In 1971, John Francis witnessed a terrible oil spill. Seeing the destruction caused by the oil industry, Francis stopped traveling in motorized vehicles. Instead, he walked. In 1973, he stopped talking. Instead, he listened. While he was walking, and while he was silent, Francis traveled on foot across the entire continental US, walked to South America, and even earned a Ph.D. in Land Management. He remained out of motorized vehicles for 22 years, and silent for 17.

Now Francis is talking. What does he have to say about his life's work for the environment? What did he see during his travels? Did walking and not talking make a difference? Listen: