Based on the research of Dr. Peter M. Groffman and colleagues
Perhaps you’ve learned that earthworms are good for the soil. While gardeners may agree with this, ecologists are concerned about the way that earthworms transform their environment. Cary Institute scientists are studying the effects of earthworms on ecosystems.
In the Northeast, most earthworms are actually non-native; they hitchhiked here with settlers in the 1800s. Humans continue to spread earthworms by transporting plants and soil. Fishermen can also accidentally move the animals when they dump unused night crawlers, a popular fish bait.
The importance of leaf litter
And what do these invaders eat? Soil. As they crawl beneath the forest floor, they digest things like decaying roots, fungi, and leaves. In the process, they literally churn the forest floor.
Take a look at the forest floor. The pieces of leaves and twigs that you see underfoot are called leaf litter. This layer of organic debris is important to the health of the forest. It acts as an important barrier, protecting plant roots, retaining moisture, minimizing erosion, and promoting plant regeneration.
Threats to our forests
Scientists believe that earthworms are hurting the health of our forests by eating leaf litter more quickly than it can be replenished. This changes the root structure of plants, affects soil microbes, reduces nutrient levels, and damages habitat for insects and small animals.
This is especially true of jumping worms, an invasive that is new to North America and rapidly spreading. The animals live near the surface of soil, where they rapidly consume leaf litter. You can spot them by the milky white band encircling their body and the coffee-ground-like soil an infestation leaves in its wake.
Casts: A sure sign
Earthworms, like any animal, eat and produce waste. When they burrow, they eat up to 1.5 times their body weight in soil each day. Once digested, they produce and leave behind worm manure. Their shiny brown manure pellets are called worm castings. If you look at the soil surface carefully, you will find worm castings.
Other invasive species
Earthworms are not the only invaders our forests face. Cary Institute researchers are actively investigating other threats, such as beech bark disease, spongy moths, and an aphid-like pest called the hemlock woolly adelgid.
Understanding their impact will help us manage and protect our forested areas. This information is critical in the face of combined pressure from new invasive species and climate change.