# how do scientists know how much flora/fauna species that have been discovered?

it says that only around 14% of all fauna have been discovered.

but how could we know how much we have found when we never know how much is yet to be found/or the total number? that 14% could actually be less, or even close to complete.

example : imagine there's a pool, full of different colors of balls. you are tasked to find the golden ones but never told about how many golden balls are there. let's say you have found five, how could you know the remaining number of balls? it's not that God will literally tell you "hey, there's still 20 more in there", right?

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• 4 weeks ago

To make such estimates, scientists assume their is an even distribution.

In your pool example, it would be assumed that the golden balls are evenly distributed throughout the pool.  So, if 100 Liters of water is searched and one golden ball is found, it is assumed that there is a golden ball per 100 L of water.  If the total Liters of water is estimated to be 2.5 million, then there should be 25,000 golden balls.

Of course, the golden balls might not be evenly distributed, but that assumption is made in order to make an estimation.

• Endly3 weeks agoReport

short but makes sense. "assumption" in this case makes more sense than "estimation". i was like "aaah...yes, assumption" when reading this. thank you.

• 4 weeks ago

Take a chunk of the earth, and search it like crazy for every living thing there. Count how many new species you discover compared to how many already known species you find. Repeat this many times under many circumstances, and you can build up a statistically sound model of the number of unknown species worldwide.

And no, it's not just a guess or an estimation. When done properly, you can calculate out very exactly how much uncertainty there is in your number, so you can say things like, "We are 95% certain that we have discovered between 13.2% and 14.5% of the existing species on earth."

One final point - many lay people have this underlying belief that cataloguing life forms is a major area of focus for biology, so the idea that some species could have escaped notice is baffling. This isn't true. There are only a handful of scientists out there actively looking to define and describe new species, and that's usually only as a side effect of their actual research interests. I know several scientists that have a bunch of unnamed new species sitting in their drawers for years, because they can't be bothered to write them up.

• oikoσ
Lv 7
4 weeks ago

It's done the same way that you estimate populations by removal. You have historical data and extrapolate them. There have been a couple of good papers on the subject, the titles of which escape me. One was in the journal Evolution. The other bore a title something like Homage to Santa Rita.

There are glitches caused by zoologists (mostly parasitologists) getting active. I used to take cigarette breaks with some people who worked in a parasitology lab. Conversation would go something like, "How's it going?" "Slow day; just one new genus and five new species." That can really skew the curve.

• NONAME
Lv 7
4 weeks ago

right...it is just an estimation

• Endly4 weeks agoReport

"estimation" still needs something as the base of the estimation itself. i doubt the size of the earth alone could be used as a mean of estimation