It's generally accepted that very many species have yet to be discovered, but until now nobody has devised a reliable way to find out just how many. Suggestions for total numbers have ranged from 3 million to a hundred million, but most of these have been no more than intelligent guesses.
Scientists from the Census of Marine Life devised a counting method by identifying numerical patterns linking data on known species. They reckon that there should be about 8.7 million types of living organisms, three-quarters of them animals and the rest plants.
However, since the introduction of the current classification systemby Carl Linnaeus in 1758, only a million and a quarter have been catalogued.
The scientists warn that human activity is hastening extinctions, and they note a touch wistfully, that many of the hitherto unknown species may vanish before we even know of their existence.