The global distribution of biomass is a key property of the biosphere, but a quantitative account of global biomass for all taxa of life is lacking. Ron Milo and colleagues compiled a global biomass census based on hundreds of studies from recent decades, combining existing estimates with newly generated estimates for taxa for which previous estimates did not exist.
The census yielded a total biomass of 550 gigatons of carbon (Gt C). Approximately 450 Gt C, or 80% of the biomass, was composed of plants, and another 70 Gt C, or 15% of the biomass, was composed of bacteria. Land biomass was about two orders of magnitude greater than marine biomass. Nearly all plant biomass was on land, whereas most animal biomass was in the oceans, and most bacterial and archaeal biomass was in deep subsurface environments, such as aquifers and beneath the seafloor. In the oceans, biomass of consumers exceeded that of producers, and vice versa on land.
The total biomass of humans and livestock exceeded that of wild mammals by an order of magnitude. Comparison of the census with historical biomass estimates suggests that human activities have led to significant reductions in wild mammal, fish, and plant biomass, according to the authors.