Their constant burrowing causes air and water to reach deeper into the ground. The casings, which are made of mostly soil, are filled with enough nutrients to enrich the soil around them. However, they cannot stay immersed for a long period of time. In order to avoid dying in flooded burrows, earthworms crawl out and become disoriented because of the vibration of rainstorms. The earthworms life hasn't changed much over the years.
Gardeners often buy worms in large stock in order to increase the organic content of soil.
Two types of earthworms are commonly used in composting and casting production. There are a large group of people that privately breed earthworms. Some include fishermen, but more than a handful keep worm farms and the worm families they contain, as pets. The Ice Age almost entirely wiped out the earthworm population. Thanks to a few traveling Europeans carrying houseplants, today, the earthworm exists and great numbers and used for a multitude of chores.