Multiple studies have proven it--going vegan is the smartest decision you can make to help protect our planet. In fact, in the most comprehensive study to date, researchers at the University of Oxford looked at nearly 40,000 animal farms across 119 countries and found that dropping meat and dairy reduces an individual's carbon footprint from food by 73%--and would reduce global use of farmland by 75%! They also discovered that while meat and dairy production is responsible for 60% of greenhouse gas emissions from agriculture, the products themselves provide just 18% of calories and 37% of protein levels.
After completing the study, lead author Joseph Poore concluded that 'A vegan diet is probably the single biggest way to reduce your impact on planet Earth, not just greenhouse gases, but global acidification, eutrophication, land use and water use.'
In fact, eating vegan makes a far more positive impact than giving up your car!
What about eating local? When it comes to environmentally-friendly eating, studies have found that we should focus more on what we eat, not where it comes from. Transport makes up less than 10% of the overall emissions associated with agriculture; in fact, when it comes to products like beef and lamb, it makes up only 1%. The same rule even applies to meat and dairy which are produced more sustainably as a result of their location. The vast majority of plant-based foods simply have a lower impact upon our environment.
What about organic animal products? Research has found that the environmental cost of organic meat production is just as high as that of conventional production. For beef and lamb, the impact is about the same; for chicken, it is slightly worse, and for pork, it is slightly better. But even organic pork is eight times more impactful than the highest impact conventionally-grown plant foods! 
'If we had a mostly plant-based diet we could increase the yield of the land. We have an urgent need for land. [...] Half of fertile land on Earth is now farmland, 70 per cent of birds are domestic, majority chickens. We are one-third of animals on Earth. This is now our planet run by - and for - humans... If we continue on our current course the damage will be eclipsed by the damage that comes next.'
Sir David Attenborough
Unlike the majority of plant-based foods, raising 70 billion animals annually requires vast amounts of water. Animals need water to:
drink and to wash
for cleaning their living spaces
to cool them during hot periods
A great deal of water goes to the crops grown to feed them. This is in addition to all the water needed in the slaughter process!
Unsurprisingly, the United Nations describes animal agriculture as having ‘an enormous impact on water use’.
The water footprints for meat (excluding dairy and eggs) vary from between 4,325 litres per kilogram for chicken to 15,415 to beef. In comparison, the water footprint for vegetables is just 322 l/kg and for fruit, 962 l/kg.
DEFORESTATION & BIODIVERSITY LOSS
Livestock is the world's largest user of land resources, with grazing land and cropland dedicated to the production of feed representing almost 80% of all agricultural land. Feed crops are grown in one-third of total cropland, while the total land area occupied by pasture is equivalent to 26% of the ice-free terrestrial surface. (United Nations FAO, Animal Production)
Animal agriculture requires a huge amount of land to graze and rear animals and to produce the grain to feed them. (As noted in the UN quote above, a full third of the crops grown worldwide are used as animal feed.) The earth’s rainforests and other precious natural areas are being destroyed to provide this space. And without the trees to absorb the greenhouse gases, CO2 and other harmful pollutants are being released into our atmosphere.
For example, more than three-quarters of the Amazon rainforest has been cleared, either for use as pasture or in order to grow feed, largely for farmed animals. This is a global industry; while most of the meat is consumed domestically, the crops are shipped all over the world. You may have heard that soya is a major crop, and this is true--but only about 6% of soya is eaten by humans, while 75 to 90% is fed to farmed animals. (The remainder is used for biodiesel.)
In fact, Greenpeace found in 2020 that the UK's annual demand for imported soya for animal feed requires 1.4 hectares of land--a space the size of Northern Ireland. Of that animal feed, the vast majority of it goes to the poultry sector--both eggs and chickens who are sold at all the major supermarkets and fast food chains. Eggs have a large footprint as well The destruction of the Amazon rainforest is not just bad news for biodiversity; it is a major threat to the health and survival of Brazil's Indigenous population.
'Most people would be incredulous when they think they’re buying a piece of chicken in Tesco’s which has been fed on a crop responsible for one of the largest wholesale tropical forest destructions in recent times. (Chris Packham, Revealed: UK supermarket and fast food chicken linked to deforestation in Brazil)
But it isn't just the Amazon that's being destroyed--most of the UK's formerly forested areas have been decimated for animal agriculture over the centuries too. For example, the sheep industry requires four million hectares of land--or a full sixth of the UK's 24 million hectares--but provides just 1% of our calories. A rewilding of these areas to their former glory would be of enormous benefit not only to animals but to the planet as a whole, providing necessary carbon sinks in the form of rainforests, wetlands and savannahs.
The UK's appetite for animal products has been linked to the extinction of 33 species, with the World Wildlife Fund stating that 'Producing crops to feed our livestock is putting an enormous strain on our natural resources and is a driving force behind wide-scale biodiversity loss.'
There are 10,000 species of birds, but farmed chickens and other poultry constitute 70% of the bird life on the planet. We raise and slaughter 65 billion chickens annually, and the impact is so significant that scientists have proposed that we mark the Anthropocene--the era in which we now live--with by the landfills full of their bones. Meanwhile, livestock like cows and pigs make up 60% of all mammals. (Humans are another 36%, meaning that just 4% of mammals are wild.)
'Now we can say, only slightly fancifully: You eat a steak, you kill a lemur in Madagascar. You eat a chicken, you kill an Amazonian parrot.'
Gidon Eshel, referring to one of many studies demonstrating how species-rich habitat is being destroyed for pasture and feed crops
Animal agriculture doesn't just use an outsized amount of water: as the chart below shows, it pollutes far more than its fair share, too. Eutrophication, or the pollution of water bodies with the runoff of excess nutrients, is a major environmental issue in the UK and worldwide--and animal products are big contributers. There are multiple reasons for this but the massive amounts of waste 70 billion land animals produce annually is the biggest cause.
The use and storage of such large concentrations of waste is a significant environmental issue, with leakages from cesspools and manure spray fields a frequent occurrence. For example, as the nitrogen and phosphorous waste that comes from animal faeces contaminates our water supplies, it creates what are known as ‘dead zones’ – places where oxygen supplies are so low that aquatic species cannot survive. 415 marine areas have been identified as “dead zones” as of 2013--up from 44 areas in 1995. We aren't doing enough to combat it, and even when farms outright break the law, they generally go unprosecuted.
For example, the collapse of sea trout populations in Wales matches the distribution of dairy farms almost exactly, with an agricultural inspector admitting that fewer than 1% of the farms in Wales meet slurry containment regulations. An investigation by the Environmental Agency found that 95% of farmers in the catchment of the River Axe in south-west England do not have proper slurry containment either, with 49% of them polluting the river. And the massive, industrial free range chicken farms by the once famously picturesque River Wye have turned the water 'putrid green' and as murky as pea soup. (Learn more about the realities of 'free range' farming here.)
Besides the nitrogen and phosphorus mentioned above, other types of water pollution include pesticides, sediment, organic substances like plant matter and animal waste, pathogens like E.Coli, and metals like selenium, as well as drug residues, hormones and feed additives. The growing threat of antibiotic resistance is also significant; animals on farms are given antibiotics by default to increase their rate of growth and combat the filthy, crowded conditions in which they live, and these antibiotics end up in our water supply.
A vegan diet is more energy efficient and produces fewer greenhouse gas emissions than a diet which includes animal products.
Greenhouse gas emissions
Estimates for the total percentage of greenhouse gas emissions caused by animal agriculture vary as various studies omit certain relevant data, focusing solely on-farm emissions, for example, while excluding land use or the crop supply chain. Under these criteria, even the most conservative estimates see animal agriculture as being responsible for fully 14.5% of our greenhouse emissions. A study carried out by environmental specialists Robert Goodland and Jeff Anhang, however, suggests that meat, egg and dairy production actually accounts for 51% of annual worldwide greenhouse gas emissions. Their report includes all the aforementioned data as well as the CO2 emissions not only from animal respiration but the carbon-intensive medical treatments used to treat millions of cases of zoonotic illnesses like swine flu, avian flu and of course, COVID-19.
Why is this?
Emissions are generated through every aspect of the industry. It begins with clearing land for pasture and grazing, as well as for growing all the crops to feed animals. Energy is also used in keeping them alive, slaughtering them, and the transportation involved in these processes. (As mentioned previously on this page, however, transportation is a tiny percentage of that whole--anywhere from less than 1% to 10%--meaning that 'eating local' is not as effective as we like to think.)
Farmed animals also release methane, which has a warming effect 86 times more potent than carbon dioxide over a 20 year timeframe. Animals, especially cows, produce such large amounts through their digestive process and manure that animal agriculture is a leading cause of methane worldwide, if not the leading cause! (Is eating smaller animals like chickens the solution? Nope.)
In addition to CO2 and methane, animal agriculture is also responsible for nitrous oxide emissions. Nitrous oxide is released as the animals’ waste breaks down, either in manure lagoons or as it is spread onto fields as fertiliser. The initial production of the animals’ feed, which involves large amounts of (non-manure) nitrogen-based fertiliser, is an even bigger contributer. In terms of its potential to intensify global warming, nitrous oxide is approximately 265 times more potent than carbon dioxide.
Petter, Olivia, Veganism is 'single biggest way' to reduce our environmental impact, study finds, The Independent, 24 September 2020
Carrington, Damian, Organic meat production just as bad for climate, study finds, The Guardian, 23 December 2020
Water footprint of crop and animal products: a comparison, WaterFootprint.org
Animal Production, Food and Agriculture Organization of the United Nations
Harvey, Fiona and Dom Phillips, A fifth of Brazilian soy in Europe is result of deforestation, The Guardian, 16 July 2020
Dalton, Jane, Chicken from UK supermarkets and fast-food chains ‘fuelling mass forest loss in South America’, The Independent, 21 January 2020
Monbiot, George, Goodbye – and good riddance – to livestock farming, The Guardian, 4 October 2017
Monbiot, George, Let’s make Britain wild again and find ourselves in nature, The Guardian, 16 July 2015
Appetite for Destruction: Full Report, World Wildlife Fund, October 2017
Carrington, Damian, Humans just 0.01% of all life but have destroyed 83% of wild mammals – study, The Guardian, 21 May 2018
Corman, James, It Could Be the Age of the Chicken, Geologically, The New York Times, 11 December, 2018
Carrington, Damian, Humans just 0.01% of all life but have destroyed 83% of wild mammals – study, The Guardian, 21 May 2018
Monbiot, George, The government is looking the other way while Britain's rivers die before our eyes, The Guardian, 12 August 2020
Van der Zee, Bibi, What is the true cost of eating meat?, The Guardian, 7 May 2020
Wasley, Andrew, Fiona Harvey and Madlen Davies, Serious farm pollution breaches rise in UK – and many go unprosecuted, The Guardian, 21 August 2017
Axe Falls on Dairy Sector, Fly Fishing & Fly Tying Magazine, February 2020
Hughes, Janet, Millions of chickens in Wales are turning the River Wye green in Gloucestershire say conservationists, Gloucestershire Live, 25 June 2020
Lyons, Gwynne, Pharmaceuticals in the Environment: A Growing Threat to Our Tap Water and Wildlife, CHEM Trust, December 2014
Goodland, Robert and Jeff Anhang, Livestock and Climate Change, World Watch, November/December 2009
Methane: The other important greenhouse gas, Environmental Defense Fund
Woolley, Jamie, Is eating chicken really better for the environment than eating beef?, Greenpeace, 20 December 2019