‘Food sustainability’ has become a critical issue in the agricultural and environmental sciences and public health nutrition in the context of population growth, rising obesity levels, climate change and the environmental degradation that occurs as a consequence of the modern food system(Reference Tilman, Cassman and Matson1–5). The food and nutrition system is defined as(Reference Sobal, Khan and Bisogni6):
the set of operations and processes involved in transforming raw materials into foods and transforming nutrients into health outcomes, all of which functions as a system within biophysical and socio-cultural contexts. (p. 853)
Human and natural resources form the basis of the food and nutrition system, but technology, policies, economics, education, socio-cultural trends and research also affect the way the food system operates(5). Traditionally, nutritionists have been expert in their understanding of the role of nutrients in human health, but they also need to consider the broader context of human health, which also encompasses planetary health(Reference Gussow7, Reference Wahlqvist8). Health and nutrition professionals require a solid understanding of the environmental, social and health impact of our current food system, because health risks to populations arise from physical and cultural landscapes and from the impact that man has on environmental assets and systems(Reference McMichael9).
The aim of the present paper is to examine the real cost of food to the environment and population health, predominantly in the Western world, in the interest of conciseness. It begins by tracing the historical development of the modern food system, including a discussion of power relationships within this system. The paper then outlines the impact on the environment and evaluates the social and health costs that are the unintended consequences of this system. Finally, the paper considers current knowledge of the ways in which local food systems can mitigate the environmental, social and economic impact of our current food system that may also improve people's nutritional health and argues that public health nutrition can make a valuable contribution to this emerging literature.
Upstream influences on the current food system
Globalisation
The current global food system faces major challenges in being able to produce sufficient food for a growing world population that addresses the economic, environmental and social imperatives of sustainability. In the last four decades, the modern industrialised food system has been extremely successful in achieving a doubling of world food production, which has kept pace with world population growth(Reference Tilman, Cassman and Matson1, Reference Pretty3). However, these increases have not been uniform across the globe. It seems extraordinary that there are in excess of 800 million people who go hungry, mostly in the developing world, while there are others suffering from chronic disease as a result of overconsumption(Reference Pretty3, Reference Tilman10, Reference Ikerd11). Much of the growth in obesity and chronic disease is now occurring in developing countries undergoing a ‘nutrition transition’, where consumption of foods high in fats and sugars is rising, driven by urbanisation and globalisation, replacing traditional starchy, high-fibre staples(Reference Hawkes12, Reference Popkin13). With global population projections at 50 % higher than the current 6 billion people by 2050, the demand for grain is expected to double, owing to expected increases in per capita real income and further shifts in dietary patterns that will include more grain-fed meat(Reference Tilman, Cassman and Matson1).
To achieve high production rates, agriculture became more mechanised from 1930 onwards, which led to reliance on finite stores of fossil fuels to run large machinery, pumped irrigation systems and produce artificial, nitrogen fertilisers(Reference Pretty3, Reference Horrigan, Lawrence and Walker14, Reference Kirschenmann15). With increasing mechanisation has come larger farms and fewer farmers(Reference Pretty3, Reference Lawrence16). In an attempt to gain production efficiencies, farmers now grow specialised crops, such that four main grains – barley, maize, rice and wheat – occupy nearly 40 % of global cropland(Reference Tilman10).
Power and politics in the globalised food system
The industrialised food system that has given rise to these increases in production and inequities has been developing for centuries, but it has been since the Bretton Woods conference in 1944, where Western leaders designed a new economic and financial structure, that a new era of global food trade started to emerge. Three supranational institutions – the World Bank, the International Monetary Fund (IMF) and the General Agreement on Tariffs and Trade (GATT) – were established to facilitate economic growth and trade across the world. The World Bank supported projects that encouraged a global trading system, such as huge, centralised energy plants, long-distance transport networks and advanced communication systems. The IMF's role was to impose a standard economic framework for all nations and GATT worked towards ensuring that all countries depend on world trade by removing barriers to trade. In 1994, member nations of GATT created another governing body, the World Trade Organization (WTO), to set trade rules and settle disputes between nations(Reference Norberg-Hodge, Merrifield and Gorelick17).
However, it is the wealthy industrialised nations that benefit most from globalisation(Reference Kutting18, Reference McMichael19). Large transnational food companies, often based in the global north, wield the most power in WTO negotiations(Reference Kutting18, Reference McMichael19). Their sheer capital base and use of horizontal and vertical integration strategies, whereby smaller, similar types of companies are purchased, as well as complementary ones, allow them to control the entire food system and dominate world markets(Reference Lawrence and Grice20). Agricultural restructuring in recent decades has also meant that retailers and food manufacturers increasingly determine what farmers grow, providing strict specifications of their requirements in contractual arrangements, leaving farmers with less control over what they produce(Reference Lawrence and Grice20). Supermarkets are also exerting greater control over the food production sector, by manufacturing their own ‘private’ label products, often sourcing cheaper raw ingredients from overseas sources, rather than locally(Reference Burch and Goss21).
Consequences of the current food system
Food as a commodity
As illustrated above, the modern, globalised food system trades food as a commodity, just like any other product in the marketplace, so linking food production to a particular place which has cultural significance to a population rarely occurs(Reference Pretty3, Reference McMichael19). In parallel with this phenomenon, people are encouraged to think that their food comes from multinational companies rather than from farmers and the earth, which has resulted in an acceptance of an anonymous and homogeneous food supply that has contributed to the rise in diet-related diseases across the globe(Reference Pretty3, Reference Popkin13, Reference Caraher and Coveney22, Reference Klein23).
Intervening outcomes of the current food system
Environmental costs
The industrialised farming practices that have been tailored to achieve maximum productivity for economic gain have led to a myriad of inadvertent environmental costs(Reference Tilman, Cassman and Matson1, Reference Pretty3, Reference Kirschenmann15, Reference Conacher and Conacher24). Approximately half of the global usable land is used by pastoral or intensive agriculture, but through land degradation, there is now a steady decline in arable land worldwide(Reference Tilman, Cassman and Matson1, Reference Horrigan, Lawrence and Walker14). In countries such as the USA and Australia, where programmes to improve soil erosion have been implemented, the impact of soil erosion is still high(Reference Kirschenmann15, 25). Other factors impacting on soil quality are acidity and salinity, both of which impair plant growth(Reference Mason26).
The modern agricultural system affects water resources. First, it diverts water from other potential uses, such as for domestic, industrial, recreational and environmental purposes(Reference Tilman, Cassman and Matson1, Reference Horrigan, Lawrence and Walker14, Reference Ginns27, Reference Pretty28). Second, agriculture reduces water quality, through pollution by high use of fertilizers and pesticides and through increased sediment and salt loads that occur as a result of soil erosion and salinity(Reference Tilman, Cassman and Matson1, Reference Beeton, Buckley and Jones4, Reference Horrigan, Lawrence and Walker14, Reference Conacher and Conacher24). Somewhere between 30 % and 50 % of nitrogen fertilizers and approximately 45 % of phosphorus fertilizer is taken up by crops, leaving the remainder somewhere in the environment(Reference Tilman, Cassman and Matson1, Reference Conacher and Conacher24).
Australia's ecosystem is not very resilient to external pressures and as a result of extensive land clearing for agricultural purposes and overgrazing, biodiversity is in serious decline(Reference Beeton, Buckley and Jones4, Reference Sattler and Creighton29). Industrial agriculture also favours using a narrow range of crop species, replacing multi-strata vegetation and complex crop patterns(Reference Vandermeer30), which leads to a loss of structural diversity and causes the fragmentation of native habitats and consequently a decline in animal populations, especially invertebrate consumers, predators and pests(Reference Horrigan, Lawrence and Walker14, Reference Chappell and LaValle31–Reference Matson and Parton33). Monocropping also relies heavily on the use of artificial pesticides to avoid disease and pest damage to crops, which further reduces biodiversity, as they kill wild bees and other species that are not necessarily the target organisms(Reference Horrigan, Lawrence and Walker14, Reference Johnson34). Many of the genetically uniform high-yielding crop varieties commonly used in modern agriculture are often less resistant to pathogens and pests, making them susceptible to attack by new or adapted parasites, which threatens the sustainability of the current food system(Reference Heller and Keoleian35, Reference Margosian, Garrett and Huchinson36).
The final way in which modern industrialised agriculture affects the environment is through its contribution to climate change(Reference Beeton, Buckley and Jones4, Reference Horrigan, Lawrence and Walker14, 37). According to Intergovernmental Panel on Climate Change estimates, agriculture contributes about 10–12 % of human-generated greenhouse gas emissions globally(Reference Smith, Martino and Cai38). Energy use from fuel and electricity also contributes to greenhouse gas emissions from the agricultural sector(Reference Smith, Martino and Cai38). Beyond the food production section of the modern food system, the carbon emissions that are generated through transportation of food also present challenges for the current food system. The term ‘food miles’ is a proxy measure for the distance that food travels from paddock to plate, but in fact, the impact of food transport on the environment depends largely on the type of transportation(Reference Saunders, Barber and Taylor39). For instance, carbon emissions generated from food transported by boat are nearly four times lower than the carbon emissions from food transported in large trucks(Reference Saunders, Barber and Taylor39). Purchasing locally can reduce the distance that food travels, but these gains may be offset by the smaller trucks used and lower load factors(Reference Estrada-Flores and Larsen40). Further, the carbon emissions generated by consumers driving to and from food outlets can be greater than those generated from the food production and distribution phases of the system(Reference Foster, Green and Bleda41). Hence, from a purely environmental perspective, local food systems may not significantly reduce emissions from transport, unless very-low-carbon transport systems are used(Reference Larsen, Ryan and Abraham42).
Social and economic costs
Apart from these environmental costs, the social costs of our current food system are also significant. The success of farms and food businesses depends on people working together for a common purpose, which depends on the civility of society(Reference Ikerd11). Social capital is described by Putnam as the quantity and quality of social relationships, civic participation, norms of reciprocity and trust that exist in a community, which have traditionally been high in rural communities(Reference Putnam43, Reference Lawrence44). However, the food system as it functions today weakens personal relationships between farmers, and between farmers and food processors and retailers, because of its competitive nature(Reference Ikerd11, Reference Renting and Van Der Ploeg45). Australian farmers, who once prided themselves on upholding the significance of family and community obligations and being committed to rural life, are now more individualistic in response to economic rationalism(Reference Lawrence44). To survive financially, farmers have had to sacrifice long-term sustainability for higher productivity because they are competing on world markets, making it difficult for farmers to stay viable in the industry(Reference Lawrence44, Reference McMichael and Lawrence46). Further, with a depressed agricultural economy, supporting rural industries also struggle to survive, leading to a decline in the size and vitality of rural communities and, with it, diminished social capital(Reference Conacher and Conacher24, Reference Lawrence44). In concert with these circumstances, the globalised food system has meant that urban dwellers have become physically and socially separated from farmers(Reference McMichael19) and disconnected from nature, with little knowledge of the way that food is produced(Reference Pretty3).
Food and nutrition costs
The impact of the current food system on non-farming families, the urban consumer, is not so direct, but equally insidious. The literature from the USA provides a comprehensive illustration of the disturbing intermediate outcomes of the globalised food system for food and nutrition. The estimated average adult energy intake in the USA in the 1970s was 10·07 MJ/d, but by the turn of the century this had increased to 12·16 MJ/d(Reference Swinburn, Sacks and Ravussin47). Between 1970 and 1996, there was a 22 % increase in the amount of fats and oils in the food supply, and a 23 % increase in consumption of sugars and sweeteners(Reference Kantor48). High-fructose corn syrup (HFCS), a cheaper alternative to sucrose, now represents 40 % of caloric sweeteners in food and beverages following a 1000 % increase in its consumption between 1967 and 1990(Reference Bray, Nielsen and Popkin49). A diet high in HFCS may actually encourage overconsumption through mechanisms that cause a reduction in insulin and leptin release, hormones that inhibit food intake, which may be contributing to rising obesity levels(Reference Bray, Nielsen and Popkin49). Over the last decade, there has been a doubling of the number of fast-food restaurants in the USA(Reference Powell, Chaloupka and Bao50) and sales through restaurants are expected to reach $US 604 billion in 2011, representing a 14-fold increase since the 1970s(51). In a recent study, 30 % of an adolescent sample reported eating fast foods on a typical day and those who consumed fast foods had higher energy and total fat intakes, drank more sweetened beverages but less milk, and ate fewer fruits and non-starchy vegetables than those who did not consume fast food(Reference Bowman, Gortmaker and Ebbeling52). Energy-dense fast foods may also undermine people's normal satiety mechanism and induce passive overconsumption(Reference Prentice and Jebb53).
System outcomes of the current food system
Obesity and chronic disease
In 2005, there were 1·6 billion overweight people over 15 years of age and a further 400 million people who were obese, according to global estimates, with projections that there will be 2·3 billion overweight people and 700 million obese by 2015(54). Recent figures show that nearly three-quarters of the adult population in the USA is classified as being above the healthy weight range(Reference Ogden and Carroll55). In Australia, between 1995 and 2007/8, there was growth in the proportion of people who were overweight or obese, from 64 % to 68 % for men and from 49 % to 55 % for women(56). Diet-related diseases accounted for the highest mortality and morbidity levels in Australia in 2007, and they were among the top seven disease groups that accounted for nearly half of the health budget for 2004/5(57).
Food insecurity
Research from both the USA and Australia has found that there are more fast-food restaurants in lower- than higher-income neighbourhoods(Reference Powell, Chaloupka and Bao50, Reference Thornton, Bentley and Kavanagh58). It is cheap, energy-dense foods that are preferred by those who are food insecure, because these foods supply more energy for each dollar spent, but too much energy is consumed, and excess weight results(Reference Drewnowski and Specter59). Food retailing has changed over the past four decades, such that large supermarkets, which often provide a greater variety of fresh food more cheaply than smaller corner stores, are less accessible without car transport(Reference Guy, Clarke and Eyre60–Reference O'Dwyer and Coveney62). This change in the food retailing environment has led to the development of ‘food deserts’, places where people experience both economic and geographical barriers to accessing healthy food(Reference Guy, Clarke and Eyre60, Reference O'Dwyer and Coveney62, Reference Beaumont, Lang and Leather63). Despite large supermarkets often offering a wider range of healthy foods, neighbourhoods with a larger number of small grocery stores may be better designed for walkability and social interactions, which may have other positive health benefits for residents, and should be considered in finding comprehensive solutions to food insecurity(Reference Moore and Diez Roux64).
An unsustainable food system
Hence, this globalised food system that promotes competitiveness, devalues personal relationships, discourages connections with nature and with food producers and imposes substantial environmental, social and health costs cannot remain sustainable(Reference Bambrick65, Reference Feenstra66). None of the environmental costs that come from the production and transport of food are included in the cost of food for the consumer. It will be up to future generations to pay for these hidden externalities of our current, ‘efficient’ agricultural production methods(Reference Pretty3, Reference Norberg-Hodge, Merrifield and Gorelick17, Reference Wilkins67). The most disadvantaged in our communities will be the most vulnerable to these price pressures, so solutions must ensure that current inequities are not exacerbated.
Local food systems
There is some preliminary research on the role of local or community food systems in improving food system sustainability(Reference Brodt, Feenstra and Kozloff68–Reference Kirwan71), but whether community food systems can adequately address the environmental, social and health costs of the global food system is not so well established. A local or community food system is defined as(Reference Feenstra66):
a collaborative effort in a particular place to build more locally based, self-reliant food systems and economies – one in which sustainable food production, processing, distribution and consumption is integrated to enhance the economic, environmental and social health of a particular place. (p. 100)
Local food systems are not necessarily designed to completely isolate themselves from trade, but rather they aim to adapt local food production and markets to suit the environmental and health priorities of a community(Reference Feenstra72). They form a viable counter-movement to the globalised food system in which local ecology, culture, trusting relationships and access to healthy food thrive(Reference Kirschenmann15, Reference McMichael19, Reference Gillespie and Smith73). Local food system models include farmers’ markets, community-supported agricultural enterprises (CSA), roadside stands, box schemes, pick-your-own enterprises and community gardens(Reference Wilkins67, Reference Feenstra72, Reference King74, Reference Pretty and Hine75). CSA are a relatively new concept, having originated in Japan and Switzerland in the 1960s and designed to share the risks and benefits of food production between the farmer and the consumer(Reference Hawkins, Davies and Hawkins76). Community gardens may be an allotment garden, where individuals have ownership, or shared spaces, where the food production is pooled among the community(Reference Bartolomei, Corkery and Judd77).
Intervening outcomes of local food systems
The early discourse on the role of these local food systems came from academics reporting on their observations and interpretations of current activities in these spaces, rather than from empirical evidence(Reference Pretty3, Reference Wilkins67, Reference Feenstra72, Reference Peters78). The common themes discussed are that local food systems provide access to nutritious food for all; they help to develop bonds between farmers and their customers; allow community members to more actively participate in the food system and contribute to social cohesion; encourage satisfying social and cultural interactions around food; develop social responsibility and stewardship of local land; support biodiversity; and enhance a community's economic vitality(Reference Pretty3, Reference Wilkins67, Reference Feenstra72, Reference Peters78).
There is some evidence from local food system research that supports these views(Reference Brodt, Feenstra and Kozloff68–Reference Kirwan71, Reference Sharp, Imerman and Peters79–Reference Wakefield, Yeudall and Taron84). Farmers are motivated to join these systems for many reasons, not least of which is the desire to counteract the power of the dominant globalised food system and to model a successful, alternative community food system(Reference Wells, Gradwell and Yoder70, Reference Kirwan71, Reference Sharp, Imerman and Peters79). Other motivations include improving farm diversity, producing fresh, nutritious food that is often organic, reducing ‘food miles’ and building relationships with customers(Reference Wells, Gradwell and Yoder70, Reference Sharp, Imerman and Peters79, Reference Cox, Holloway and Venn80, Reference Griffin and Frongillo85). In turn, customers are motivated to participate in local food systems to purchase fresh, organic and seasonal produce, support farmers and build trusting relationships with them, and enjoy the social interactions that take place(Reference Perez, Allen and Brown69, Reference Kirwan71, Reference Cox, Holloway and Venn80, Reference Feagan, Morris and Krug81, Reference Archer86, Reference Szmigin, Maddock and Carrigan87). One of the few studies to examine any nutritional benefits for users of local food systems found that participants reported eating more and a greater variety of vegetables and prepared more home-cooked meals than prior to joining the CSA(Reference Perez, Allen and Brown69).
To date, there is a good understanding of the motivations of those selling and purchasing from local food systems, which includes a desire to reduce the environmental impact of food systems, but full life-cycle analyses of foods sold through these systems are needed to quantify any changes in carbon emissions that can be attributed to them. It is also unknown if those who procure food from these systems use low-carbon transport systems, such as walking, bikes or public transport. Understanding whether the social connections that occur between consumers and farmers through local food systems increases people's appreciation of food, encourages more thoughtful and healthier food choices and reduces food waste could provide important clues to finding better environmental, social and health outcomes for communities.
System outcomes of local food systems
While many of the food system projects demonstrate the interrelationship between food system sustainability and food security and the value of a just and equitable food system(Reference Feenstra72, Reference McCullum, Desjardins and Kraak88), much of the literature indicates that the demographic groups involved in acquiring their food through CSA and farmers’ markets are those of mid to high socio-economic status, with some exceptions(Reference Perez, Allen and Brown69, Reference Wells, Gradwell and Yoder70, Reference Cox, Holloway and Venn80). There is a danger that some local food systems may become exclusive and inward-looking, providing niche markets for expensive foods, sometimes labelled ‘yuppie chow’, rather than a type of local food system that focuses on equitable food access and community food security(Reference Feagan, Morris and Krug81, Reference Hinrichs89, Reference Winter90). McCullum and colleagues(Reference McCullum, Desjardins and Kraak88) outline a myriad of opportunities for improving community food security, which includes linking community gardens, farmers’ markets and CSA to emergency food relief programmes, but it is unknown how often these opportunities are taken up. One such project, the ‘Field to Family Community Food Project’, an extension of a CSA, incorporates marginalised, low-income families into the broader community through their inclusion in the weekly CSA food distribution and cooking groups, but only CSA producers were interviewed and not those who are members or shareholders of the CSA(Reference Wells, Gradwell and Yoder70). The views of low-income families about the role CSA and other local systems play in improving social inclusiveness and access to healthy foods are critical to establishing whether local food systems are effective in achieving equity(Reference Allen91) and reducing the gap in health outcomes between rich and poor(Reference Baum92). Public health nutritionists can play a key role in helping to design and implement local food systems that are more inclusive of all social groups.
A conceptual framework has been proposed to discuss two parallel and sometimes intersecting local food systems, which are classified as contemporary and traditional localism(Reference McEntee93). Traditional localism may occupy the same physical space, but a different social space to contemporary localism. Traditional localism is usually associated with community gardens or home gardening, where healthy and affordable food can be obtained. Contemporary localism is usually manifested through farmers’ markets, CSA and food cooperatives, and is concerned with freshness, support for farmers and a place to exercise commitment to sustainability issues(Reference McEntee93). Perhaps, given the extent of overweight and obesity globally and the detrimental environmental, economic and social effects of the current globalised food system discussed earlier, allowing these two types of localism to coexist, provided all social groupings have their needs met, will achieve more to mitigate the environmental effects of the food system and improve the nutritional and social health of communities than trying to contrive a one-size-fits-all local food system. After all, essential to the establishment and maintenance of local food systems is active participation by citizens in helping to shape the food system to their requirements, which is described as ‘food citizenship’ or ‘food democracy’(Reference Lang94–Reference Hassanein96). Public health nutritionists can have an important role in encouraging all people to become food citizens and in advocating for more democratic food systems, so that decisions relating to the food system are not left to large, corporate interests.
The globalised food system and nutrition-related health outcomes: an explanatory framework
Finding solutions to the obesity epidemic by modifying the current food supply to provide less fat, sugar and salt, legislating for tighter regulation of food industry marketing and offering lifestyle modification educational programmes are all legitimate(Reference Swinburn and Bell97), but there may be untapped opportunities within local food systems to achieve equivalent or possibly better outcomes. Figure 1 provides a framework to explain the associations between the current globalised food system and poor nutrition-related health outcomes and direction for future research. The darker arrows indicate where the links between upstream influences on the food system and downstream system outcomes are well established in the literature. The lighter arrows indicate what is not known or where little evidence exists for the links between concepts proposed. The body of literature linking the upstream end of the food system through to the intervening outcomes is solid, as summarised in the present review. However, it is unknown whether the disconnections with nature and between farmers and consumers (intervening social and economic outcomes) affect people's food choices and subsequent levels of obesity or not. It is also unclear whether social connectedness may improve food security and food system sustainability, even though equity of access to healthy food is a well-understood critical component of socially sustainable food systems(Reference Allen91). These are important relationships to understand, as closer social connections between people in the food system may influence positive food behaviours and health outcomes in ways previously unexplored.
Fig. 1 The current food system (GHG, greenhouse gas)
Local food systems: the pathway to food sustainability and improved nutrition-related health outcomes?
Similarly, Fig. 2 offers a conceptual framework to explain the links between local food systems and food system sustainability, food security and obesity. The evidence that local food systems are less detrimental to the environment than the current food system is still not clear. Organic products are common in these systems, but not exclusive(Reference Kloppenburg, Lezberg and Master98, Reference Lea99), and it is unclear whether their production and distribution systems mitigate carbon emissions(Reference Foster, Green and Bleda41). Motivations for using local food systems focus on the procurement of healthy, fresh food(Reference Kirwan71, Reference Cox, Holloway and Venn80, Reference Feagan, Morris and Krug81), but the evidence that better eating habits ensue is scarce. There is some support from the community garden literature that local food systems address inequities and provide solutions to food insecurity(Reference Bartolomei, Corkery and Judd77, Reference Saldivar-Tanaka and Krasny83, Reference Armstrong100), but this is less clear in other local food system literature(Reference Hinrichs89, Reference Winter90). In fact, as discussed earlier, some local food systems may engender power differentials between social groups, but the evidence is somewhat insubstantial. These are important areas for public health nutrition researchers and practitioners to become engaged with, to ascertain which local food systems can best improve current inequities, eating habits and health outcomes and to advocate for optimal local food system models.
Fig. 2 Local food systems (GHG, greenhouse gas)
Conclusions
The modern industrial food system produces an abundance of cheap food, but there are very costly consequences of this system for society, the environment and health. Current research indicates that local food systems may offer social, environmental and health benefits, but public health nutrition researchers need to more clearly establish the links between use of local food systems and better eating habits and reductions in obesity and chronic disease. In the interim, public health nutritionists can play a key role in supporting people to become food citizens and to advocate for democratic and sustainable food systems.
Acknowledgements
The author is part of the Faculty of Health in her working capacity as a Senior Lecturer in Nutrition and Dietetics, but for the purposes of the present paper is part of the Faculty of Education, as this is the department in which her supervisor resides. The paper has been generated from the author's PhD work and there was no funding for it, other than generous in-kind support from supervisors from the Faculty of Education and the University of Canberra. This paper is an original work and it has not been published previously, nor has it been submitted to another journal for publication. There are no conflicts of interest to report. Special thanks to the two reviewers for their thoughtful feedback and to Dr Helen Berry for her helpful suggestions regarding the re-structuring of this manuscript. Also thanks to Leigh Blackall for his technical support with the diagrams.
