Have a class discussion about the planet and its problems. Ask students to describe what they think are the most serious problems today. Why do they think the ones they've cited are serious? How do they know the problems are serious? You may want to bring in a newspaper for one day only or videotape the previous night's newscast and have the class pick out news stories representing the problems discussed in the brainstorming session. Make a list of the problems the class identifies. Are these problems global or localized? Make a chart showing what parts of the world are affected by these problems. If possible, rank them in order of "perceived" seriousness according to criteria set out by the students. Try and categorize the identified problems, i.e., natural, man-made, environmental, territorial, racial, social, political etc.