How much water do meat and dairy use?

The objection

“Those 15,000-litre beef figures are propaganda. Most of that water is rain that would have fallen on the field anyway.”

The answer

Most of the water counted in the footprints of animal products is indeed rain, so the critic has read the accounting correctly. The stricter test is the water farms draw from rivers and aquifers, where the volumes are far smaller: 1,451 litres for a kilogram of beef from beef herds, as a global average (2018) [5]. Some plant foods are thirsty on that measure too, and studies of modelled diets are mixed [7], but a study of what 55,504 people in the UK actually ate (2023) still found heavy meat-eaters’ diets drawing 2.2 times as much farm water as vegans’ [1].

Is most of the water behind meat just rain?

Most of it is: Hoekstra (2012) put the global water footprint of animal production at 2,422 billion cubic metres a year, and 87% of that was green water, the rain stored in soil that pasture and crops take up [2]. Blue water, taken from rivers, lakes and groundwater, made up 6%, and grey water, the volume needed to dilute the pollution farming releases, 7% [2]. Counting all three, rain included, Mekonnen and Hoekstra (2012) found that any animal product had a larger water footprint than crops of equivalent nutritional value, largely because of how much feed an animal needs for the food it yields [3]. The size of that gap varies widely: per calorie, beef’s footprint averaged 20 times that of cereals and starchy roots, while per gram of protein, milk, eggs and chicken took 1.5 times as much as pulses [3]. Animals from industrial systems generally consumed and polluted more ground and surface water than those from grazing or mixed systems, which is one point in grazing’s favour, though the authors still concluded that from a freshwater perspective crops are the more water-efficient source of calories, protein and fat [3].

Do meat and dairy use more river and groundwater than plant foods?

Meat and dairy mostly use more river and groundwater than the plant foods that would replace them, though not every plant food is frugal. In Poore and Nemecek’s data from 38,700 farms (2018) [4], charted by Our World in Data as global averages, a kilogram of cheese takes 5,605 litres of freshwater withdrawals against 149 for tofu, cow’s milk 628 litres against 28 for soy milk, and beef from beef herds 1,451 litres against 397 for peas, while beef from dairy herds takes 2,714 [5]. Nuts, at 4,134 litres a kilogram, rice, at 2,248, and groundnuts (peanuts), at 1,852, all use more than beef from beef herds [5], so how much river water a switch saves depends on what takes the meat’s place. Averages hide a wide spread: Poore and Nemecek found that the same product’s impacts can vary 50-fold between producers, though even the lowest-impact animal products typically exceeded their plant substitutes [4].

How much less water does a vegan diet use?

Among 55,504 people in the UK, vegans’ diets used a little under half the farm water of heavy meat-eaters’ diets (2023) [1]. Scarborough and colleagues at Oxford matched what these vegans, vegetarians, fish-eaters and meat-eaters recorded eating to Poore and Nemecek’s database of 570 life-cycle assessments covering more than 38,000 farms in 119 countries, and found that vegans’ diets used 46.4% of the water of diets with 100g or more of meat a day [1]. The water figures are therefore global farm data applied to what the UK volunteers ate, not measurements of British farms; for each food the authors drew 1,000 values from the spread of farms in the database, so the results carry the wide variation in where and how food is produced [1]. Scaled to 2,000kcal, the median vegan diet used 410 litres a day, vegetarians 530, fish-eaters and low meat-eaters 710, medium meat-eaters 780 and high meat-eaters 890 [1]. Water was among the study’s least certain measures. The vegan figure’s 95% uncertainty interval ran from 21.0% to 81.0% of high meat-eaters’ use, and a simpler analysis in the same paper, using each food’s median value, put high meat-eaters at 1.7 times vegans’ water use against 2.2 in the main analysis [1]. The authors prefer the fuller analysis because using medians ignores how widely each food’s footprint varies, which they showed can shrink the differences between diets [1]. On emissions and land the gap was wider, with vegan diets at about a quarter of high meat-eaters’ [1]. The diets were recorded between 1993 and 1999 from volunteers recruited partly through vegetarian magazines and societies, so they are not a random sample of the country [1].

Pooled evidence from modelled diets points the same way on average, but less consistently. Aleksandrowicz and colleagues’ systematic review (2016) found 34 scenarios that estimated the change in water use when a population’s average diet was swapped for a more sustainable one: the median change was a cut of 18%, vegetarian scenarios cut most (median 37%), and the only vegan scenario raised water use by 107% [7]. The review traced increases like that to studies in which nuts, fruit and vegetables used more water per calorie than several animal foods [7]. Each of those scenarios was a diet drawn up by modellers, and the Oxford authors point out that modelled diets often fail to reflect how people really eat [1]. That is why this page leans on their study, in which every one of the 55,504 diets was recorded by the person who ate it and all were scored against the same water figures [1].

How much of the world’s fresh water goes on farming?

Agriculture took 71% of the fresh water withdrawn worldwide in 2022, counting irrigation and livestock, in FAO’s AQUASTAT figures as published by the World Bank [6]. Mekonnen and Hoekstra (2012) found that nearly a third of agriculture’s total water footprint, rain included, comes from producing animal products [3]. Water quality suffers too. Eutrophication is the dense growth of algae and plants fed by excess nitrogen and phosphorus in water, and in the Oxford study (2023), vegans’ diets had 27.0% of the eutrophication potential of high meat-eaters’ diets [1].