In glaciated northern plains, few earthworms existed prior to European settlement.

Old World earthworms from soil in potted plants quickly invaded the New World, forever changing the delicate balance under the soil.

Invasive earthworms may speed up nutrient cycles: moving detritus down into the soil, where organic molecules can leach down, out of reach of trees.

Such disturbance may aid the spread of Old World invasive plants such as Common Buckthorn (Rhamnus cathartica) and Garlic Mustard (Alliaria petiolata).