Environmentalists often say that humanity needs to shrink its planetary footprint. Now, a new study has demonstrated how literally massive that footprint is.
While the mass of Earth’s life forms stands at about 1.1 trillion metric tons (1.2 trillion U.S. tons) and has not changed much in recent years, the so-called “anthropogenic mass” of artificial materials is growing exponentially. The mass of everything people have built and made, from concrete pavements and glass-and-metal skyscrapers to plastic bottles, clothes, and computers, is now roughly equal to the mass of living things on Earth and could surpass that this year, according to research published today in Nature.
The finding may bolster the argument that Earth has entered the Anthropocene, a proposed geologic epoch in which humans are the dominant force shaping the planet. As senior study author Ron Milo of the Weizmann Institute of Science in Rehovot, Israel puts it, the world is undergoing a material transition that “happens not just once in a lifetime, but once in an era.”
While that insight is more symbolic than scientifically meaningful, the material scale of the human enterprisehelps explain how we’ve managed to transform global nutrient cycles, alter the climate, and drive myriad species to the brink of extinction.
This isn’t the first attempt to weigh humanity’s impact on the planet. In 2016, a team of scientists estimated the weight of the “technosphere”—including not just wholly artificial buildings and products, but also the approximate weight of the land and seafloor that we’ve excavated, modified...