Many people fail to realize that trees are what keep us alive on earth, and will continue to do so for the decades and centuries to come. Trees excrete useful waste and take in our own, which perpetuates an ongoing cycle for us to thrive in. Our waste that the trees and plants take in, are needed for them to breathe, and provide for their basic functions. In return, the plant waste, as we know as oxygen or air, is excreted into the air. This allows us to breathe freely.
Despite this, many people take plants for granted, and when this happens, it can have dire consequences. Cutting down trees, for example, is what causes humans like you and me to get closer and closer to extinction. When trees are cut down, they die and when they die, they stop producing the air that we need to survive as members of the human race.
So if there are no more trees, there are no more people. Without trees to make air, and without air for us to breathe, we get closer and closer to dying.