How do earthworms help the Earth?

Common earthworms burrow deep below the surface. In burrowing, worms swallow large quantities of earth that often contain vegetable remains. They are able to digest the nutritive matter of the soil, casting out the remains. The casts excreted from the worm's digestive system make the soil more fertile. The earthworm's burrowing action continually moves mineral-rich soil to the surface, and improves drainage by aerating the soil.