The need for extracted water for animal agriculture varies based on factors like feed irrigation, particularly in water-restricted regions. Yet, shifting to plant-based diets is not universally water-saving due to context. Claims about extreme water usage for livestock, such as 15,500 litres per kilogram of beef, overlook that this water largely comes from rainfall and is part of the natural water cycle (which would occur regardless of livestock presence). The water footprints of grass-fed animals are to be seen as more indicative of local climate patterns than of actual water wastage. Vegan diets might even increase extractive water needs, particularly for water-intensive plant products. Expressing water needs per unit of nutrition rather than per kilogram of food further contributes to a fairer comparison across different food categories. Ultra-processed foods exacerbate water footprints. In sum, water usage in animal agriculture and plant-based foods is complex and context-dependent. Rainfall plays a significant role, and comparisons should factor in nutritional value and local conditions.
This subsection contains the following topics:
- Situating the problem
- Argument 1: most water in animal agriculture comes from rainfall
- Argument 2: the need for extracted water is situational
- Argument 3: wastage per unit of food can often be higher for crops
_________________________________
Situating the problem
Animal agriculture accounts for 8-10% of global freshwater usage and one-third of all agricultural freshwater use. Approximately 37% of water employed in crop production serves as feed for animals. However, data regarding water usage is often presented without proper context. Claims that beef requires more water per calorie than other livestock products have led to the assertion that over 15,000 litres are needed to produce a kilogram of beef. Yet, this perspective fails to acknowledge several important factors, for reasons outlined in the three arguments below. However, it remains important to emphasize that these arguments do not dismiss the concerns valid in livestock systems heavily reliant on extractive water resources, especially in situations where water scarcity is a significant issue.
Further reading (summary of the literature):
Animal agriculture requires 8-10% of global fresh water and 1/3 of the fresh water used in agriculture [Nordhagen et al. 2020]. About 37% of the water used in crop production is used for feed [Herrero et al. 2013]. Often, however, data is presented out of context. Beef is said to need more water per calorie than foods from other livestock categories [Eshel et al. 2014], leading to the widespread claim that >15,000 liters are needed to produce a kg of beef.This overlooks, however, that (1) 'water' is a complex and differentiated category, (2) that results differ vastly between different regions, climates, and management practices (e.g., irrigated feed production versus grazing), and (3) that ASFs are not necessarily more wasteful than crops, especially when accounting for nutritional value. To be clear, these arguments indicate the need for contextualization but do not preclude that concern is warranted in systems that rely heavily on extractive water, especially for feed production and in areas where water scarcity is problematic.
Argument 1
Most water in animal agriculture comes from rainfall
Life cycle assessment methodologies attribute nearly 90% of water used in animal husbandry to rainfall ('green' water), which is a natural part of the water cycle irrespective of livestock presence. For grazing ruminants, this percentage is even higher, at 94%. The water footprints of grass-fed ruminants primarily reflect local rainfall patterns, rather than indicating wasteful water use. This is especially evident in areas with high rainfall, such as marginal lands or mountainous regions unsuitable for plant agriculture. While local climate, geography, and context play crucial roles (including the potential need for irrigation with 'blue water', it is incorrect to label animal husbandry as inherently wasteful regarding water resources.
Further reading (summary of the scientific literature):
Overall, life cycle assessment (LCA) methodologies ascribe almost 90% of the water used in animal husbandry to rainfall ('green' water), which would fall anyway and enter the natural water cycle regardless of the presence of livestock. For grazing ruminants, this percentage is higher still (94%) [Mekonnen & Hoekstra 2010].Rather than being a reflection of water wastage, water footprints of grass-fed ruminants mostly reflect how rainy the local climate is. To further underline that point, footprints are particularly high in marginal lands with high rainfall that are otherwise not suitable for plant agriculture (e.g., in mountainous areas). Obviously, much will depend on local climates, geography, and overall context (e.g., need for irrigation with 'blue water') but it is misleading to state that animal husbandry is inherently wasteful as far as water resources are concerned.Explanatory video 💬 del Prado 2023
Argument 2
The need for extracted water is situational
The primary concern regarding water wastage is the utilization of water for crop irrigation, particularly in water-scarce regions. Pressure on freshwater systems is minimized when relying on crop residues, waste, and roughages for agricultural purposes. Beef produced through pasture-based systems demands significantly less water (some 250-1,000 litres per kg), due to reduced reliance on grain-based feed. The variability in water wastage varies thus considerably based on different production practices and local specificities. In the US, for instance, water requirements for beef production range from 100 to 15,000 litres per kg of carcass weight, averaging around 2,000 litres/kg at the farm-to-gate stage. In some Australian systems, 5-500 litres of water suffice to produce one kilogram of meat, which is comparable to cereal cropping.
Further reading (summary of the literature):
Pressure on freshwater systems is generally at its lowest when dominantly based on crop residues, waste, and roughages [Paul et al.2021]. The main concern with respect to water wastage is thus the use of water for crop irrigation, especially in water-restricted regions. In the US, 90% of blue water withdrawals for agriculture is used for irrigation, of which 60% is destined for feed crop production, i.e., corn (25%), forage (18%) and soybeans (14%) [Kleppel 2020, citing USDA/ERS].Blue water needs for US beef vary from 100 to 15,000 liters per kg of carcass weight (farm-to-gate), averaging 2,000 liters/kg carcass weight, but depending on the region and crop irrigation needs [Rotz et al. 2019]. Pastured operations require 50–90% less water due to the lower dependence on grain-based feed, resulting in 250-1,000 liters/kg (mostly to produce forage and hay-based products) [Kleppel 2020]. In Australia, LCAs of selected lamb and beef production systems have shown that only 5-500 liters of water are needed to produce one kg of meat [Peters et al. 2010; Ridoutt et al. 2012a,b].
Argument 3
Wastage per food unit can often be higher for crops
Shifting to plant-based diets might not consistently lead to water wastage reduction, as outcomes vary by context. Vegan food scenarios and climate impact reduction efforts might even increase water scarcity footprints. In many cases, animal source foods need comparable or even less irrigation water than major plant crops. Some plant foods lead to particularly high water wastage, as is the case for nuts and fruits imported from water-stressed countries. Moreover, comparing water needs per unit of nutrition rather than per kg of food provides a more equitable comparison across diverse food categories. Protein quality considerations, for instance, influence water usage rankings, with wheat, rice, and maize becoming higher water consumers. Ultra-processed foods further exacerbate water footprints, potentially accounting for a significant portion of dietary-related water usage in high-income countries.
Further reading (summary of the literature):
The above-mentioned data for Australian lamb and beef (5-500 l/kg) are not all that different from the ones obtained for cereal cropping in the same region (1-150 l/kg at farm gate) [Ridoutt et al. 2012]. Another study indicated that non-beef livestock products (dairy, pork, poultry, eggs) had on average less requirements for irrigation water per caloric unit than some of the major plant crops (potatoes, rice), without even taking into account nutritional value [Eshel et al. 2014].Various plant foods can be very water intensive, as is the case for the 'blue' water requirements of asparagus (>700 l/kg) and beans (>200 l/kg) for the UK market [Frankowska et al. 2019a]. Fruits that are largely imported from water-stressed countries with high irrigation requirements, such as avocados (>1,000 l/kg), mangoes (>900 l/kg), and plums (>500 l/kg), are particularly water demanding [Frankowska et al. 2019b]. Californian almonds even require >10,000 l/kg [Fulton et al. 2019]. In a study of the Swedish diet, nuts were the most demanding for freshwater use of all investigated foods, at some 2,000 l/kg, while cocoa and rice also had higher requirements than meat and cheese [Moberg et al. 2020]. The same study also showed that plant-derived foods contributed to >30% of freshwater use in the Swedish diet, particularly due to the consumption of foods imported from regions where high irrigation levels are needed (nuts, rice, oil, coffee, and fruits).A shift to plant-based diets or adherence to dietary guidelines would therefore not necessarily be beneficial in view of water wastage reductions, as this will strongly depend on the context. In Australia, for instance, gains in climate impact reduction are expected to come at the expense of increased water-scarcity footprints [Ridoutt et al. 2021]. In the UK, the share of tropical fruits has rapidly increased between 1987 and 2013, paralleling an overall increase of the proportion of fruit and vegetables from climate-vulnerable and water-poor countries from 20% to 32% [Scheelbeek et al. 2020]. Meanwhile, the proportion of domestically grown fruit and vegetables dropped from 42% to 22%, which may compromise future food security [Scheelbeek et al. 2020]. Also, rice wastage in Asia and fruit wastage in Asia, Latin America, and Europe constitute extractive ('blue') water hotspots [FAO 2013].Finally, expressing the water need per unit of nutrition rather than per kg of 'food' would more fairly compare between vastly different food categories (e.g., beef offers more essential nutrition than cereals). When taking into account protein quality, wheat, rice and maize shift from the lowest to the highest categories of water use, whereby pork production becomes more efficient than wheat on a digestible lysine basis [Moughan 2021]. Accounting for priority micronutrients (vitamins A, B9, and B12, calcium, iron, zinc) also leads to shifts in comparison between ASFs and plant foods, with nuts, rice, and various fruits now having the highest impact on fresh water withdrawal [Katz-Rosene et al. 2023]. Based on German data, a vegan food basket scenario would double the need for extractive water, especially for water-intensive plant products such as nuts and seeds [Meier & Christen 2013]. Shifts to ultra-processed foods, driving overconsumption, may further aggravate water footprints [da Silva et al. 2021]. The latter foods may even be responsible for up to a quarter of the dietary-related water usage among adults in high-income countries [Anastasiou et al. 2022]. In the Swedish diet, for instance, "sweets, snacks and drinks" caused 24% of the overall impact.
