How Much Life Does Earth Host?

The number of species currently alive is a best guess at best. David Biello reports

Join Our Community of Science Lovers!


On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.


Everywhere we look, new life emerges. Bats the size of bumblebees. A roundworm that feasts on bacteria more than a kilometer underground. Even microbes that fill the air and cause rain or snow.

Scientists want to know how many species we share the planet with—especially since we're killing them off at least 100 times faster than at any period in recent geologic history.

The latest census effort guesstimates roughly 8.7 million species on Earth and notes that we know only 1.2 million of them. It’s published in the journal Public Library of Science Biology.

This effort may merely illustrate our ignorance, as the researchers extrapolated from what taxonomists have logged to date. The only real answer is the long, hard slog of searching for life everywhere and recording it when we find it. The "bar code of life" project is one such initiative, using genetics.

Even then, the tiniest life forms may remain massively undercounted. After all, there can be thousands of different microbes in a single spoonful of earth or sea. Pity the poor nematode that may vanish from the record of life before we even know it.

—David Biello

[The above text is a transcript of this podcast.]

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American

Subscribe