Link: http://news.yahoo.com/s/afp/20110304/ts_afp/environmentbiodiversityextinction_20110304055833

Mankind may have unleashed the sixth known mass extinction in Earth's history, according to a paper released by the science journal Nature. Over the past 540 million years, five mega-wipeouts of species have occurred through naturally-induced events. But the new threat is man-made, inflicted by habitation loss, over-hunting, over-fishing, the spread of germs and viruses and introduced species, and by climate change caused by fossil-fuel greenhouse gases, says the study.