Most people don’t think much about earthworms, but gardeners do, and most gardeners think that worms have always been in our soils, but they haven’t. Canada and the northern states of the US had no earthworms after the last glaciation until the Europeans showed up.
It is believed that earthworms first arrived in the US around the seventeenth century. It’s thought that they arrived in the soil that was used as ballast on the ships coming from England. Their arrival changed forest ecosystems forever as they chewed their way through the leaf litter on the forest floor.
Some forest ecologists blame these European earthworm immigrants for the demise of some species of salamanders and ground-nesting birds, animals that depend on the forest leaf litter for habitat.
Earthworms are world travelers. They are slow to get around by their own means, traveling at a rate of about a mile a century, but it is known that they also move around to different parts of the world through the worldwide sales of fishing bait.
Today, gardeners lacking earthworms in their soil, pay to have them brought in. Many people have worm beds & bins, and there are commercial worm farms scattered throughout the country. Earthworms are instrumental in rebuilding soil health. I have been raising earthworms for about 3 years now, starting indoors, and now tending to them outdoors, under my compost pile. It makes me smile when I’m working in my garden soil and come across an earthworm. For that reason, I use my hands to plant and move soil around as much as possible to prevent killing them.
In my opinion, the accidental introduction of earthworms to the US was one of the best things that ever happened to our soils and they have contributed far more than we have lost if anything.