Have you ever been in a place where there were lots of buildings but no trees? New housing developments or parts of a city that have been neglected for a long time may not have the shady spots and fresh air that trees give. As trees breathe, they let out oxygen that humans and animals need to survive. Their roots hold the ground together, making sure the soil doesn't blow away in the wind. When a tree dies naturally in the forest, its wood becomes a home for insects and a cafeteria for the hungry birds who eat those insects. Trees provide so many good things for the Earth.