National Geographic explorer and educator John Francis will speak about his experiences as an environmental activist and practitioner at an event presented by the University of Pennsylvania’s Morris Arboretum in partnership with Temple University Ambler.

Francis will give his talk, “Approaching Sustainability,” at 2 p.m. on Sunday, March 5, at Temple’s Ambler Campus Learning Center Auditorium, 580 Meetinghouse Rd., Ambler. General admission is $20, $15 for Penn cardholders or Morris Arboretum members.

Francis, who was born in Philadelphia, began his work in 1971 when, after witnessing an oil spill in San Francisco Bay, he stopped using motorized vehicles and took a vow of silence lasting 17 years.

The founder of Planetwalk, an environmental-awareness organization, Francis ended his silence on Earth Day 1990, telling the assembled crowd, “Environment is about how we treat each other.”

He served as project manager for the United States Coast Guard Oil Pollution Act of 1990 and authored Planetwalker: 17 Years of Silence, 22 Years of Walking and Ragged, and Edge of Silence: Finding Peace in a Noisy World, both published by National Geographic Books.

Additional details, including registration information, are available at the Morris Arboretum website.