You've probably heard that earthworms are good for the soil and can help create rich dirt for healthy gardens. And while earthworms may seem like harmless creatures, scientists are finding that certain earthworm species can be deadly to trees and forests.

Earthworms help crops by adding air and oxygen to the soil and providing it with nutrients, but in another ecosystem - the forest - they can weaken root systems and hurt trees.

Researchers in the Great Lakes region, which has no native earthworm species, are busy examining worms for possible destructive properties and reaching out to residents to encouraging them not to dump their fishing bait in the woods. The goal is to stop the spread of invasive and destructive worms.

"Worms literally eat the rooting zone out from underneath the plants, removing habitat for seeds, young plants, even small animals." - NewsHour Science Correspondent Miles O’Brien

"The earthworm really changes the structure, the chemistry, the nutrient dynamics and the habitat for all the organisms that live in that soil." - Cindy Hale, ecologist, Natural Resources Research Institute

1. What do you know about earthworms? What is their role in an ecosystem?

2. What is the difference between a native species and a non-native species?

3. Name a plant or animal species that's native to the the area where you live.

1. If you were a gardener, would you want earthworms living in your soil? Why or why not? What you lived in a forest, would you want earthworms in your garden?

2. What is the definition of an invasive species?

3. Can you think of examples of how non-native, invasive species have threatened other ecosystems?

4. How do you think researchers should inform the public about the earthworm problem?