Another reason to plant a tree to help the planet: They act as mini air-conditioners for your home environment. In the hot summer months, trees pool water from the ground to keep them healthy and alive. As the water pumps up through the trunk, it evaporates through the leaves. The water acts as a cooling mechanism for the tree and it also cools down the area around it. The more trees around your home, the more cooling effect it has for you. Now how cool is that?