The worms crawl in, the worms crawl out, the worms cause ecological devastation.

The odds are good, if you live in the contiguous United States, that you’ve never seen a native earthworm. It also turns out that the invasive European earthworms, that have been colonizing North America for centuries, are causing radical changes to the landscape. I periodically talk about the various environmental problems that would merit concern even in the absence of global warming, and this is one of those. Invasive species can do incredible amounts of damage, and often in ways that nobody sees coming. Apparently the ways in which they alter soil structure and soil chemistry decrease water availability for native plants, warm the soil, and they’re even contributing to the so-called “Insect Apocalypse”. For all I grew up thinking of worms as Good For Plants, it turns out the wrong kind of worms can cause as much damage to a forest understory as I’ve ever seen from things like garlic mustard or honeysuckle.

Tegan came across this breakdown of where the current front of the invasion is, and how it’s doing harm, so I thought I’d share it. There are also a couple links above with more information. The first link above indicates that they might help with natural carbon sequestration, but it’s unclear to me how certain that is, or how it would balance with the cascading harms done by their activity. To my knowledge, there’s not anything that folks like us can do about this at this stage, but I’ll keep an eye out for any direct action that could help. It seems like some forest makeups are hostile to European worms, so maybe there’s a way to do a little ecosystem engineering of our own, to fight back. Beyond that, this is one of the many ways in which human activity has had a huge and fascinating effect on this planet, from an ecological perspective.



  1. StevoR says

    Interesting, shared. I am guessing similar underground invasions are occurring elsewhere including in Oz.

  2. says

    I am sure that the scientists in the field are doing their job but this does make me wonder for how much of the forests not being able to rejuvenate properly are the deer to blame and how much the earthworms. Is it possible If there were not too many deer overgrazing the undergrowth, the impact of the earthworms might be even negligible or nonexistent? Maybe helping to reduce the white deer population either by culling or by helping their predators to propagate would mitigate the problem significantly. It would not be the first thing where a synergistic effect of two weak factors can lead to a big outcome.

    That is just what comes to my mind on a cursory reading, of course, I am not and I cannot become an expert on this issue.

  3. says

    I think it’s a valid concern, Charly, and I expect it’s one of the hardest parts of the job. If there are places with healthy wolf populations, and a diversity of earthworm invasion stages, then that should be one way to control for that particular factor. Ditto places that have the same deer density, but different worm-states. I do not know whether that has been done.

    It also seems that being able to measure changes to soil structure and chemistry would open up at least a couple testable hypotheses for causal factors. That said, I’m no more an expert on this than you, and it does seem like there are a near-endless number of factors that could be affecting all this.

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