By A. Clare
Introduction:
Sustainable food systems form a core part of the European Green Deal, which aims to tackle the climate and environmental challenges currently faced by our planet. As discussed in part 1, many studies on dietary carbon impacts focus on the generation of emissions within the farm gate but neglect to include those generated during the upstream and downstream processes. Environmental impacts of diets extend beyond the generation of greenhouse gas (GHG) emissions. The availability of resources in areas foods are grown is also an important consideration.
Deforestation:
Deforestation produces GHGs (especially through burning), destructs habitats and results in loss of species and biodiversity (FAO, 2017). Livestock farming, particularly cattle, is often stated to be the primary cause of deforestation around the globe. Since 1978, approximately one million km2 of the Amazon rainforest has been destroyed (Butler, 2020) and, this is often put down to the intense land requirements for cattle farming (Greenpeace, 2020).
In the UK, cattle are raised on land deforested centuries ago and; therefore, GHG emissions linked to deforestation are avoided (Committee on Climate Change, 2020). Nevertheless, the consensus that eating meat is the primary cause of deforestation still exists. However, the agriculture and livestock sectors do not exist in isolation because the rearing of livestock on deforested lands acts as an intermediate step in crop production (WWF, n.d). This integrated farming system provides the soil with adequate nutrients - in the form of manure - to enhance plant production and enable more edible crops to be planted (WWF, n.d). Although integrated farming systems are not an excuse for deforestation, it is inaccurate to assume that deforestation results from the meat industry alone.
Deforestation due to some plant-based crops is globally recognised; however, the extent of this recognition often depends on media coverage. For example, in 2018, the negative environmental impact of palm cultivation was acknowledged across the globe. Palm oil is in many supermarket products and, its high demand continues to be a major driver of deforestation in many parts of the world (WWF, 2020). The consensus that cattle farming drives deforestation arises from the ‘snapshot’ the media portrays. Similarly, the rising demand for avocados in recent years has caused many Mexican forests to be destroyed to clear space for this valuable crop (Barisimantov & Antezana, 2012; Cho et al., 2021; Häberli, 2019). However, the lack of media coverage on this topic means that avocadoes continue to remain a key component of many plant-based diets.
The environmental impacts relating to the increasing demand for soy have also recently been recognised. The US, Brazil and Argentina make up approximately 80% of soy production (2017 data), with production in South America doubling between 1960-2014 (Voora et al., 2020). This intense soy cultivation has resulted in Amazon deforestation. Soybeans have become an essential protein source in many diets because they are rich in essential amino acids. Soy is also commonly used to replace protein in meat alternatives, with consumption of these novel protein foods increasing in the UK (Archer, 2019). The UK meat alternative market is projected to grow by 6.8% in the next 4-years (The Vegan Society, n.d), which will likely further increase the demand for soybean cultivation.
Bryant et al. (2019) state that 91% of Amazon deforestation is due to the land requirements for animal feed. The perception also exists that livestock competes with humans for food (Capper et al., 2013) and that if everybody ate a plant-based diet, we would need 75% less farmland than we use today (Greenpeace, 2020; Springman et al., 2016). Approximately 75% of soybean crop production (by weight) is used in livestock feed (Voora et al, 2020; WWF, n.d); however, this statistic is often misleading. Table 1 demonstrates the raw materials used in GB animal feedstocks in 2017. Soybean cake and meal comprise only 8.4% of livestock feed production, demonstrating that the GB livestock sector is not intensely dependent on soya products for animal feedstuff. Furthermore, soya cake and meal are produced as by-products during the extraction of soybean oil (Moura et al., 2015).
Table 3 – Raw materials used in GB animal feedstocks in 2017 (DEFRA, 2018)
Soybean oil is of high value and accounts for over 25% of global vegetable oil production (Franjee & Garnett, 2020). During oil extraction, soybeans are crushed to produce oil (approximately 20% by weight) and a solid residue (approximately 80% by weight), known as ‘cake’ or ‘meal’, depending on the extraction method (Franjee & Garnett, 2020). After processing, 99% of soybean oil is intended for human or industrial use, whereas 99% of cake/meal is used in animal feed (Franjee & Garnett, 2020). Soybeans can also be used without processing, with 6% used directly in human food and an almost equivalent 7% used in animal feedstuff (Franjee & Garnett, 2020) (Figure 1).
Figure 2 - The use of soybean and its derivatives (adapted from Franjee & Garnett, 2020).
Although by weight, 75% of soybean production is used for animal feed, most of this is produced as a by-product during oil extraction. Due to the meaty texture, a small proportion of soybean cake/meal can be processed into plant-based meat alternatives (Franjee & Garnett, 2020); however, as mentioned in part 1, highly processed meat alternatives often have a larger carbon footprint. Because soybean oil and cake/meal originate from the same bean, their uses are mutually and economically dependent on each other. Even if the UK did highly depend on soy cultivation to feed its livestock, as soybean cake/meal is a by-product of oil extraction, it is unfeasible to put soy deforestation down to one cause.
Land Use Area:
Competition for Food between Livestock and Humans:
The perception exists that livestock and humans compete for land to grow food supplies (Greenpeace, n.d; Springmann et al., 2016). For example, PETA suggests that “the world’s cattle alone consume a quantity of food equal to the caloric needs of 8.7 billion people” (PETA, n.d). As discussed, the extraction of soybean oil produces a by-product, which, unless it undergoes intense industrial processing, is often inadequate for human consumption. The redirecting of by-products to livestock feed is not a new practice (Truong et al., 2019). Livestock diets are often supplemented with waste products that help reduce the GHG emissions wasted during food production, and the emissions associated with the direct production of livestock feedstuff (Truong et al., 2019).
Many cultivated crops are not suitable for human consumption due to unpalatability, safety, quality or cultural considerations and, these are often fed to livestock (Capper et al., 2013). Unpalatability arises because energy is often contained within cellulose, which is indigestible to humans (FAO, 2018). Bacterial fermentation within ruminants enables the digestibility of cellulosic materials (Capper et al., 2013) and; therefore, these forages are often given to livestock to reduce waste and improve the carbon footprint of food chains. Without livestock in this process, GHG emissions from food waste would increase. Furthermore, there would be drastic increases in the demand for agricultural land because a high proportion of unpalatable material means that crops used for human food are characterised by yields far lower than those fed to livestock (FAO 2019a).
UK Land Types:
It is often proposed that a reduction in livestock production would significantly decrease land use (Capper et al., 2013; Stehfest et al., 2009). However, this statement assumes that the land used to rear livestock is suitable for producing human-edible crops (Capper et al., 2013). As previously mentioned, livestock are farmed on areas of marginal land where no other crops could be grown (FAO, 2019a) and; this is particularly evident in the UK - where the climate is unsuitable for growing a diverse range of fruit and veg. Agricultural land makes up 56% of the UK (Alasdair, 2017), with 65-77% of this composed of grasslands (FAO, 2018; NFU, 2019a). Although grasslands are suitable for grazing animals, they cannot always be used for crop production without the use of livestock as an intermediate step (FAO, 2018; NFU, 2019a). Although the adoption of integrated farming systems has enabled 27% of UK land to be suitable for crop production, 82% of these crops are dominated by cereals and oilseed (DEFRA, 2017), further demonstrating the low diversity of crops that can be grown in the UK.
Biodiversity Impacts:
The European Commission (2020) states that “the increasing recurrence of droughts, floods, forest fires and new pests are a constant reminder that our food system is under threat and must become more sustainable and resilient”. High ecosystem resilience results from high biodiversity (Erisman et al., 2016) because a highly diverse ecosystem is essential to allow adaption to environmental change (Jones, 2017). The definition of biodiversity considers two components; richness (i.e., the number of species in an ecosystem) and evenness (the extent to which species are evenly distributed).
Agriculture is recognised as the primary driver of biodiversity loss globally (Pereira et al., 2012; Sala et al., 2000; Zabel et al., 2019). Expansion of cropland production can threaten biodiversity through loss and fragmentation of natural habitats (Chaplin-Kramer et al., 2015; Foley et al., 2005; Zabel et al., 2019), which disrupts food chains and results in declines of many species (European Commission, 2020). Over 6000 plant species are cultivated for food; however, less than 200 species substantially contribute to the global food output, with only nine species contributing to 66% of total crop production in 2014 (FAO 2019a). During crop production, single species are cultivated over large areas, which leads to widespread habitat homogenisation (Zabel et al., 2019). Cropland production also threatens biodiversity through high fertiliser, herbicide, and pesticide inputs, which are applied to land to save labour and increase crop yields (Benton et al., 2003; European Commission, 2020; Kleijn et al., 2009; Zabel et al., 2019).
Habitat heterogeneity results from diversity in habitat types and vegetation structures (FAO, 2019a). The species diversity within heterogeneous habitats tends to be greater if areas are subject to moderate levels of disturbance. Ecological disturbance can be natural (e.g., floods, fires, grazing) or human-influenced (e.g., deforestation, ploughing). Although ecosystems can benefit from moderate disturbance levels, human-influenced disturbances that are incorrectly managed can also contribute to a reduction in biodiversity (FAO, 2019a).
Intermediate levels of disturbance can increase the biodiversity of an ecosystem by reducing the dominance of the most competitive species and allowing alternative species to become established. The worlds livestock production is limited to approximately 40 species (FAO, 2019b) and, although livestock farming has the potential to be environmentally damaging, the grazing behaviour of livestock can also positively influence biodiversity in many grassland habitats (FAO, 2019b; Watkinson & Ormerod, 2001). The ecological niche (i.e., the role an organism plays in an ecosystem) of livestock reared in extensive farming systems is similar to wild herbivores (FAO, 2019b). Livestock grazing exerts a medium level of disturbance on ecosystems - increasing biodiversity by changing the physical environment and the availability of resources and substrates.
The importance of biodiversity to food security and sustainable development is widely recognised. Due to the low species representation in both livestock and crop production, any further global homogenisation in diets is likely to decrease biodiversity further; through an increase in species abundance and a reduction in species richness (Figure 2). The impact of diets on biodiversity has been demonstrated by Jones (2017), who demonstrated that 19/21 studies showed an increase in species richness with an increase in the number of food groups consumed. The link between the diversity of diets and ecosystems is also demonstrated in nature. For example, on coral reefs, high diversity is maintained by the presence of generalist feeders with high trophic versatility (Bellwood et al., 2006).
Figure 2 - Diet diversity relative to species diversity.
Water Footprints:
Sustainable utilisation of water resources is critical for improving food security across the globe (FAO, 2019a). Water footprints measure the amount of water withdrawn from a source to be used. Water usage differs from water consumption, as the latter refers to the amount of water actually used and not returned to its original source. A water footprint is composed of blue water, green water and grey water. Blue water; is water sourced from surface (i.e., rivers and lakes) or groundwater resources, whereas green water is sourced through precipitation or collected through evaporation. Alternatively, grey water is water that has been used by humans and is available for re-use.
The type of water used depends on location and currently available resources. Withdrawing water from areas facing extreme water scarcity can have pronounced consequences. Agriculture is the largest user of water globally, accounting for approximately 70% of all blue water withdrawals (FAO, 2015). Excessive use of blue water can contribute to water stress, which occurs when water demand exceeds the available amount (Environmental Agency, 2016). Water stress is currently affecting at least 17 nations, often occurring in areas with low rainfall and high population density (Environmental Agency, 2016). Water stress can sometimes be a seasonal phenomenon and; therefore, its variability is likely to increase with climate change (United Nations, 2021).
The UK has a total water footprint of 102 Gm3 per year, with 73% (74.46 Gm3) of this allocated to agricultural products (Chapagain & Orr, 2008). The green water footprint of agriculture refers to the production water requirement met through rainfall (Hoekstra, 2012). The use of green water for agriculture is often more sustainable than using blue water (Aldaya et al., 2010), because green water can only be used on natural vegetation or rain-fed crops and, therefore, it does not compete with other uses (Aldaya et al., 2010; de Fraiture et al., 2004).
The Water Footprint of UK Livestock:
UK livestock agriculture has a water footprint of 29 Gm3/year (28% of total UK water footprint). Minimal meat imports mean that the internal water footprint for UK livestock is greater than the external water footprint (Chapagain & Orr, 2008). Bovines are known as being very water-intensive and comprise the majority of the livestock footprint in the UK. The production of 1 kg of beef requires approximately 17,000 litres of water; however, due to the high amount of rainfall in the UK, 84.4% (14280 l/kg) of this water is green (NFU, 2020).
Soil structure is determined by the level and flow of water in soil (Lundqvist & Steen, 1999), which is affected by the amount of organic matter. Organic matter in the form of cattle manure positively impacts soil properties, improving water filtration rate, water holding capacity and soil hydraulic conductivity (Rayne & Aula, 2020). These improved properties prevent green water from recharging groundwater (i.e., prevent it from becoming blue water) (Rayne & Aula, 2020) and, therefore, water remains in its most renewable source.
The Water Footprint of Fruit and Veg:
The water footprint of UK crop agriculture is 46 Gm3/year (45% of total UK water footprint) and unlike livestock, the external water footprint of crops is greater than the internal (Chapagain & Orr, 2008). The larger external water footprint results from the importing of “virtual water” within foods (Water Footprint Network, n.d). Importing virtual water from countries facing extreme water stress can significantly impact the environment, the economy and human health.
Nuts (e.g., cashew nuts, almonds and walnuts) are among some of the most water-intensive crops produced across the globe (Poore & Nemecek, 2019; Vanham et al., 2020). Cashew nuts require 45,914 litres of water per kg of nuts produced, whereas almonds require 12,080 litres/kg (Vanham et al., 2020). Almond milk is one of the most popular dairy milk alternatives; however, 1 litre of almond drink requires 158 litres of blue water to produce, relative to 8 litres of blue water required for 1 litre of dairy milk (NFU, 2020).
Avocados are also very water-intensive, with a single avocado requiring between 140-272 litres of water (Frankowska et al., 2019). Furthermore, avocados trees require constant irrigation due to their relatively shallow roots (PIRD, 2019). Avocados are often grown in countries that are facing a water crisis. In 2018, avocado trees in Cape Town continued to be irrigated, despite the area experiencing extreme water loss (Häberli, 2019). Similarly, the UK sources the majority of its avocados from Peru (Norman & Waite, 2017), where the trees are irrigated from groundwater sources (Häberli, 2019).
Heavy over-exploitation of aquifers in Spain has negatively impacted water quality and quantity, resulting in declining water tables and negative impacts on biodiversity (Chapagain & Orr, 2008). Imports from Spain represent 3% of the UK water footprint due to products such as olives, grapes, oranges and rice (Chapagain & Orr, 2008). Similarly, many water-containing products are imported from Morocco (e.g., grapes, citrus fruits, strawberries) and Pakistan (e.g., rice, mangos and chickpeas), which contributes to increased competition for water resources in these areas (Chapagain & Orr, 2008). Mangos imported from Pakistan are very water-intensive, requiring 686 litres of water per kg, which is extracted from the ground during warmer months (Chapagain & Orr, 2008). All the countries mentioned above are classified as water-scarce.
Conclusion:
Sustainable food systems are critical for protecting our environment whilst continuing to provide resources to our growing population. Any product produced on an industrial scale and; therefore, every type of food production has an environmental impact. Although the generation of GHG emissions is important, they only form part of the wider sustainability picture. The release of emissions during livestock farming, particularly cattle farming, should not overshadow the alternative environmental impacts that can arise from plant-based diets. A sustainable plant-based diet is often promoted, but the location-specific impact of this diet along the entire supply chain is rarely discussed. A sustainable dietary choice should consider how and where food was grown, the environmental pressures involved in its production and the local resources available.
Although agriculture globally is a net contributor to GHG emissions, it is important to recognise how different production systems contribute to food production in places where other types of farming are not practical. The definition of a ‘sustainable diet’ should be adapted depending on where you are located and what your locally available resources are.
Take a look at part 3 of this article, which discusses the importance of social and economic aspects when making a sustainable dietary choice.
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