john francis (born 1946) is an american environmentalist nicknamed the planetwalker. born in philadelphia, the son of a west indian immigrant, he moved to marin county, california as a young man. after witnessing the devastation caused by the 1971 san francisco bay oil spill, he stopped riding in motorized vehicles, a vow which lasted 22 years from 1972 until 1994. from 1973 until 1990, he also spent 17 years voluntarily silent. during this time he earned a ph.d. in land management and traveled extensively, walking across the entire width of the lower 48 states of the usa as well as walking to south america.