Earth: Home to 1 Trillion Microbial Species

A new analysis of microbial data estimates that the world is home to 1 trillion species—of which only 0.001 percent have been discovered.

Written byCatherine Offord

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WIKIMEDIA, NASAResearchers at Indiana University have combined scaling laws with a model of biodiversity to produce a new estimate of the number of microbial species on Earth: somewhere between 10¹¹ and 10¹², or between 100 billion and 1 trillion. Given the current number of catalogued species stands at around 10⁷, the researchers predict that around 99.999 percent of microbial species are left to discover. The findings were published on Monday (May 2) in PNAS.

“Estimating the number of species on Earth is among the great challenges in biology,” study coauthor Jay Lennon of Indiana said in a statement. “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.”

The study compiled data from 20,376 surveys of bacteria, archaea, and microscopic fungi—plus 14,862 sampling efforts on tree, bird, and mammals communities—from 35,000 locations worldwide. After demonstrating that the abundance of the most dominant ocean bacterial species scales with the total number of individuals across 30 orders of magnitude, the researchers used these data to predict the existence of around one trillion microbial species worldwide.

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Meet the Author

Catherine Offord
After undergraduate research with spiders at the University of Oxford and graduate research with ants at Princeton University, Catherine left arthropods and academia to become a science journalist. She has worked in various guises at The Scientist since 2016. As Senior Editor, she wrote articles for the online and print publications, and edited the magazine’s Notebook, Careers, and Bio Business sections. She reports on subjects ranging from cellular and molecular biology to research misconduct and science policy. Find more of her work at her website.
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