I have had a very limited understanding of worms. As a gardener, I think they’re great. As an odd person who thinks about terraforming other planets, I’ve figured that worms should be part of the tool box for making a place more like Earth; and, in fact, they provide a moment of joy in Out of the Dell as someone sees them outside the lone terraformed valley on the alien planet.
But there are different kinds of earthworms. And the jumping earthworms that leave trails of dirt that looks like coffee grounds are not so good for forests, gardens, or the northern United States and Canada. According to this article, the north American glaciers killed off any native earthworms. Later, Europeans brought the European earthworm to the Americas. Now we have the jumping earthworm from Korea and Japan, and they could remake the forests of our continent:
In the absence of worms, North American hardwood forests develop a thick blanket of duff—a mille-feuille of slowly decomposing leaves deposited over the course of years, if not decades. That layer creates a home for insects, amphibians, birds, and native flowers. But when worms show up, they devour the litter within the space of a few years. All the nutrients that have been stored up over time are released in one giant burst, too quickly for most plants to capture. And without cover, the invertebrate population in the soil collapses.
Where millipedes and mites once proliferated, now there are only worms. “If you were to think about the soil food web as the African savanna, it’s like taking out all the animals and just putting in elephants—a ton of elephants,” Dobson says.
With their food and shelter gone, salamanders suffer and nesting birds find themselves dangerously exposed. Plants like trillium, lady’s slipper, and Canada mayflower vanish, too. This may be because the worms disrupt the networks of symbiotic fungus that many native plants depend on, or because worms directly consume the plants’ seeds. Or that native species, accustomed to spongy duff, are ill-prepared to root into the hard soil left behind when the worms have finished eating. It could be all of the above.
Perhaps most worryingly, early studies suggest that worms can sometimes halt the regeneration of trees. Josef Görres, a soil scientist at the University of Vermont, says he often struggles to find a single seedling in invaded portions of New England’s famous maple forests. His theory is that the worms take out all the understory plants, leaving nothing for deer to chew on but the young trees. And that could spell trouble for the region’s prized maple syrup industry. “In 100 years’ time, maybe it’s going to be Aunt Jemima,” he says. “That’s a real bad horror story for people in Vermont.”
As I think about the castings I’ve seen in the park lands across the road from our house, and in remembering how quickly our tree trash decomposes, I’m figuring we’ve got our share of these jumping worms in my neighborhood. I have to admit I’m not feeling too excited about being terraformed.
I have long thought of deer as the Huns of Maryland, devouring not only anything I am foolish enough to plant in the front yard, but the understory of the nearby forest. The forest service has, in fact, begun culling them–not like in Manx Prize, which posits the introduction of belled mountain lions–but with sharp shooters. I don’t walk the dogs in the park during that season.
So, would Planet Builders, Inc. bring jumping worms to transform barren rock worlds and make them hospitable? It sounds very efficient in the short term. On the one hand, if one brought one’s own compost, they might do a great job of getting things started. On the other hand, they might limit what one could plant by inhibiting the development of a proper soil food web. Maybe Planet Builders should just bring the European earthworms.
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