According to researchers from the Indiana University, earth could be home to nearly one trillion species with only one-thousandth of one percent now identified.
The study's authors are Jay T. Lennon, associate professor in the IU Bloomington College of Arts and Sciences' Department of Biology, and Kenneth J. Locey, a postdoctoral fellow in the department.
The IU scientists combined microbial, plant and animal community datasets from the government, academic and citizen science sources, resulting in the largest compilation of its kind.
Altogether, these data represent over 5.6 million microscopic and nonmicroscopic species from 35,000 locations across the world's oceans and continents, except Antarctica.
Lennon said estimating the number of species on earth is among the great challenges in 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," he added.
Researchers found the microbial species are all forms of life too small to be seen with the naked eye, including all single-celled organisms such as bacteria and archaea as well as certain fungi.
The realization that micro-organisms were significantly under-sampled caused an explosion in new microbial sampling efforts over the past several years, including the collection of human-related microorganisms by the National Institutes of Health's Human Microbiome Project, marine microorganisms by the Tara Oceans Expedition and aquatic, terrestrial and host-related microorganisms by the earth Microbiome Project.
The results of the study suggested that actually identifying every microbial species on earth is an unimaginably huge challenge. To put the task in perspective, the Earth Microbiome Project -- a global multidisciplinary project to identify microscope organisms -- has so far cataloged less than 10 million species.
The study is published is the journal of Proceedings of the National Academy of Sciences.
