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the worm has turned

A

by bruce stutz

s a volunteer for a survey

of woodland amphibians and reptiles in eastern Pennsylvania, I was given

the job of counting all the red-backed salamanders that I found beneath rocks and fallen tree limbs. I found plenty, which was no surprise. In some hardwood forests, the combined mass of these lithe, delicate, and streamlined little amphibians can outweigh that of all the birds and small mammals put together. What was remarkable, however, was the number of

2 6 onearth

spring 2014

earthworms I was uncovering—dense, wriggling caches of sometimes a dozen or more. When, with some smugness, I mentioned to the biologist in charge that all these earthworms were a sure sign that this was “good soil,” his sharp response jolted me: these earthworms, he said, were wrecking this forest, just as earthworms were wrecking forests all the way from the Great Smokies to the Great Lakes. Wait—earthworms? The nightcrawlers I’d dug up as a kid? The red wigglers I’d bought by the boxful from bait shop coolers and gas station vending machines, the ones that I threaded on hooks for my own kids when I took them fishing, or that appeared on lawns after drenching summer rains? Like many people, I had been laboring for years under the impression that earthworms were completely beneficent—that their presence in your vegetable garden or flower beds meant that you were good to go. Lots of gardeners, I knew, even bought them mail order—from actual worm farms, no less!—to add to their precious compost piles. The reputation of these creatures, so far as I could tell, was as the condicio sine qua non of no-till organic agriculture: burrowing through hard and compacted soils, digesting fields full of vegetable matter, and converting it all into nutrient-rich cropland. No less a scientist than Charles Darwin devoted nearly 40 years to the study of earthworms. He greatly admired the industriousness of these blind and deaf creatures as they burrowed deeply through the soil, their prodigious appetites, and the surfeit of castings—the soil-like excretions—that they left behind. Darwin concluded that earthworms had engineered much of the natural landscape: the gradual accumulation of all those castings, he believed, was the terrestrial equivalent of the accumulation of calcareous skeletons that formed the earth’s coral reefs over many eons. In his 1881 book, The Formation of Vegetable Mould, Through the Actions of Worms, With Observations on Their Habits, he wrote, “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.” Ecosystem builders! Peerless composters! Great fish bait! So why, among the forest ecologists with whom I spoke, couldn’t I find one with a kind word to say about earthworms? Most of them instead simply echoed the sentiments of Timothy Fahey, a professor in the department of natural resources at Cornell University, who calls earthworms—in North American forest settings, at least—“more of a curse than a blessing.” The reason he and many of his colleagues feel this way is rooted in a surprising fact: of the nearly 200 different taxa of earthworms found in Canada and the United States, almost one-third are actually invasive species. And the concentration of non-native earthworm species is far greater in the temperate and temperate-coniferous forests of North America, where almost none of the earthworm species are native. Their invasion commenced in the seventeenth century, when European ship captains first began dumping their ballasts of foreign rock and soil onto our eastern shores to make room for the goods and crops they were hauling back home. As the colonies grew and spread, so did the populations of European earthworms. In the twentieth century, however, these slow-moving creatures—

illustration by Yevgenia Nayberg

think again

OnEarth Spring 2014  

Hog Wild, by Ted Genoways

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