If you allow a creek to go back to being a creek, if you let the trees and the bramble get overgrown, and you let the stream overrun its banks whenever it wants to, the wetland will take care of itself. The water that trickles into the ocean will be clean and pristine if everything is just left alone to work the way it was designed to work. Earthworms have shown that they can take care of the soil in the same way that a wetland takes care of the water. Nature regenerates. It Cleans. It hides a multitude of sins.
Amy  Stewart, The Earth Moved: On the Remarkable Achievements of Earthworms
animal-science, biology, earth-science, earthworm