Which one covers more of our Earth: snow or trees? Well, there are about 57 million square miles of land. Of that, scientists have used photos from "satellites" in space to map our forests. They found that trees cover about 3/10ths of all land, or 17,200,000 square miles (17.2 million). Meanwhile, people who study the weather have found that 17,800,000 million square miles of land have snow cover. So it's almost a tie!