At the start of the 20th century, everything created by humans, including buildings and roads, weighed a small fraction of what all the living things on Earth did. But the amount of human-made stuff has been doubling every 20 years while wildlife and plant biomass shrinks, and scientists believe this is the "crossover" year when artificial objects outweigh the combined weight of all the plants, animals, fungi, and other life for the first time, reports Scientific American. Concrete and aggregates including gravel make up much of the weight. Researchers, who say human-made stuff weighs around 1.1 trillion metric tons, say their estimate is a conservative one that only includes things in use, not waste.
The rate at which humans produce stuff is accelerating. "On average, for each person on the globe, anthropogenic mass equal to more than his or her bodyweight is produced every week," researchers note in a study published in the journal Nature. "The significance is symbolic in the sense that it tells us something about the major role that humanity now plays in shaping the world and the state of the Earth around us," lead researcher Ron Milo of the Weizmann Institute of Sciences in Rehovot, Israel, tells the BBC. "It is a reason for all of us to ponder our role, how much consumption we do, and how can we try to get a better balance between the living world and humanity." (Read more environment stories.)