According to the latest available calculations, the human population is about 7.5 billion individuals. We will have to wait until 2025 to cross the 8 billion barrier, and that fact forces us to once again evaluate the impact we are having on Earth as a species. An interesting starting point for this is to measure our equivalent in biomass, or rather, the total weight of humans in tonnes of carbon, and the results are striking: We are not special, but the damage we do is enormous.
The study, conducted by Yinon M. Bar-On, Ron Milo (both from the Weizmann Institute of Sciences) and Rob Phillips (Caltech), begins by stating that the total biomass on the planet amounts to 550 gigatonnes of carbon, or 550,000 million metric tonnes. 450 of those gigatonnes (almost 82 percent) are nothing more than plants, thus confirming the absolute dominance of the plant kingdom. The second place belongs to bacteria, with 70 gigatonnes of carbon (about 13 percent). The rest of everything alive in the world manifests itself in that final 5 percent, and we appear there... occupying a tiny fraction.
The Weight of Humans on Earth
The exact number? 0.06 gigatonnes of carbon, something like 0.01 percent of global biomass, or 36 percent of all mammals. Only 4 percent of that category represents wild animals, while the other 60 percent of mammalian biomass is livestock (cattle). And there's more: If we take all the birds on Earth, 70 percent of their biomass is made up of poultry. According to the words of Dr. Milo himself, when assembling a puzzle with his daughters he usually sees an elephant, a rhinoceros and a giraffe together, when the most scientifically realistic scene would be three cows together, accompanied by a chicken.
That explosion of domestic animals definitely helped increase total mammalian biomass, however, the losses have been very significant. Always speaking in biomass parameters, since the birth of human civilization, 83 percent of wild mammals, 80 percent of marine mammals, 50 percent of plants, and 15 percent of fish have disappeared.
