The United Nations Environment Program, UNEP, turns 50 years old this year. And in early June world leaders are gathering in the city where UNEP was born to commemorate this milestone in a conference known as Stockholm+50.

Maria Ivanova wrote the book on the absolutely fascinating history of the United Nations Environment Program. She is a professor of Global Governance at the University of Massachusetts Boston and author of the book "The Untold Story of the World's Leading Environmental Institution: UNEP at 50."

We kick off discussing the historical context in which UNEP was born before having a broader conversation about some of the key decisions and key moments from the 50 year history of the UN's first global environmental body.