In 1971 an oil spill in San Francisco Bay jarred John Francis’ comfortable life. He joined the volunteers who scrubbed the beaches and fought to save birds and sea creatures, but felt the need to make a deeper, more personal commitment. To affirm his responsibility to our planet, he stopped using motorized vehicles and began walking wherever he went. A few months later he took a vow of silence that would last 17 years. In 2008, National Geographic published Francis’s stirring memoir Planetwalker: 22 Years of Walking; 17 Years of Silence. In 2010, Francis became the first National Geographic Education Fellow.