Famous for his environmental and peace activism, Kumar edited Resurgence & Ecologist magazine; founded the Schumacher College International Center for Ecological Studies; and organized pacifist, anti-nuclear weapons marches in the United States, England, France, and Russia.
When he was just nine years old, he left home and pursued the life of a Jain monk. After leaving the monastery in his teens, he studied with Gandhi follower and fellow pacifist Vinoba Bhave.
He contributed to a 2009 publication titled We Are One: A Celebration of Tribal Peoples. His other books include The Buddha and the Terrorist: The Story of Angulimala and You Are, Therefore I Am: A Declaration of Dependence.
He was born in Sri Dungargarh, Rajastan, India. He later settled in Hartland, Devon, England, where he and June Mitchell raised a daughter named Maya and a son named Mukti.
His peace walk efforts followed from the earlier pacifist activism of philosopher Bertrand Russell.