1 trillion species present on Earth, 99.999% still to be discovered

A largest-ever analysis of microbial data has suggested that there may be around one trillion species on the Earth and 99.999 per cent of them are still undiscovered. Researchers at Indiana University in the US combined microbial, plant and animal community datasets from government, academic and citizen science sources, resulting in the largest compilation of its kind.

These data represent over 5.6 million microscopic and non-microscopic species from 35,000 locations across all the world’s oceans and continents, except Antarctica. “Estimating the number of species on Earth is among the great challenges in biology,” said Kenneth J Locey, a postdoctoral fellow in the IU Bloomington College of Arts and Sciences’ Department of Biology.

“Our study combines the largest available datasets with ecological models and new ecological rules for how biodiversity relates to abundance. This gave us a new and rigorous estimate for the number of microbial species on Earth,” said Locey. “Until recently, we’ve lacked the tools to truly estimate the number of microbial species in the natural environment,” he said.

“Many earlier attempts to estimate the number of species on Earth simply ignored microorganisms or were informed by older datasets that were based on biased techniques or questionable extrapolations,” said Jay T Lennon, associate professor at the department.

“Until now, we haven’t known whether aspects of biodiversity scale with something as simple as the abundance of organisms,” Locey added. “As it turns out, the relationships are not only simple but powerful, resulting in the estimate of upwards of one trillion species,”  he said.

The study’s results also suggest that actually identifying every microbial species on Earth is an almost unimaginably huge challenge. The Earth Microbiome Project - a global multidisciplinary project to identify microscope organisms - has so far catalogued less than 10 million species. “Of those catalogued species, only about 10,000 have ever been grown in a lab, and fewer than 100,000 have classified sequences,” Lennon said.

“Our results show that this leaves 100,000 times more microorganisms awaiting discovery - and 100 million to be fully explored. Microbial biodiversity, it appears, is greater than ever imagined,” said Lennon. The research was published in the journal Proceedings of the National Academy of Sciences.