Some forest fires protect big trees. They do this by burning away underbrush*. Underbrush grows around the base of big trees, and too much of it can hurt them. It steals their water. And it takes up their space. Forest fires help by clearing the underbrush away, leaving the big trees unharmed. With the underbrush gone, the big trees have more water. They also have more space. This helps them to survive and grow.