There are 8.7 million species on earth

Ever since I started studying biology, sometime last century, I (as well as many smarter minds) have wondered how many species are there? Best guesses have been varied widely from 1 to 100 million. But now we know the answer. There are 8.7 million species on earth (plus or minus 1.3 million)!

On 23 August, PLoS Biology published a landmark paper: “How Many Species Are There on Earth and in the Ocean?” by Camilo Mora, Derek P. Tittensor, Sina Adl, Alastair G. B. Simpson, and Boris Worm.

The work undertaken is astonishing and the methods used to arrive at the final estimation are complex, as you would expect for a task of this magnitude. Calculations of the number of species on Earth were based on the classification of all currently valid species. The authors accounted for higher taxa yet to be discovered using statistical models.Then the predicted number of taxa at each taxonomic rank down to genus was regressed against the numerical rank, and the fitted models used to predict the number of species. You can download a copy of the paper from the PloS biology web site

As of today, 13 October, the paper has been viewed more than 34,000 times. I think this may be a record for a paper on biodiversity.

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