"The Man Who Planted Trees" was a book I read long ago. This is an animated short that sticks with you, particularly if you get the message. Strangely enough, my school had given it out as a graduation gift in elementary, middle and high school - so I have 3 copies of the book lying around somewhere. It’s simple enough for kids to grasp and for adults to ponder the significance of it.
Also, there are a few examples of some non-fictional characters, planting over a thousand acres of trees: http://www.huffingtonpost.com/2012/04/03/indian-man-jadav-molai-pa_n_1399930.html