Todd Witcher responds to Elizabeth Kolbert's The sixth extinction: an unnatural history and explains the actions that can be taken. (Recorded December 17, 2014)

Over the last half a billion years, there have been five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. Elizabeth Kolbert draws on the work of scores of researchers in half a dozen disciplines, accompanying many of them into the field: geologists who study deep ocean cores, botanists who follow the tree line as it climbs up the Andes, marine biologists who dive off the Great Barrier Reef. The sixth extinction is likely to be mankind's most lasting legacy; as Kolbert observes, it compels us to rethink the fundamental question of what it means to be human.

"This a great book that takes a look at the biological issues we face in today’s world," Witcher says. "It should renew your interest in conservation and move you to take action." Mr. Witcher is the executive director of Discover Life in America, the nonprofit organization coordinating the All Taxa Biodiversity Inventory in the Great Smoky Mountains National Park.