Extinction

Farm animals have taken the place of wild animals

By WhyStopHarmingAnimals.com

Weigh every mammal on Earth that isn’t human, and about 94% of that weight is cows, pigs and other farm animals[1][2]. Wild mammals, from whales and elephants to mice and bats, make up the other 6%[1]. Farm animals outweigh them about 15 to 1[1][2], and on land alone the farm-animal share is 97%[1]. Meanwhile around a million species of animals and plants face extinction[5][6], and the land taken to raise and feed farm animals is one of the main reasons.

The weight of life on Earth

The biomass figures come from Our World in Data’s reading of a 2018 census of life on Earth by Bar-On, Phillips and Milo, published in PNAS[1][2]. The authors measured life in tonnes of carbon so that very different organisms could be compared. By their estimate, farm animals account for about 0.1 gigatonnes of carbon and wild mammals for about 0.007[2]. Including humans, people and their farm animals make up about 95% of all mammal biomass, and wild mammals about 5%[3].

Birds follow the same pattern. Chickens and other poultry weigh about 0.005 gigatonnes of carbon, against about 0.002 for all wild birds combined[2], so farmed birds outweigh wild ones[3] about two and a half to one[2] and make up about 71% of the weight of every bird on Earth[1][2]. Faunalytics, working from FAO data, counts about 78.5 billion chickens killed for food in 2024 alone[4].

Bar-On and colleagues also looked back in time[2]. Using an earlier estimate by Barnosky, they found that wild land mammals now weigh about seven times less than they did before humans spread across the planet[2], and sea mammals fell about fivefold after industrial hunting. Yet total mammal weight went up, because the wild animals were replaced by animals bred to be eaten.

A million species at risk

The 2019 global assessment by IPBES, the intergovernmental science panel on biodiversity, found that around a million animal and plant species face extinction, many within decades[5], and named agriculture among the largest threats[5]. More than a third of the world’s land surface and nearly 75% of its freshwater resources are devoted to crop or farm-animal production[5]. Nature’s news coverage of the assessment put it the same way: up to a million species at risk[6], and agriculture one of the biggest threats to the planet’s ecosystems[6].

The UN Environment Programme calls the global food system the primary driver of biodiversity loss[7]. In its accounting, agriculture is an identified threat for more than 85% of the 28,000 species at risk of extinction[7].

Why farm animals are at the center

Those assessments count agriculture as a whole, including the crops people eat[5][7]. Other figures show how much of it belongs to farm animals. About 80% of agricultural land is used for grazing and feed[8], while meat and dairy supply about 18% of the world’s calories. The Oxford Martin School found that cow farming alone accounts for 41% of the global biodiversity damage linked to farmland[10].

The chain is direct. Wild species need habitat. Habitat is cleared to make pasture and to grow soy and corn for feed, and the cleared land is filled with cows, pigs and chickens bred in their billions to be killed. A global shift to plant-based diets would cut agricultural land by about 75%[11], from about 4.1 billion hectares to about 1 billion, and most of what came back would be pasture and feed cropland, the land wild species have lost.

What the numbers show and what they don’t

The sevenfold decline in wild land mammals did not all come from farming. Much of it happened long ago, when people hunted the largest animals out of existence, and the pre-human baseline comes from an older reconstruction. The biomass figures are global estimates built from many data sources. IPBES and UNEP do not split farm animals out from other farming[5][7], so they cannot say how many of those million species are at risk because of meat, dairy and eggs in particular.

The land figures and the Oxford Martin analysis close most of that gap[10]. Raising animals is the largest single use of farmland on Earth[8], and the mammals and birds alive today are mostly animals kept by people to be killed[1][2], while the wild ones survive in the space left over. None of those farm animals has to be bred for anyone to be well fed, and each of them is someone, not a quantity of carbon.