The Planeteers show what can happen to the environment if we continue to produce a lot of trash and waste without thinking about the long term effects of it. They show what happens if people don't follow the Three R's or don't put in a concerted effort to reduce trash.
The Planeteers are called by Gaia to stop a new villain, Sly Sludge from polluting the Earth with another one of his trash dumping schemes. When the Planeteers confront Sludge, he tells them that he no longer dumps trash and has found the answer to the problem of waste management forever. He "demonstrates" by having a machine that shoots intense beams of light supposedly shrink the trash, but unbeknownst to the planeteers, it's all smoke and mirrors.