Environmentalists have been talking for a long time about the threat to the planet. Now, a prominent voice is directing our attention to a related threat: he says our very humanity is in peril. This week on Sea Change Radio, we welcome back author and environmental leader Bill McKibben. The founder of 350.org, McKibben most notably spearheaded the resistance to the Keystone Pipeline and launched the fast-growing fossil fuel divestment movement. His new book is Falter: Has the Human Game Begun to Play Itself Out? While his thesis may seem grim, the book includes a call to action and engagement. In our conversation we discuss the new book, how climate change activism is disrupting right wing plans, and what people can and must do to advance and support a sustainable future.