Why Wild Mammal Biomass Has Declined

Super fact 70 : Wild mammals have declined by 85% since the rise of humans even as the total mammal biomass has nearly tripled. The result is that only 4-5% of the total biomass of mammals are wild animals. The rest are humans and livestock.

Pie chart shows that Livestock, mostly cattle and pigs, corresponds to 60% of the mammal biomass, humans are 36%, and wild mammals are 4%. | The Wild Mammal Biomass Has Substantially Declined — Livestock, mostly cattle and pigs, corresponds to 60% of the mammal biomass, humans are 36%, and wild mammals are 4%. The data is taken from this article.

As stated, mammal biomass has declined by 85% since the rise of humans. This is despite a threefold increase in mammal biomass over the last 200 years. However, this increase is almost entirely due to the growth of human and livestock populations. The result is that only 4-5% of the total biomass of mammals are wild animals. Another result is that Earth’s wild land mammals now make up just 2% of the mammal kingdom. You can read more here, or here, or here, and more in depth here.

Humans are 36% of the mammal biomass, Sheep is 4%, Livestock and pets 59%, including 2% dogs, 3% pigs, goats 3%, cattle 38%, and buffalo 6% — Humans and our livestock dominate global mammal biomass. Biomass is the total weight of each animal group. It’s calculated by multiplying an estimate of the total number of individuals by their average mass. Shown is each group’s share of global mammal biomass. This graph is taken from Our World In Data.

I think this is a super fact because we know it is true, and this huge and extremely rapid change of Earth’s fauna (from a geological timescale) is certainly important, and yet I think it comes as a surprise to many people. I often see the argument that humans have been great for animals because there are many more of them and the mammal biomass has tripled. That argument leaves out the part about the increase in mammal biomass coming from domesticated animals while wild animals have been disappearing. One question that comes to mind is whether life at the cramped factory farm is better than the life as a wild animal.

Wild Mammal Biomass Data

Below are a couple of graphs displaying some additional information on wild mammal biomass.

The graph shows that even hoofed mammals is a big group consisting of 49% of the wild mammal biomass. Rodents are 16% and elephants are 8%, bats are 7%, Marsupials are 7%, and primates are 4%, carnivores 3%, rabbits 1%, and other mammals 4%. — The distribution of the world’s wild land mammal biomass. The graph is taken from Our World in Data.

Another thing to note is that the wild animal biomass is very concentrated to just a few species. Considering that there are between 6,500 and 6,800 recognized mammal species in the world, it is quite remarkable that only 10 species make up 40% of the mammal biomass.

White-tailed deer is 12%, Wild boar is 8%, African Savanna Elephant is 6%, Eastern gray kangaroo is 2%, Mule deer is 2%, Moose is 2%, Red Deer is 2%, European roe deer is 1.8%, Red Kangaroo is 1.8%, and the Common Warthog is 1.4%.| The Wild Mammal Biomass Has Substantially Declined — Just 10 species make up around 40% of wild mammal biomass on land. The graph is taken from Our World in Data.

Reasons for Decline of Wild Animal Biomass

This decline of wild mammal biomass is primarily caused by human activity, including hunting, habitat loss and degradation from agriculture and urbanization, climate change, and pollution. This human-driven extinction event is the result of a rapidly growing human population and its increased consumption of natural resources, leading to widespread disruption of ecosystems and dramatic declines in wild mammal populations. It should be mentioned that the extinction of large mammals such as mammoths, American mastodon, giant ground sloths and glyptodonts was likely aided by human hunting in prehistoric times. The largest mammals have always been at the greatest risk for extinction and that is still true today.