October 2018

A recent article in PNAS (http://www.pnas.org/content/115/25/6506.long) reports on the estimated biomass of all living things, comprising about 550 gigatons of carbon (Gt C).  It is deeply satisfying to me, as a plant biologist, to see that plants make up by far the bulk of our world’s biomass. In that tiny corner devoted to animals, an even tinier portion is devoted to humans, who make up far less than 1% of earth’s biomass. Despite our miniscule representation, the impacts of human civilization on global biomass are quite profound. Since the domestication of animals, the total biomass of wild mammals decreased approximately six-fold, while the mass of humans and domesticated livestock (mainly cows and pigs) increased about four-fold. Humans have also reduced the amount of carbon sequestered by plants by roughly two-fold through logging and clearing for agriculture. These rapid and drastic changes underscore the need to better understand how human activity affects our planet and emphasizes the need to think broadly as we consider ways to improve global sustainability.