Here is section taken from an educational textbook for teachers, specifically talking about John Denver's contributions through his music. It was in an internationally available environmental text book that corresponds with workshops teaching teachers how to teach environmental education.
Art reflects the artist.
It may also influence one who sees, hears or feels the art. Social attitudes toward environmental issues are affected by the communications media, including the classical and popular arts. Historical and contemproary artists have expressed their views about issues, including environmental issues, and have influenced others in the process. Artists may influence different people in different ways. John Denver spoke and sang to the US Congress in Washington, DC, on the Alaska Land Bill issue.