The beauty of nature
The text presents nature as originally beautiful and pristine, only marred by human action. Indeed, before any humans arrived, the Truffula Trees and their inhabitants lived happily. This is evidenced by the awe that the Once-ler feels as soon as he steps onto the landscape. Yet bit by bit, his factory seeps some of that beauty out.
Consequences
Once the trees are cut down, there is no going back. In The Lorax, the Once-ler must live with the consequences of his actions. He is not the only one affected, however; many animals have been displaced, and even the humans in the nearby town suffer from a degraded environment. This is the great moral lesson of The Lorax: your actions have consequences, and your choices matter.
Conflict between environmental protection and economic expansion
The Lorax advocates for custodial guardianship, or taking responsibility for nature. This approach is at odds with the Once-ler's profit motive, and it ultimately loses out.
