The worms are not like the other night crawlers. They are not from around here. When held they thrash and jump. They do not live deeply, but they are very good at sucking down their food and passing it out in a gravelly residue.
They are, according to the standards by which biologists judge worms, aggressive.
To experts they are Amynthas agrestis, but they have many other names: the crazy-snake worm, the Asian jumping worm (betraying their native roots) and the Georgia jumper or Jersey wiggler (revealing their newer, East Coast digs). The jumping worm has been spotted devouring the leaf litter in the Smoky Mountains and denuding the forest floor beneath the hardwoods that grow near the Great Lakes. Most recently, in August and to the concern of agricultural officials, the worms were discovered in Oregon.
You may be wondering how, on earth, a worm could cause such hullabaloo. North America has had foreign worms in its soil since the 1600s, when they crossed the Atlantic in European ships and root balls in cargo holds. After all, aren’t worms supposed to be one of the little things that rule the garden, their slick bodies like tills that churn the soil into a rich humus?
“Earthworms are the kind of organisms we call ecosystem engineers. They change the physical and chemical properties of the ecosystem as they dig and feed,” University of Wisconsin-Madison zoologist Monica Turner said in a statement. “But nobody really understood if these Asian worms would have the same effect as the European worms we have had here for many years.”
The problem with the Asian jumping worm seems to be, a study conducted by Turner and her colleagues confirms, that the animal is too good at half of its job — eating — and not nearly as helpful on the burrowing front.
The UW Madison researchers added worms to a plot of forest in a 4-month controlled outdoor experiment, and also studied field sites in Wisconsin where the worms had been discovered in 2013. In both cases, the animals decreased the nutrient-rich leaf litter 84 to 95 percent by mass, according to the paper published recently in the journal Biological Invasions.
The soil that remained was “bare and clumpy,” Turner said. At the same time, inorganic nutrients left behind by the worms — nitrogen and phosphorus, on which plants feed — spiked in the top two inches of dirt. In other words, as the nonnative worms stripped the leaf litter, nutrients clumped up at the surface of the soil. There, the inorganic elements are inaccessible to hungry plant roots.
Turner compared the difference between the Asian jumping worms and other worms as the difference between a quick- and slow-release fertilizer. Some plants are simply not equipped to ingest a sudden food flood. The researchers worry, too, that as the nutrients concentrate at the soil’s very top, strong rains could wash nitrates and other dissolvable minerals away.
What contains the damage these worms can do is that, on their own, they cannot travel long distances — no more than 30 feet a day. However, like worms of yore, they may be transported in cargo or the root balls of garden plants, or when sold for fishing bait.
In Oregon, officials with the Department of Agriculture have asked residents to capture any jumping worms spotted. Unlike other earthworms, these worms have a pale band near their midsection that is not raised. And, of course, they wriggle with unusual vigor.