was used in another way, for example another climate mitigation technique like afforestation, chemical fertiliser would not necessarily be required. This means that by fostering the development of biofuel, driven by subsidies for low-carbon energy sources that is encouraged in much literature on future energy scenarios (IPCC 2019), fertiliser prices may be kept high (Van den Berg et al., 2016). While this may not have a direct impact in the

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developed world, high global phosphate prices can significantly impact the ability of low-income farmers to produce enough food, and so heavily impact food security.

While first generation fuels will still make up a fraction of total production, attention is moving to the use agricultural waste in the production of biofuel. This includes the harnessing of manure and crop residues for use in biodigesters (Achinas et al., 2016). At first this may seem a more sustainable alternative, however the technology comes into conflict with much of the literature on sustainable phosphorus use. It is precisely these byproducts of the agricultural industry that are proposed as fertilisers in a future world of limited phosphate rock (Cordell et al., 2009b). It is therefore likely that if biofuel use increases in line with ambitious climate targets, there will potentially follow a reduced availability of phosphorus in fertiliser, both chemical and more traditional.

A further strategy to minimise future carbon emissions is a heavy reduction in the consumption of animal products in the developed world. Limiting meat intake was presented as a method to stem phosphate demand above, but there is potential for such movements to have an adverse effect. Radically lowered meat consumption would lead to less livestock, and therefore less manure with which soils could be fertilised to reduce reliance on phosphate rock. While eating less meat will mean less fertiliser is required initially, there is already in many places a phosphorus deficit, which needs to be restored for soil systems to function efficiently. Furthermore, within some land restoration techniques livestock can play a role in maintaining ecosystem health (Sanderson et al., 2013), especially through digesting plant matter and therefore contributing to the soil nutrient stock. Therefore, a drastic limit of livestock, with more plant-based diets (Springmann et al., 2018) might not be able to provide enough fertilising material to sustain food crops, especially if phosphate rock availability is diminished.

Another key characteristic of the sustainable future presented in literature on climate change is the extremely high agricultural productivity needed to sustain rising populations. According to Mueller et al. (2012), targeted intensification, irrigation, efficient water management and elimination of nutrient imbalances could achieve 75% of attainable yields for major cereals. However, Van den Berg et al. (2016) note that efficiency gains that reduce phosphorus demand may be counteracted by increased demand to achieve agricultural productivity that comes with many ambitious agricultural efficiency scenarios. This would mean that in order to produce enough food, land is likely to be used more intensively. If not carried out sustainably, phosphorus deficits may develop that would have to be replaced by additional fertiliser, putting further strain on the availability of phosphorus, and with knock-on impacts on price, food, and ultimately malnutrition.

Conversely, a key aspect of limiting the impact of climate change will be an attempt to slow global population growth, which will naturally stem demand for food, fertiliser and phosphate rock. If this is achieved, it is possible that total climate disaster can be averted concurrently with reduced strain on phosphorus supply. There are other factors of ambitious climate policy that could impact phosphorus flows but are not fully explored here due to the ambiguity of the consequences. This includes bans on heavy industry to limit carbon emissions, which could have an impact on energy-intensive phosphorus mining and processing, as occurred in China. On the other hand, some repercussions of climate policy could be beneficial for soil phosphorus availability, and therefore ease pressure on global demand. In this category are the ecosystem services that could be enhanced through actions like afforestation. In some circumstances, these could have a restorative impact on soil properties, and reduce the need for chemical fertilisers. Overall, the requirements of ambitious climate policy will likely compete with phosphorus sustainability, but there is potential for the two to develop together if focus is placed on sustainable land management.

6.3. Geopolitical Disruption

The geographic distribution of phosphorus is more concentrated than virtually any other element, and it therefore occupies a particular position in global politics, side-by-side with resources like oil and rare-earth minerals, the control over which holds significant strategic importance. It is without question that global actors are considering the security of future phosphate supply as outlined in 3.2, and given the conflict that has played out around the world over control of resource flows like as oil, the potential for geopolitical disputes to impact flows should be considered. Considering that all countries except Morocco are likely to run out of economically-extractable phosphate reserves within 100 years (Cooper et al., 2011), reliance on the largest exporters will grow significantly over the coming decades. This dependence on a small number of countries leaves the phosphorus system vulnerable to supply shocks, and from a geopolitical perspective these could come in three forms.

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Firstly the threat of political disruption, that has been explored above, could materialise through a diverse chain of events and limit the ability of a country to export minerals. This could see regional disputes elevated to international conflict, as could be seen in the worldwide involvement in the Western Sahara controversy. Such a conflict always impacts those at the bottom of society most, and considering the value of phosphate reserves it isn’t unreasonable to assume resources would be dedicated to securing economic interests of each party. In this way it is possible that competition for control would lead to hostilities around deposit or processing areas, potentially halting production of phosphorus as was seen at Syrian phosphate mines. Taking the comparison with oil further, it might even be argued that global powers may become involved in a much more drastic shift through invasion or occupation with the goal of securing phosphorus flows. The immediate likelihood of this is nevertheless limited, but the implications for global food security may be worth exploring for a worst-case scenario. Conflict in particular may have a further exacerbated impact for two reasons. Firstly, the devastating result of upon agricultural landscapes has been well documented (Sivakumar, 2005; Baumann and Kuemmerle, 2016), and a reduction in the amount of land available for food production in one region will put strain on agricultural systems in other parts of the world. One way to relieve this would be to intensify production by using more phosphate-rock based fertiliser, and in so doing increasing the risk of environmental damage which it itself can lead to reduced ability to provide enough food. Secondly, conflict often leads to large displaced populations, who can put a strain on resources of the country or region they migrate to, and therefore amplify demand for food, and ultimately phosphate, in regions where supply may already be constrained. Susceptibility to conflict is increasing in line with climate change (Barnett and Adger, 2007), and so political events far removed from the phosphorus system may in the future drive supply and demand of the resource.

Secondly there is the risk of bans, tariffs and sanctions impacting the flow of phosphorus around the world. The likelihood of this uncertain, as few countries would be willing to limit access to phosphorus. However, in a case of high international tension certain countries may calculate that they are able to sustain national demand for a period of time, and thus enact trade restrictions on the flow of phosphorus to put political pressure on other nations. As discussed, the reliance on energy for the mining and processing of phosphate rock means that a restriction on oil and gas flows could have a similar impact.

Lastly, a significant threat to supply would be the forming of a cartel by the major exporting countries, like that of OPEC, which would be able to inflate prices for economic gain (Caldwell, 2009). The driver of this type of development would ultimately be a lack of international cooperation and transparency, which is not difficult to envisage continuing into the future. Already the world is divided, and the ability of international accords to bring about change to a system like that of phosphorus has been questioned (Clémençon, 2016), and can be exemplified in the failure to tackle climate change.

The result of one of these on global flows of phosphorus depends on the underlying trend in availbity. Today minor shocks can be buffered, but in a situation of global phosphorus scarcity, a limit on phosphate exports by the principal exporting countries would have a direct impact on phosphate price. This would materialise in a reduced availability of phosphate and a lower use of fertiliser, followed by a reduced soil stock and so limited plant production, eventually leading to higher food prices. Continuing this chain, food consumption would be impacted in low-income countries, where nutritional intake is highly reliant on a local crop, followed by malnutrition and a limit on population growth. Ultimately, this may have a balancing effect by reducing food demand, and therefore reducing phosphorus demand, which could in turn ease international pressure and release the geopolitical constrains on supply. A similar outcome of a sudden supply shock could also be observed through incorrect estimations of reserves, finance or energy crises, technological failures, natural disasters and violent conflict, all leading through the same cycle of reduced food security (Chowdhury et al., 2017).

6.4. Phosphorus Sustainability

This scenario places phosphorus resource efficiency above all other environmental concerns. Although this may seem far-fetched, nutrient flows are one of the important planetary boundaries that we are exceeding, and as outlined above, phosphorus is closely tied to many other aspects of the world ecosystem. The planetary boundaries are key elements of sustainability, that include greenhouse gas emissions, blue water use and biochemical flows, like that of phosphorus. Within the boundaries is a safe operating space for humanity, but beyond them ecosystems are at risk of loosing the functions upon which the world depends for human survival (Rockström et al., 2009; Steffen et al., 2015). It is therefore reasonable to present an image

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of what the most ambitious policy for stabilising phosphorus flows could look like, drawing on the points of intervention outlined in 5. Although climate change is now at the forefront of environmental concerns, it is only one aspect of the damage the current economic system is having upon the natural world. Carbon emissions must be tackled, but we cannot forget that concerns of soil degradation, water pollution, ecosystem collapse, and many others need continued attention. At the heart of these issues is consumption, and addressing it involves delving into the very framework of a society, which explains why the action presented here is a dramatic change of course.

The target for perfect resource efficiency would be to provide the 1.2g phosphorus required per-person per-day (EFMA, 2000) in the most sustainable manner possible, with minimal impacts on the environment and no wasted phosphorus. To achieve this Cordell et al. (2011) present a desirable situation in 2100 as projected business-as-usual demand reducing by two thirds, with the remaining supply comprising of a diverse mix of recovered phosphorus and phosphate rock. One key aspect will be the phasing-out of first generation biofuels (Springmann et al., 2018), to free up fertiliser to be targeted on food crops. However, the likelihood of this is doubtful, with climate campaigners much more prevalent on the global stage than those advocating a sustainable phosphorus system.

Much more concrete is the potential role of recycling to reduce demand. In a medium ambition setting for resource efficiency, Van den Berg et al. (2016) suggest recycling to include 25% of available phosphorus in 2030 and 50% in 2050. However, others argue this is not nearly enough, and Cordell et al., (2009a) propose that the maximum achievable proportion to be 90% of manure and 90% human excreta used as fertiliser by 2050. Further to this, Cordell et al., (2009a) propose 90% of crop residue to be ploughed back into the soil under a the most desirable situation. This means straw, husks and stalks would provide a proportion of the phosphorus content required by growing crops. Again, the practical feasibility of such high contributions is doubtful, especially when considering the current use of such by by-products in bedding, feed, fuel and roofing, and the substantial developments in waste infrastructure required globally. Further reductions are more likely to be achieved through cutting out food waste. For the world to align with the Sustainable Development Goals (UN, 2015), food waste should be cut in half by 2050. However, according to Parfitt et al. (2010), the maximum achievable reduction could see food waste reduced by three-quarters in the same time frame. By aiming to reduce food loss, these targets have the potential to drastically reduce the demand for phosphorus.

In terms of diets, a shift towards nutritional guidelines represents the kind of medium ambition change that would reduce phosphorus demand to a less vulnerable level. Such a diet would include a maximum of three 100g servings a week for red meat, accompanied by considerable reductions in calorific intake in the developed world (WHO, 2004; 2015). However, for phosphorus use to be cut to the extent that Cordell et al., (2009a) suggest is required, a more drastic reduction in animal product consumption is necessary. This could take the form of a flexitarian, plant-based diet, still in line with healthy eating, which would include only one serving of red meat a week, with many more nuts, legumes and vegetables (Springmann et al., 2018). How this change would come about is an important question. While there has been growth in the popularity of plant-based diets in many western countries (Forgrieve, 2018), opposition to changing diets remains grounded in many communities (e.g. Macdiarmid et al., 2016). In wealthier nations this is more straightforward, as recommendations are to a great extent in line with promoting good health. However in poorer parts of the world, implementing these guidelines would mean an increase in consumption of some high-phosphate food, increasing demand in this sector.

The impact of these changes would be far reaching. Reduced use of phosphate rock fertiliser could dramatically halt the environmental degradation outlined in 2.4, which is the main desirable outcome of this scenario. However, it is likely that by drastically reducing phosphate rock demand, prices will fall concurrently. The side effect of this is that without strong regulation the market will be exploitable to those unwilling or unable to reduce their usage of chemical phosphate, and may therefore increase application without regard for environmental matters. This process may be hindered if the price drops enough to restrict current extraction rates which may become economically unviable.

A further impact is that on jobs in phosphate-rock mining regions, which are often in countries where social support systems are not in place for the those seeking work. If rock production is dramatically scaled-back, there is a chance that the labour market will be unable to provide employment and those communities will find themselves in a precarious position. On a large scale this could cut a community’s ability to provide food and lead to a range of consequences including malnutrition, emigration and conflict. This is why it is important that governments are supported in evaluating the entire phosphorus production system and the

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knock-on impact of any changes. There is a concern that in the drive for phosphorus sustainability presented here, some social groups may be left behind in less democratic societies, where the voices of the marginalised are rarely heard. Nevertheless, recycling could open up markets in the circular economy, and the infrastructure required to achieve anywhere near the resource efficiency rates outlined would require significant investment and job creation, although not necessarily in those areas where miners are likely to loose their jobs.

7. Conclusions

The story of phosphorus is a complicated one, but its unparalleled position at the heart of the global food systems makes the understanding of the phosphorus system vital for approaching global challenges. This essay has attempted to present the key factors of that system in the context of constraints on supply and drivers of demand. These have been examined through specific case studies to highlight the fragility of phosphorus flows, and the importance of action to improve the system.

While many countries currently produce phosphate rock, the highly concentrated geographic distribution of reserves means one country, Morocco, will have significant control over the flow of phosphorus in the future, and therefore attention must be turned to the social, economic and political drivers of change in that region if the world is to continue to rely on phosphate rock for fertiliser. The argument put forward by many authors is that such continued reliance is unsustainable, and points of intervention to close the phosphorus loop have thus been examined as standalone policies, and in the setting of future scenarios. The question that emerges is less about the ultimate exhaustion of reserves, but more about how action in the near term can reduce reliance on a single countries exporting ability, while concurrently reducing the environmental issues that come with extensive use of chemical fertiliser. In all scenarios there is potential for disputes between actors, especially regarding the precarious situation in Western Sahara, and the need for openness and transparency in the phosphorus system has been highlighted. Considering the major changes that are needed to achieve any shift towards sustainability, global cohesion must be at the forefront of future phosphorus planning if conflict is to be avoided.

With a growing global population and limited land availability, the greatest challenge will be aligning food intensification policies to sustainable phosphorus use. This comes at a time of intense concern over climate change, and so possible contradictions between sustainable phosphorus policy and ambitious climate policy have been explored, highlighting the controversial topic of biofuel. Nevertheless, better phosphorous management overlaps in many cases with several targets for a more balanced world, including healthy diets and biodiversity protection. Effective policy should therefore work to reduce phosphorus demand while diversifying supply, and there exist many options to do so. Although significant cultural and economic barriers exist to implementing such policy, there is nevertheless great scope to achieve phosphorus sustainability and stabilise the global food system.

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