This is a first for me. I always had heard that worms were very beneficial to the ground. For one, they help prevent the ground from getting too compact. They are like living aerators. Additionally, they are supposed to help in the decomposition of grass clippings and other biodegradable matter in the yard.
However, I found out today that many of the worms we now have in North American soils are not native species
to this continent. These invasive species of worms were most likely brought here by European travelers that brought plants, and thus dirt, with them. At least in the Northern states, like Minnesota, there is no evidence that earthworms ever lived indigenously in the area.
So what's the big deal? It sounds like earthworms are good for the soil. The problem is primarily in the forested areas. Before worms, the leaves from the trees would decompose very slowly leaving a soft protective layer for small creatures and plants. Without that protective layer, we are seeing more erosion, and lower survival rates of saplings and some wildflowers.
I don't particularly like worms other than for fishing bait, but I've never thought that we should be without them completely. The article does mention some benefits of worms in more urban areas. The long and short of it is that the worms are bad for these forests but can be good for lawns and gardens. It's an interesting concept.