The Politics of Biodiversity - How Many Species Are Going
Majeres, Julie, The World and I
Most scientists agree that the actual number of species taxonomically identified on Earth today is 1.75 million. They also agree that this number is woefully imprecise, as they have only tallied the more obvious species, including most of the mammals and birds, while sharply undercounting the numbers of other species, such as many insects and fungi. The disagreement begins over estimates of the planet's total number of species, which range from 3.6 million to 100 million.
Ranging further, the dispute is carried into questions about the background extinction rate--reflected in the number of species lost before humans arrived. These estimates range from 3 species lost for every 10 million species per year (0.00003 percent) to biologist Edward Wilson's overly simple number of 1 extinction for every 1 million species per year (0.0001 percent).
The most consistently strident debate pertains to the estimated number of species dying above the background rate as a result of human activity. …