Earth Protect Blog

WASHINGTON » When you weigh all life on Earth, billions of humans don’t amount to much compared to trees, earthworms or even viruses. But we really know how to throw what little weight we have around, according to a first-of-its-kind global census of the footprint of life on the planet.

Humans only add up to about one ten-thousandth of the life on Earth, measured by the dry weight of the carbon that makes up the structure of all living things, also known as biomass.

The planet’s real heavyweights are plants. They outweigh people by about 7,500 to 1, and make up more than 80 percent of the world’s biomass, a study in Monday’s Proceedings of the National Academy of Sciences said.

Bacteria are nearly 13 percent of the world’s biomass. Fungi — yeast, mold and mushrooms — make up about 2 percent. These estimates aren’t very exact, the real numbers could be more or less, but they give a sense of proportion, said study lead author Ron Milo, a biologist at the Weizmann Institute of Science in Israel.

“The fact that the biomass of fungi exceeds that of all animals sort of puts us in our place,” said Harvard evolutionary biology professor James Hanken, who wasn’t part of the study.

Still, humans have an outsized influence on its more massive fellow creatures. Since civilization started, humans helped cut the total weight of plants by half and wild mammals by 85 percent, the study said.

— The Associated Press