Limits to sustainable animal consumption
Tl;dr: The limit is about 17 g protein/day per person - in total, dairy and meat, from all grass-fed animals and wild-caught fish.
Farming
- Vegans rightly point out that meat-containing diets require more land (and thus more deforestation). Feeding crops to animals is a net loss of protein and calories. But...
- Pro-meat folks rightly point out that some land is only suited for grazing animals. And unlike humans, cows can live on eating grass
(...)( and so can buffalo, sheep and goats. But chickens & pigs can't. ) .
This raises a more important question:
- If farm animals only ever ate...
- grasses and other plants from pasture & range
(...)( especially from biodiverse natural lands that keep a lot of carbon stored in the roots of plants ) , and - the parts of food crops that humans can't eat
(...)( for example corn cobs after the kernels have been removed (ruminants can digest certain kinds of fibrous matter that other species can't) ) ,
- grasses and other plants from pasture & range
- and never...
- human-edible food crops
(...)( including corn and soy as those could be made into flour ) (...)( Grey area: Perhaps also include "spent grains" and "fryer waste oil" here, because the original materials were human-edible, and the downgrading was a choice. ) , nor - crops grown specifically for animal feed
(...)( Grey area: Perhaps also include the more superficial types of "pasture" that are monoculture-like and don't keep a lot of permanent roots. The exact definition can be specified in the answer to the question. ) ,
- human-edible food crops
- how much animal protein
(...)( from meat, milk and/or eggs etc ) could be produced?
Clearly it's less than the status quo, as there are fewer sources of feed. But how much less?
Estimate
About 12 grams of animal protein per day, per capita, globally.
This includes both meat and dairy, from all animals (ruminants).
Breewood, H. & Garnett, T. (2020). What is feed-food competition? (Foodsource: building blocks). Food Climate Research Network, University of Oxford.
Page 10
References primary source:
Mottet, A., de Haan, C., Falcucci, A., Tempio, G., Opio, C., & Gerber, P. (2017). Livestock: On our plates or eating at our table? A new analysis of the feed/food debate. Global Food Security.
Soybean meal is not counted here, because it can be turned into human food (soy flour).
Source:
Breewood, H. & Garnett, T. (2020). What is feed-food competition? (Foodsource: building blocks). Food Climate Research Network, University of Oxford.
Page 10
References primary source:
Mottet, A., de Haan, C., Falcucci, A., Tempio, G., Opio, C., & Gerber, P. (2017). Livestock: On our plates or eating at our table? A new analysis of the feed/food debate. Global Food Security.
Source:
Mottet, A., de Haan, C., Falcucci, A., Tempio, G., Opio, C., & Gerber, P. (2017). Livestock: On our plates or eating at our table? A new analysis of the feed/food debate. Global Food Security.
The number is mentioned in the Abstract: https://www.tabledebates.org/research-library/livestock-our-plates-or-eating-our-table
^ Total amount of protein from both meat and dairy, combined. (calculation loading)[''']This is probably a slight overestimate, because feed efficiency ratios tend to be lower when cows are fed less grain.
This is less than the status quo, because the animals wouldn't be fed corn grain or soybean meal
Status quo
Ruminants (cows, buffalo, goats and sheep) produce a total of about 16 g/day of protein per capita globally.
- 10 g/day protein from milk
(...)( from 297 mL/day of milk ) per capita - 6 g/day protein from meat
(...)( from 30 g/day of meat ) per capita - This was calculated in Code:food2.sql.
Not all of this is grass-fed. Also, grass-fed animal production can't really increase without destroying forests and other wildlife, because most of the world's farmland is already pasture, and that's not even counting rangelands which are also already grazed upon.
Total animal protein production (all animals) is about 35 g/day per capita globally. Consumption is less, because some of it goes to waste.[QUANTIFICATION needed]
Hunting
Hunter-gatherer lifestyles were sustainable in prehistoric times when the world population was less than 0.1 billion - today we are at 8.0 billion. Hunting might be a great survival tactic if you're lost in the woods. But it's not going to feed the world. There would be mass extinctions of wild animals if we tried.
Fishing
Wild-caught fish could provide 5 or 6 grams/day of protein per capita globally, if none of it was wasted.
Using most recent data available.
Fishing grew a lot from 1960 to 1990 but (unlike fish farming) has not increased since 1995. This suggests that we've reached the ecological limit.
https://ourworldindata.org/fish-and-overfishing
Last updated in 2023
Grams of fish: Grams of protein: (calculation loading) (calculation loading)
The sustainable level of consumption might be a bit less than this, because overfishing is still an issue.
The rest of fish is farmed, which, as mentioned earlier, is a net loss of protein. Farmed fish are fed food crops that humans could otherwise eat.
FAQ
Backyard chickens can't solve the food-inefficiency problem, but they can at least reduce the animal cruelty problem. Backyard chickens are generally treated better
Writer's comments
This page mostly deals with the inefficiency problems in agriculture. It doesn't account for other environmental issues such as methane emissions or soil depletion, or other ethical issues like animal cruelty
See also
- Food - main topic
- Food/faq - to answer questions such as "if we ate less meat, what would happen to existing farm animals?"
- Plant-based food, which can provide the rest of dietary protein & calories.