You see my young ones Mr. Once-Ler is not a bad guy, he was just ignorant and not willing to listen top all the trouble he's caused. He could've continued making his thneeds but only if he could use the truffula trees in moderation. He could have planted two new trees for every one he cut down. He could have kept his business small so he would not create as much smog, He could have found some where else to dump his waste so he wouldn't force all the creatures out. You see Mr. Once-Ler wasn't thing of the future in mind, he was only worried about making a buck. Now he sits alone in his shop just thinking of all the pain he's brought. There are no more trees, the skies are gray, there isn't any fresh air and the water is filled with glump, Only you can change the world, and unless more people start to care I'm afraid the forest will no long be there. So plant the last truffula seed and one day there will be a field of colorful truffula trees cleaning the air and the water, making this world a beautiful place once again. You see the trees help all living things, so please don't chop down all the truffula trees again.
the once-ler listened
In this ending of the lorax the once-ler listened he stopped cutting the trees down he postponed his manufacturing of thneeds, he waiting several years and started reproducing. Each year he'd stop to let the trees regrow and repopulate, he never wanted to chop down all the trees and the forest was more important than his business for once.