What is the mother going to do tomorrow?

M: What are you doing, Mum?
W: I’m getting something ready for tomorrow. Tomorrow is Tree-planting Day.
M: Tree-planting Day? What is that for? What do people do on this day, Mum?
W: A great number of people will go and plant trees.
M: Why do they do that?
W: To make the earth more beautiful. And to make our life better.
M: But I often see people on TV cut down many big trees. Why do they do that, Mum?
W: Hm, to make paper, build houses, and to make our life better.
M: To make our life better, too? I just don’t understand. Mum, why do many people go and plant trees while some others go and cut them down when they grow higher? It doesn’ t make any sense to me
W: Oh, my dear son. It’ s hard to explain to you. When you grow up, you will understand. Just remember trees are very important to us.