June 15 – OK Biome

Today’s Factismal: Biologists have identified fewer than 15% of all of the species on Earth.

One of the most important questions in biology is “how many species can a given area sustain?” Knowing the answer to that question tells you about how energy- and nutrient-rich the area is (more species need more energy and nutrients), how long the area has been habitable (more species take more time to develop), and most importantly how well the area can withstand a change in the environment (more species mean that the death of some won’t kill them all). But it is surprisingly hard to answer that question for the Earth as a whole; we’re still not sure how many species there are on the planet even though we’ve been identifying them for more than 4,000 years and have found more than 1,300,000 species!

A "Tree of Life" showing the number of known species (Image courtesy iTOL)

A “Tree of Life” showing the number of known species
(Image courtesy iTOL)

Part of the reason that it is a difficult question is because most of the species on Earth are microscopic. For example, there are more species of bacteria in your intestine than there are species of bats across the world! A teaspoon of soil may contain up to 10,000 different species of bacteria, not to mention all of the fungi, protists, plants, and earthworms. (It is a wonder that there is any room in the soil for dirt.) And because most of these tiny species have very few regular structures, the species must be identified through DNA analysis, which is notoriously expensive and time consuming.

But the larger part of the reason for the uncertainty is because the different places to live on Earth (what biologists call “biomes“) are so, well, different. The creatures and plants that live in the deepest part of the ocean can’t survive in the Saharah desert and none of those critters could live two miles down in the Earth. As a result, though we have a fairly good idea of how many species of big things that live in well-studied areas (read “popular places”), we are still discovering how many species there are in more remote regions (read “places without beer”).

Four tiny plankton; the largest is about the size of a grain of rice (Image courtesy John R. Dolan, NOAA)

There are a lot more of these in the world than there are elephants
(Image courtesy John R. Dolan, NOAA)

Despite this, scientists have estimated how many undiscovered species there are. Those estimates range from a mere 7,400,000 species (six times as many as we have identified) to as many as 100,000,000 species (seventy-seven times as many as we have identified!). That means that we have discovered fewer than 15% of all the species that share this planet with us. If the larger number of unknown species is true, then we have found just 1.3% of all living species on Earth! And, given that biologists only discover about 15,000 new species each year, that means that they will be identifying new species for at least 500 years and possibly for as long as 6,700 years!


Of course, there are ways to speed things up. And chief among these is getting more information and more help. And that’s where citizen scientists like you come in! By submitting photos and locations of animals to Project NOAH, we can help biologists discover new species and (equally importantly) map out the distribution of known species. If you’d like to add a picture and lend a hand to the biologists, then head on over to:

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