Of course, we can't miss the environmental aspects of Bartholomew and the Oobleck. The kingdom begins as an über-natural, life-giving force (what, after all, is more natural than having four seasons?), only to get all mucked up at the hands of man.
Seuss wants us to take a deep look at the ways in which we use the environment, what it gives to us, how our own desires damage it, and how we are utterly powerless in the face of its wrath thanks to our own selfishness.
Looks like Seuss was a fortuneteller, too. In more ways than one.