Invasion of the exotic earthworms!
Dispatches from the Field > Invasive earthworms
You may know this worm already, although when the Asian Jumping Worm (Amynthas agrestis) is sold for bait or composting as the Alabama Jumper or Georgia Jumper, there is no mention of the destruction it can bring to forests.
Composting ads boast that the worm can eat and process more than its body weight in organic matter (vegetable scraps, leaves, lawn trimmings, etc.) each day. That same tenacious appetite means that when people release their bait (or their bait escapes) and the worms make their way to the forest, they consume massive amounts of leaf litter. If you were a leaf-litter-feeder such as a millipede, fly larvae, or springtail, this would be a big problem because your food source would be gone! It would also be bad if you were a creature that ate these invertebrates. In some areas on the western side of the Smokies, the Jumping Worm population is so high there is almost no leaf litter left. Without this food, native animals are disappearing, and the nutrients from decaying plants aren’t there to build new soil!
This brings us to important research going on this summer: Anita Juen and Daniela Straube, two scientists from the University of Innsbruck in Austria, are beginning a three year study to analyze what these worms are doing to the park’s food web—in this case, if predators change their diet to eat the invasive earthworms. The researchers received funding from the Austrian Science Fund. They collaborate with scientists at the University of Georgia in Athens and the Skidaway Institute of Oceanography in Savannah.
Researchers look for the worm along roads, picnic areas, and parking areas near trailheads, where people and disturbed areas come together. They collect leaf litter and soil samples from all of the study sites and carefully sift through huge bagfuls with the help of volunteers. Archeologists check the soil, as well, to ensure the research doesn’t disturb artifacts. The researchers pick out all of the living things in the soil, including predators, leaf-litter feeders (also called detritivores), and root feeders for a full census of who lives in the soil.
So far, the researchers have found the invasive Jumping Worm at about half their study sites in the Smoky Mountains, which allows them to compare types and numbers of prey species in invaded and non-invaded sites. This will tell them how much of an effect the Jumping Worm has!
In all types of ecosystems—from the soil to the treetops and the seas—we’re finding more invasive, non-native species, and usually we don’t know how they will play a role in the overall food web. Some studies have found huge impacts. In a study in Spain, researchers discovered that native species of tadpoles can’t sense, and therefore can’t escape from, non-native turtles that people introduced. Over time this means that the introduced turtles could eat their fill of tadpoles, depleting the tadpole population (and therefore the frog population, as well), leading to more swarms of insects and a loss of a food source for native turtles. Will something like this happen in the Smokies with the invasive Jumping Worm? We don’t know—but check back for more information.
Click for photos of citizen scientists volunteering for this and other projects (coming soon).
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Did You Know?
An experimental program to reintroduce elk to the park was begun in 2001. Elk once roamed the Smokies, but were eliminated from the region in the mid 1800s by over-hunting and loss of habitat. Other animals successfully reintroduced to the park include river otters and barn owls. More...