Chapter 17.1, Problem 1HYEW

One way to determine the number of species on Earth might be to simply count them. You could comb the scientific literature to find all the species that scientists have discovered and named, and then tally up the total number. One attempt to do just that, the Catalogue of Life project, has compiled an online searchable database that listed 1,612,941 species as of 2015. But even the Catalogue of Life can’t tell you how many species are on Earth.

Why doesn’t counting work? Because most of the planet’s species remain undiscovered. Relatively few scientists axe engaged in the search for new species, and nearly all undiscovered species are small and inconspicuous, or live in poorly explored habitats such as the floor of the ocean or the topmost branches of tropical rain forests. So no one knows the actual number of species on Earth. But biologists agree that the number must be much higher than the number of named species. A commonly held view is that the actual number is close to 8.7 million, the number estimated by a recent analysts that used sophisticated statistical methods to extrapolate past trends in species discovery.

How Many Species Inhabit the Planet?