I was shocked to learn that there were few native worms in the glaciated portion of North America. I use worms indoors to compost paper and kitchen scraps. I don't think there is much chance of transfer as my garden is on the roof of an apartment. I was still surprised that my worms are essentially invaders in some parts of this country.
Thinking about all of this lead me to look up the damage done by non-native worms in North America. They have an impact on plants that once relied on the matted leaves on the forest floor. So, they can lead to more barren undergrowth. The native worms are not good at competing for some reason.
And I thought all worms were beneficial!
Still, before the most recent glaciers there were worms in these regions. So, why isn't this like turning the clock way back? In the end, after the glacier's impact fades, shouldn't there be a lot of worms again some day?
I guess sudden change is hardly ever desirable. But I'm very confused about how to identify an invaded ecosystem. Is it just based on what humans notice? Has anyone tried to make the concept more objective?