How The Ratio of Earth's Mammals Has Changed

In 1850, the total biomass (weight) of all the earth's wild mammals was about equal to the biomass of humans and their domestic animals. As you can see from the graph above, that has changed considerably in the 175 years since. A new study published in the journal Nature Communications traces the changes in that biomass. The total weight of domesticated mammals is more than ten times the total weight of wild mammals! In the domesticated mammal category, two-thirds of that biomass is cattle. We have a lot of them, and they weigh a lot. The other third of that category includes all other livestock, such as sheep and pigs, all cats and dogs, and mice and rats who depend on humans for their survival. Horse populations have declined. You already know about the population growth of humans. 

The total biomass of wild land animals has declined, but not nearly as much as that of marine mammals. That decline is mostly the result of hunting whales. The number of whales dropped steeply during the 20th century, and has only recovered slightly since whaling bans went into effect. Read more about these changes and their causes in the published paper. -via Damn Interesting