In this episode, we speak with David Biello, environmental journalist and author of the book “The Unnatural World: The Race to Remake Civilization in Earth’s Newest Age”. The book details the many ways human activity has altered our planet, often for the worse, and examines efforts to rollback those alterations, or at least lessen their impact. Read an excerpt from David's book on the NATURE website: http://www.pbs.org/wnet/nature/blog/could-we-bring-back-the-passenger-pigeon-or-other-extinct-species/