In his book 'What On Earth Evolved' Christopher Lloyd ranked earthworms as number one on his list of 100 of the most important living organisms. Charles Darwin also stated the lowly earthworm to be one of the most important of living animals.
Worms are an indicator of healthy, fertile soil. There are upwards of 4,400 different species of worms world wide, of which about 200 are native to North America. Areas cover during that last ice age did not have worms until brought in with settlers from Europe. That aside, earthworms are amazing creatures that improve and enhance the quality of soil. They burrow, shred and leave castings. They improve the soil, helping the growth of healthy plants occur naturally with out the need for chemical, synthetic fertilizers. Healthy plants provide healthy food.