Species of plants and animals are becoming extinct at least 1,000 times faster than they did before humans arrived on the scene, and the world is on the brink of a sixth great extinction, a new study says. The study looks at past and present rates of extinction and finds a lower rate in the past than scientists had thought. Species are now disappearing from Earth about 10 times faster than biologists had believed, said the study’s lead author, biologist Stuart Pimm of Duke University. “We are on the verge of the sixth extinction,” Pimm said from research at the Dry Tortugas. “Whether we avoid it or not will depend on our actions.” The work, published Thursday by the journal Science, was hailed as a landmark study by outside experts. Pimm’s study focused on the rate, not the number, of species disappearing from Earth. It calculated a “death rate” of how many species become extinct each year out of 1 million species. More