So as I said yesterday, you’ll be hearing more from me about Circus of the Spineless in the coming days. It’s a three-ring blog circus that shines a spotline on all kinds of invertebrate-related blogging going on out there. Today, pay a visit to Bootstrap Analysis (Chronicles and Musings of a Field Biologist), where you’ll learn all about the non-native species of earthworms that are transforming some of our Northern forests.
Why only forests in the North? Because those areas were covered by a glacier during the last Ice Age about 10,000 years ago. The ice wiped out whatever native worms were there. The forests that grew after the glaciers receeded were earthworm-free. As non-native worms moved into the area (and most worms in your backyard, including red wigglers and nightcrawlers, are actually European worms), they gobbled up all the leaves that covered the forest floor–called the duff layer–and that changed what plants could grow in the forest.
Does this mean that non-native worms are an unmitigated evil? Not necessarily. We don’t know whether they cause harm in other forests, mostly because earthworm science is an underfunded field and it just hasn’t been studied. And if you grow non-native plants in your garden, and bring in non-native soil–well, you already have a somewhat artificial environment. A worm population migrates very slowly–only a few yards a year–so it’s not as if worms in your backyard are going to end up in a forest miles away anytime soon anyway.
When I dug up different species of earthworms in my own backyard and sent them to a taxonomist to be identified, they all turned out to be non-native European species.