"The 2009 edition of the IUCN Red List of Threatened Species was released today, and the news isn't good: 17,291 species out of 47,677 assessed species, or 36 percent, are threatened with extinction.

Science currently recognizes around 1.8 million species on Earth (out of an estimated five million to 30 million total species -- the true total remains unknown). But the health of the vast majority of those known  species has yet to be assessed. Even among those on the IUCN's list, 14 percent lack enough information to judge their health (or threat level) in the wild."

John Platt reports for Scientific American November 2, 2009. [2]