Not your typical preachy eyefest; although it is absolutely beautiful. The conservation message comes across visually, and through interviews with some of the humblest and most interesting people you will ever see on television. The first season is mostly set in Indonesia, a country I know much about. So I can safely vouch for the accuracy of the commentary, the enormity of the problems mentioned, and the jaw dropping beauty of the nature in this part of the world.
And it has perhaps the most haunting opening song ever written for a series.