Though humans have shared the planet with millions of other creatures for thousands of years, we know surprisingly little about our neighbors—we don’t even know exactly how many flora and fauna call Earth home.
The National Science Foundation’s “Tree of Life” project estimates that there could be anywhere from 5 million to 100 million species on the planet, but science has only identified about 2 million.
“We’ve only touched the surface of understanding animal life,” said entomologist Brian Fisher of the California Academy of Sciences. “We’ve discovered just 10 percent of all living things on this planet.”
Environmental index
Taking an exact count of Earth’s creatures may not seem like the most important task, but taxonomy, the science of discovering, describing and categorizing living things, is “the foundation for understanding life on this planet,” Fisher said.
Though taxonomists have been cataloguing plants and animals for more than 250 years, they still have no exact answer to the question, “How many species are on Earth?”
“It’s a very simple question, but we have no simple answer,” Fisher said.
http://www.livescience.com/strangenews/070803_gm_numberspecies.html