Collectively, humans have a gargantuan ecological footprint—and the evidence is all around us. Forests are razed down to build highways, cities keep growing taller and wider, roads are paved to accommodate millions of cars and plastic pollution has permeated every ecosystem on Earth.
All those human-made materials—like steel, concrete and plastic—may now outweigh all life on Earth, reports Sandra Laville for the Guardian. In a report published yesterday in Nature, a team of scientists calculated that in 2020, human-made materials reached 1.1 trillion tons, exceeding the mass of all living things on the planet, which includes people, bacteria, plants and animals combined.
Concrete, a building block of our cities and towns, accounted for the most mass, followed by steel, gravel, brick and asphalt, reports Maddie Stone for National Geographic. Plastic is also a key player in tipping the scale, reports the Guardian. The study found that plastic alone is double the weight of all animals combined. Given the type of materials, the study suggests that urban development and increased consumption are driving this trend.
"If you weren’t convinced before that humans are dominating the planet, then you should be convinced now," Timon McPhearson, an urban ecologist at the New School in New York who was not involved with the research, tells Erik Stokstad for Science.
To reach this number, a team of scientists pulled together previous estimates of biomass and supplemented it with satellite data to track how global vegetation has changed. Then, they used numbers from a study published in 2018 that estimated how much human-made material is produced in a year, reports Science.
Their calculations reveal that in the early 1900s, human-made materials weighed around 35 billion tons—about 3 percent of the Earth's biomass. But at this point, humans are producing 30 billion tons of materials each year, reports National Geographic.
That's equivalent to each person on Earth accumulating their own weight in stuff each week. At this rate, it's possible that human-made materials will triple the mass of all living things by 2040, reports Drew Kann for CNN.
"Given the empirical evidence on the accumulated mass of human artifacts, we can no longer deny our central role in the natural world," authors Emily Elhacham and Ron Milo, both researchers at the Weizmann Institute of Science in Israel, tell CNN. "We are already a major player and with that comes a shared responsibility."
This study bolsters the argument that we're already living in the Anthropocene, a proposed geologic period defined by humans reshaping the planet. Scientists have long debated over when the Anthropocene will officially start or if it started decades ago, reports Science.
The world is experiencing such a dramatic transition that "happens not just once in a lifetime, but once in an era," Milo tells National Geographic.