Human-made objects now weigh more than every living thing on Earth, Israeli scientists have calculated.
They reported that in the year 1900, human-made objects and infrastructure corresponded to just three percent of the total weight of plants, animals and other living things. But 120 years later, human-made mass, comprising buildings, roads, garbage, and everything else made by people, newly outweighs this so-called biomass.
“Right now, we’re at the point in history when human impact on the earth is so dominant that it weighs more than living biomass,” Prof. Ron Milo, a systems biologist, told The Times of Israel, adding this should be a “wake-up call” for environmental awareness.
His research notes that humans, despite having made such an impact on the earth, make up just 0.01% of its biomass, compared to plants at 82% and bacteria at 13%.
In a new peer-reviewed article in the journal Nature, Milo’s team from the Weizmann Institute of Science found that with people constantly reducing living biomass and adding human-made mass, 2020 is the approximate date of the “crossover.” Around now, living biomass weighs approximately 1 teratonne, and human-made mass weighs in at around 1.1 teratonnes, he reported. A teratonne is a trillion metric tonnes, and a metric tonne is about 1.1 tons.
He found that one particular human-made material, plastic, now weighs double the mass of all animals. For every person on Earth, mass that is equivalent to more than their body weight is produced each week, he said.
“People like to say that while humanity produces a lot of ‘stuff,’ we’re really only a speck on the earth, and the amount isn’t so significant,” Milo told The Times of Israel. “This study shows, in a rigorous manner, that we are a dominant force and that we can’t hide behind this notion any more.
“Rather, we have a responsibility to think about things we’re doing and the effect we’re having. This finding should make everyone ponder and think what they can do.”
The Weizmann team has been working for years on calculating the weight of living biomass, using a range of data, including estimates of the mass of trees as calculated from satellite images of Earth, computer analysis of the amount of vegetation on Earth, and gene sequencing. Statistics on human-made mass were mostly drawn from existing data compiled by academics in Austria.
Milo wrote in his paper that if current trends continue, human-made mass, known as anthropogenic mass, will be double and triple living biomass in the coming decades.