When the Once-ler stops along his travels to utilize one of the many Truffula Trees to make a Thneed the Lorax intervenes on behalf of the trees. The Once-ler replied that it's only one tree until he sold his Thneed for a hefty proffit. He then called all his family and they chopped down more and more to make more Thneeds.
I haven't read a Dr Seuss book in probably 30 years and was entertained and amazed at the message behind this book. This is not a simple children's book, don't let the silly rhyming made up words fool you. This is a message about capitalism and greed in addition to quite the environmental stand.
When the Once-ler realized he could make so much money on the Thneeds he was creating he did whatever he could to make more. The Lorax intervened on behalf of the trees begging the Once-ler to cease. The Once-ler replied "I'm being quite useful. This thing is a Thneed. A Thneed's a Fine-Something-That-All-People-Need!" And so he ignored the plight of the trees. Later the Lorax would come back 3 more times to speak for the Brown Bar-ba-loots who's food supply was dwindling with each chopped tree, the Swomee-Swans who could no longer sing with all the smog in their throats, and the Humming-Fish who's gills were getting all gummed because the water was so polluted. All the animals had to find new homes and when the last of the Truffula Trees was chopped, the Once-ler's family all left too and he was left with buildings falling down, polluted water and air and very much alone with only the last word the Lorax said to him for comfort. "Unless."
I loved this message. Dr. Seuss wrote this book in 1971 the message is more dire 40 years later.
There is some hope though for the Once-ler had a visitor much later who he gave the very last Truffula Seed to. The boy was told to plant a new Truffula Tree and treat it with care. To give it clean water and feed it fresh air. From one little seed a forest can grow but cannot Unless someone cares.