In this lecture Mario Molina defines the causes of global warming as a direct result of human behavior. He points out that local environmental concerns have become global ones and reminds us that "we only have one planet." Eric Chivian discusses the loss of biological diversity and its implications for the planet. He explains for example, why Lyme disease is more prevalent in the northeast, lessons to be learned from hibernating bears and the natural sources for some of the worlds most frequently prescribed drugs. He takes on SUV's unnecessary gadgets, and wasteful consumption.