Extinction
Wild animals were wiped out. Farm animals took their place.
6%of non-human mammal biomass is wildlife — 94% is farm animals
If you weighed every mammal that isn’t a human, about 94% of that weight is cows, pigs, and other farm animals — they outweigh wild mammals about 15 to 1. On land only, it is 97%. About 71% of the weight of all birds is chickens and other poultry, only 29% of bird biomass are wildlife. There are magnitudes less wildlife now since humans started mass breeding farm animals, when we don't need to eat them at all. Around a million more species are at risk for the same reason; farming is listed as a threat for more than 85% of species already at risk. Again, we do not have to harm or eat animals at all.
What the evidence says
The main points first. Every claim is tied to a source below.
Our World in Data · Environmental impacts of food production
Only 6% of non-human mammal biomass is wildlife — 94% is farm animals
Our World in Data, using Bar-On, Phillips, and Milo: if you weigh every mammal that isn’t a human, about 94% is cows, pigs, and other farm animals. They outweigh wild mammals about 15 to 1. On land only, it is 97%. Wild mammals were pushed out. Farm animals were put in their place. We do not have to mass-breed or eat any of them.
71% of the weight of all birds is chickens and other poultry
The same count: about 71% of the weight of all birds is farmed poultry, mostly chickens. Poultry outweighs wild birds more than 3 to 1. The sky is not full of wild birds. It is full of a farmed species we kill by the tens of billions.
A million more species are at risk — because we mass-breed animals we don’t have to eat
IPBES: around a million animal and plant species face extinction, many within decades. That is not a mystery. We cleared their land and replaced them with cows, pigs, and chickens we mass-breed to kill. UNEP lists farming as a threat for more than 85% of species already at risk. We do not have to harm or eat animals at all.
Wild land mammals weigh about seven times less than they used to
Bar-On and colleagues, using Barnosky’s older estimate: wild land mammals now weigh about seven times less than they did before humans hunted the big ones out. Sea mammals fell about fivefold after industrial hunting. Total mammal weight still went up — because we replaced the wild ones with the animals we breed to eat. We do not have to mass-breed or eat any of them.
Sources
Papers and datasets. Caveats stay on the card — small samples and single animals included on purpose.
PNAS, 2018 · Review
The biomass distribution on Earth
Bar-On, Phillips & Milo: livestock biomass (~0.1 Gt C) far exceeds wild mammals (~0.007 Gt C). Poultry (~0.005 Gt C, mostly chickens) is about threefold wild birds (~0.002 Gt C) — about 71% of bird biomass. Wild land-mammal biomass is about sevenfold lower than pre-human estimates.
Our World in Data · Review
Our World in Data — environmental impacts of food
94% of non-human mammal biomass is livestock (about 15-to-1 vs wild mammals; 97% on land only). 71% of bird biomass is poultry livestock.
Our World in Data · Review
Almost all mammal biomass is humans and farm animals
OWID’s reading of the same census: humans and livestock make up about 95% of mammal biomass; wild mammals are about 5%. Poultry outweigh wild birds.
IPBES / United Nations, 2019 · Review
IPBES — a million species at risk
Around a million animal and plant species face extinction, many within decades. Agriculture is among the largest threats. More than a third of the world’s land and nearly 75% of freshwater are devoted to crop or livestock production.
UNEP · Review
UNEP — food system is the primary driver of biodiversity loss
The global food system is the primary driver of biodiversity loss. Agriculture is an identified threat for more than 85% of the 28,000 species at risk of extinction in that accounting.
Nature, 2019 · Review
Nature — agriculture among the biggest threats
News write-up of the IPBES assessment: up to one million species face extinction, and agriculture is one of the biggest threats to Earth’s ecosystems.