Not the discussion I heard (which was Wangari Maathai in conversation with Rosie Boycott), but The Guardian has a Haycast discussion for download:

Tony Juniper, director of Friends of the Earth, argues that people power can only do so much - governments need to act. He joins Wangari Maathai, Kenyan Nobel Peace Laureate and founder of the African development Green Belt Movement to discuss the gap between individual actions and international politics.