A new study reveals that the Earth contains a staggering one trillion species, with just one one-thousandth of 1 percent of them currently known. The team of Indiana University researchers that headed the study obtained this estimate through the intersection of massive datasets and universal scaling laws.
Using datasets from microbial, plant and animal communities from government, academic and citizen science sources, the team was able to create a dataset that represents more than 5.6 million microscopic and nonmicroscopic species stemming from 35,000 locations across the world, excluding only 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."
New microbial sampling efforts have increased over the last few years due to the realization that microorganisms were significantly under-sampled. Some new efforts include 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."
As of now, the Earth Microbiome Project, a global multidisciplinary project that aims to identify microscopic organisms, has catalogued less than 10 million species. When taking the current study into consideration, the task of identifying every microbial species on Earth seems even more daunting.
"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.
