Neuron Culture

A European nightcrawler, ready to make trouble

Eartthworms, it seems, are the new decimator, at least in Midwestern hardwood forests . Scientific American has the story:

Long considered a gardener’s friend, earthworms can loosen and aerate the soil. But the story is different in the Great Lakes region. The last Ice Age wiped out native earthworms 10,000 years ago, and ever since the Northeast forest has evolved without the crawlers, Hale says. But now earthworms are back, a product of fishers who toss their worms into the forest, of off-road vehicles and lumber trucks that carry them in the treads of their tires, and of people who bring in mulch–and any worms that might be in it–from other areas.

The worms then much away the 2-5-inch thick organic leaf layer that these forests are used to having.

As a result, some northern hardwood forests that once had a lush understory now have but a single species of native herb and virtually no tree seedlings. Evidently, earthworms change the forest soils from a fungal to a bacterial-dominated system, which speeds up the conversion of leaf detritus to mineral compounds and thereby potentially robs plants of organic nutrients.

The worms also apparently mess with the salamander population, as many of them are too big for young salamanders to eat.

This is a strange story, to be sure, and as I’ve not previously heard anything on it, I frankly wonder how widespread a problem it is. Apparently we’ll soon learn more, as the University of Minnesota ecologist featured in the story, Cindy Hale, recently got a 3-year, $397,500 federal grant to see how widespread and serious the problem really is. This strikes me as the sort of study that science ‘skeptics’ like John McCain might ridicule — $400,000 to study earthworms! But if they affect the forests the way described in this story, the impact on the forest-based industries could be large indeed.

Worth reading the whole (fairly short) story at SciAm.

Hat tip: James Hathaway

Disclosure dept: I sometimes write for Scientific American and am a contributing editor for Scientific American Mind (a nonpaying distinction).


  1. #1 MattK
    March 10, 2009

    People here in Ontario (at least those in the know) have been concerned about this for years. For those of us for whom salamanders represented the pinnacle of evolution the loss of our forest floors is a tragedy.

    see here.

    Unfortunately, I’m not confident that we will ever find a solution to this problem.

  2. #2 Paul Murray
    March 10, 2009

    All part of the great extinction event currently ongoing, caused by mankind tranferring species all around the world, where they become pests.

  3. #3 TErry
    September 8, 2010

    Earthworms do not actually eat the leaves or decaying matter. They eat the micro-organisms that breakdown the matter. They eat harmful micro-organisms too, which is beneficial for the soil.

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