Researchers find that Earth may be home to 1 trillion species

NSF | MAY 10, 2016

Earth could contain nearly 1 trillion species, with only one-thousandth of 1 percent now identified, according to the results of a new study.

Grand Prismatic Spring in Yellowstone; such hot pools often bubble with undiscovered microbes. Image credit: Brocken Inaglory/Wikipedia (CC BY-SA 3.0)

The scientists combined microbial, plant and animal datasets from government, academic and citizen science sources, resulting in the largest compilation of its kind.

Altogether, these data represent more than 5.6 million microscopic and non-microscopic species from 35,000 locations across all the world's oceans and continents, except Antarctica.

This research offers a view of the extensive diversity of microbes on Earth. It also highlights how much of that diversity still remains to be discovered and described.

Microbial species are forms of life too small to be seen with the naked eye, including single-celled organisms such as bacteria and archaea, as well as certain fungi. Many earlier attempts to estimate the number of species on Earth ignored microorganisms or were informed by older datasets based on biased techniques or questionable extrapolations.

The study's inventory of data sources includes 20,376 sampling efforts on bacteria, archaea and microscopic fungi, as well as 14,862 sampling efforts on communities of trees, birds and mammals.

The researchers found that the abundance of the most dominant species scales with the total number of individuals across 30 orders of magnitude, making it the most expansive scaling law in biology. Scaling laws, like that discovered by the scientists, are known to accurately predict species numbers for plant and animal communities. For example, the number of species scales with the area of a landscape.

The study's results also suggest that identifying every microbial species on Earth presents a huge challenge. Of those species cataloged, only about 10,000 have ever been grown in a lab, and fewer than 100,000 have classified genetic sequences. Our results show that this leaves 100,000 times more microorganisms awaiting discovery and 100 million to be fully explored.

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