Limits to sustainable animal consumption
Farming
- Vegans rightly point out that meat-containing diets require more land (and thus more deforestation). Feeding animals crops 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" 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?
Analysis in progress - someone is working on this research.
Results will be posted here soon ♥
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: (calculation loading) Grams of protein: (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.