The number of ants on Earth has a mass greater than all birds and mammals combined

Caption

In this photo provided by the U.S. Fish and Wildlife Service, yellow crazy ants are seen in a bait testing efficacy trial at the Johnston Atoll National Wildlife Refuge in December, 2015. An invasive species known as the yellow crazy ant has been eradicated from the remote U.S. atoll in the Pacific. / AP

For every human on Earth, there are estimated to be about 2.5 million ants — or 20 quadrillion in total.

A new study published by researchers at both the University of Hong Kong and University of Würzburg in Germany attempts to count the total number of ground-dwelling and tree-dwelling ants. The final figure is equal to 1 trillion times 20,000, and the insects' total mass exceeds that of all birds and mammals combined, and makes up about a fifth of humans' total biomass.

And that's just a conservative estimate.

"Knowledge on the distribution and abundance of organisms is fundamental to understanding their roles within ecosystems and their ecological importance for other taxa," the study says. "Such knowledge is currently lacking for insects, which have long been regarded as the "little things that run the world."

The scientists analyzed 489 studies across all continents, biomes and habitats that used methods such as studying leaf litter, which help study tree-dwelling ants, and setting pitfall traps, which is done by placing a beaker into the ground so that the top is level with the surface, causing ground-dwelling ants to fall in.

There are 15,700 known ant species and subspecies. These six-legged creatures serve vital roles in the ecosystem, as they help spread plant seeds, accelerate decomposition and support the food chain as both predator and prey.

Despite their grand numbers, though, their populations are declining due to habitat destruction, invasive species and climate change.

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