"The Lorax" is the story of a character by the same name, a passionate environmentalist who fights against the Once-ler, a capitalist who cuts down Truffula Trees, using them to make garmets called "Thneeds" that the Once-ler then sells by convincing the public that they "need" them. As the Once-ler cuts down the Truffula Trees, the area's other inhabitants – the Swomee-Swans, Humming-Fish, and Brown Bar-ba-loots among them – leave due to the changing environment, which is left with no trees and a thick cloud of smog overhead.
During the Once-ler's campaign, the Lorax constantly challenges the capitalist:
The Lorax: I am the Lorax. I speak for the trees. I speak for the trees, for the trees have no tongues. And I'm asking you sir, at the top of my lungs - that thing! That horrible thing that I see! What's that thing you've made out of my Truffula Tree?Throughout the story, the Lorax keeps speaking for the trees, but "nobody listens too much, don't you know." The Once-ler does not listen until he cuts down the last tree and realizes he is left with no resources to keep his business running. Once he is left with only the Once-ler and a poisoned environment, the Lorax floats away through a hole in the smog, never to return unless his home is back to what it was.The Once-ler: Look, Lorax, calm down. There's no cause for alarm. I chopped just one tree, I'm doing no harm. This thing is most useful! This thing is a "Thneed." A Thneed, a fine something that all people need! It's a shirt. It's a sock. It's a glove! It's a hat! But it has other uses, yes, far beyond that. You can use it for carpets, for pillows, for sheets, for curtains! Or covers for bicycle seats!
The Lorax: Sir, you're crazy. You're crazy with greed. There's no one on earth who will buy that fool Thneed!
[a man drives by, buys the Thneed and pays the Once-ler]
The Once-ler: The birth of an industry, you poor, stupid guy! You telling me what the public will buy?
The Once-ler, meanwhile, has a change of heart and passes on one last Truffula Tree seed to a young boy, who is told to restore the area to its original state so the Lorax, the Brown Bar-ba-loots, Humming-Fish, Swomee-Swans, and all the rest can return.
The story is considered the most controversial of the Dr. Seuss collection since it contains pro-environment, anti-industry sentiments. It is by far one of the most "adult" Dr. Seuss stories, and unlike many others, does not end with an overtly happy ending. What it does leave the reader with is a mandate from the Lorax, who reminds everyone that unless they fight against industry to save the environment, it will never be protected.
The Once-ler: And all that the Lorax left here in this mess was a small pile of rocks with one word.Boy: [reading it] "Unless?"
The Once-ler: Yes. "Unless."
Boy: What's an unless!
The Once-ler: Just a far away word...just a far away thought...
Boy: A thought about what? About something I ought?
The Once-ler: Well...a thought about something that somebody ought, a thought about something...that somebody...ought. Unless someone like you cares a whole awful lot, nothing's going to get better. It's not.