Tim Parshall:
Over the past decade, we also seem to be getting closer to a good estimate of how many species actually exist on the planet. You would think that we would have some scientific consensus on this number, but take a look at any biology or environmental science textbook and you’ll find the same broad range quotes … between 5 and 100 million species. There’s a huge difference between 5 and 100 million! And since our current list of named species is just 1.5 million it has seemed that we have a long way to go.
However, recent scientific studies appear to be narrowing in on the lower end of that huge range … somewhere around 10 million, perhaps less (though there is still a considerable difference of opinion).