Earth Hosts One Trillion Species, Most Of Them Are Undiscovered

The earth contains one trillion species, with just one-thousandth of 1 percent revealed to humans. A team of Indiana University researchers understood this estimate by intersecting huge datasets and universal scaling laws.

The team used datasets from microbial, plant and animal communities from various government, academic and citizen science sources. It gathered information and created a database that represented more than 5.6 million microscopic and nonmicroscopic species from 35,000 areas across the world, except Antarctica.

"Estimating the number of species on Earth is among the great challenges in biology," said Jay Lennon, a professor at Indiana University and co-author of the study. "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.

"Until recently, we've lacked the tools to truly estimate the number of microbial species in the natural environment. The advent of new genetic sequencing technology provides an unprecedentedly large pool of new information."

Some new efforts at increasing the microbial samples have been contributed by the National Institutes of Health's Human Microbiome Project, the Tara Oceans Expedition and the Earth Microbiome Project.

"Older estimates were based on efforts that dramatically under-sampled the diversity of microorganisms," Lennon said. "Before high-throughput sequencing, scientists would characterize diversity based on 100 individuals, when we know that a gram of soil contains up to a billion organisms, and the total number on Earth is over 20 orders of magnitude greater."

The Earth Microbiome Project, a global multidisciplinary project that is trying to identify microscopic organisms, has recorded less than 10 million species. Identifying more species to document every species on earth is a huge and overwhelming project.

"Of those cataloged 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."

The findings were published in the March 30 issue of the Proceedings of the National Academy of Sciences.