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Sustainability and veganism II: the environmental impacts of diet

According to a study by Oxford University, going vegan is the single biggest way to reduce your impact on the planet (The Guardian, 2019). Our current food system causes biodiversity loss (through deforestation of woodlands for pasture land), competition for land, water and energy with other industries, and greenhouse gas emissions (Peters et al., 2016). The impacts of the dairy and meat industries are well established – meat, dairy and fats account for the greatest land requirements in Westernised countries, which will only increase with demand across China and Indonesia (Peters et al., 2016; Figure 1).

Figure 1: Trends in per capita meat consumption. Source: Sabaté & Sorat, 2014.

The impacts of vegan diets compared to omnivorous diets is a bit of a hot topic at the moment, with many researchers looking into the potential environmental impacts of realistic diets (not just model diets or food groups, which are often studied). A UK-based study by Scarborough et al. (2014) looked at the impacts of different diets, focusing on the greenhouse gas (GHG) emissions attributable to each food type. They lend evidence to the statement that a diet including meat is worse for the environment than a meat-free diet, finding that an average 2000kcal high-meat diet had 2.5x the GHG emissions associated with it, compared with a vegan diet of the same caloric intake. The UK is a prime example of a Western country whose population generally eat a whole lot of meat: as such, the consumption of food accounts for 1/5th of all GHG emissions attributable to the UK. This is undoubtedly a substantial chunk of our GHG emissions, and demonstrates that higher meat consumption is bad news for our climate.

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A further study was conducted by Rosi et al. (2017), who looked at the diets of over 150 Italians, identifying themselves as either vegan, ovo-lacto-vegetarian (i.e. a vegetarian who also consumes dairy products and eggs) or omnivores. The impacts of these diets were measured in terms of carbon footprint, water footprint and ecological footprint, rather than GHG emissions, which gives a more holistic view into the type of impacts these foods can have. Aside from the predictable conclusion that the animal-based diet had higher scores in each environmental index compared with the other two diets, the study also suggests the importance of individual variability. For example, some members of the vegan group recorded a higher environmental impact than those of the other two groups as a result of what they were consuming, particularly high proteins and fats. Also of note is the amount of food a plant-based dieter consumes – because of the lower energy density of plant-based foods, the higher intake of food compared to vegetarians means that in some cases, there is no environmental benefit of going vegan compared to ovo-lacto-vegetarian (Rosi et al., 2017). This study is important as not only does it outline the importance of what kind of food you eat, regardless of diet, but how much you eat of each food. This is a vital consideration not only from a health perspective (see Sustainability and veganism I for that) but from an environmental perspective.

The environmental impacts directly associated with farming are only a slice of the whole range of effects our food industry has on the environment. For this reason, there is growing interest in the concept of life-cycle assessments for food products, which look at each step in the growing, manufacturing, fertilising, transporting and selling of goods. One such assessment completed by Reijinders et al. (2003) found that the average complete life cycle impacts of a non-vegetarian meal is up to 2x higher than a vegetarian meal. Furthermore, processed protein sources based on soybeans, account for up to 17x less land use, 20x less fuel usage and 26x less water usage compared to meat protein. This more integrated approach to assessing environmental degradation (not just focusing on emissions) gives a more holistic picture into the impacts of agriculture, in terms of pollution, air miles and pest control. They also highlight yet more issues to consider with the food you eat (yay!).

Any diet can comprise local, organic, exotic or highly-processed foods. As previously mentioned, it is these production and transport methods wherein a lot of environmental damage can occur. When factoring in for these effects, unexpected outcomes might arise – for example, Reijinders et al. (2003) found that long-distance transport of vegetables can equal or surpass the CO2 emissions of the same amount of organic meat:

“long-distance air transport of 1 kg food has roughly the same environmental impact as the primary production of 1 kg organic meat. So vegetarian food flown in by plane may well be at an environmental disadvantage if compared with locally produced organic meat” – Reijinders et al. (2003)

Furthermore, the consumption of “exotic” vegetarian goods which have high CO2 emissions accompanying their transportation, or vegetables produced in fossil fuel-heated greenhouses, may mean that certain components of a plant-based diet have a higher impact on the environment than locally sourced, organic meat (Reijinders et al., 2003).

These studies demonstrate that you cannot pin all environmental issues associated with food production on the meat industry. The problem is not as simple as just considering emissions, either, but every stage of the life cycle of the food you are tucking into. Of course, decreasing the amount of meat can be the first step to a more sustainable diet. By cutting out the “middle man” of cattle, people can directly consume the crops (soy and grain) which would have fed them. In fact, if the 16 major crops grown in the world were prioritised for human consumption only, there would be a 28% increase in food availability (Sabaté & Sorat, 2014). But don’t let this distract you from scrutinising the methods used to produce the food you consume: deforestation for arable land, eutrophication of water sources and the excessive use of non-renewable minerals such as phosphates (in fertilisers) are all problems associated with agriculture, regardless of your diet type.

To summarise then, Sabaté & Sorat (2014) give a nice conclusion regarding sustainability and diet:

“At the current trends of food consumption and environmental changes, food security and food sustainability are on a collision course. Changing course (to avoid the collision) will require extreme downward shifts in meat and dairy consumption by large segments of the world’s population. Other approaches such as food waste reduction and precision agriculture and/or other technological advances have to be simultaneously pursued; however, they are insufficient to make the global food system sustainable.” – Sabaté & Sorat, 2014

In order to look at individual food items and their impacts (specifically GHG emissions and water usage), I suggest looking at the wonderful climate change food calculator provided by the BBC.


Peters, C.J., Picardy, J., Wilkins, J.L., Griffin, T.S., Fick, G.W., & Darrouzet-Nardi, A.F. (2016) Carrying capacity of US agricultural land: Ten diet scenarios. Elementa: Science of the Anthropocene4(1), p.1.

Reijnders, L. & Soret, S. (2003) Quantification of the environmental impact of different dietary protein choices. The American journal of clinical nutrition78(3), pp.664S-668S

Rosi, A., Mena, P., Pellegrini, N., Turroni, S., Neviani, E., Ferrocino, I., Di Cagno, R., Ruini, L., Ciati, R., Angelino, D., & Maddock, J. (2017) Environmental impact of omnivorous, ovo-lacto-vegetarian, and vegan diet. Scientific reports7(1), p.6105

Sabaté , J. & Soret, S. (2014) Sustainability of plant-based diets: back to the future. The American journal of clinical nutrition100(suppl_1), pp.476S-482S

Scarborough, P., Appleby, P.N., Mizdrak, A., Briggs, A.D., Travis, R.C., Bradbury, K.E. & Key, T.J., (2014) Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK. Climatic change125(2), pp.179-192

The Guardian (2019) The 14 things you need to know before you go vegan. [online] Available at: (Accessed: 23/11/2019)


Published by avleveri

Hi! I'm Anna, an environmental science graduate from the UK. My main interests (if you can't already tell from my blog posts) are sustainability, consumption, conservation, nutrition, fitness and food! Lots of food.

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  1. A really well written and thoughtful article! It would be interesting to see what impact livestock that are fed on food waste or on grazing land that isn’t suitable for crop growth would have on the sustainability of farming them. A great read!



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