ST. PAUL, Minn. - Autumn is here and the floors of Minnesota forests are getting blanketed with leaves.

By spring, most of them will be gone thanks to European Earthworms. New research from the University of Minnesota shows that these non-native creatures are changing our forests.

"The European Earthworm invasion has a very large negative impact on the diversity of our native plant species in North America. The grasses are favored, so grasses do better after the earthworms invade. Things like trilliums, orchids and violets don't do as well." said Lee Frelich, Director of UMN Forestry Ecology.

In addition, researchers say that these worms facilitate in the invasion of garlic mustard and Buckthorn by changing our soils.

"We had many years worth of leaf litter. It was like a mattress, very spongy. It would be 20, 30, or 40 years of leaf liter that decayed very slowly. Earthworms eat dead leaves, that's what they do for a living. So that forest floor is gone and we now have bare mineral soil." said Frelich.

Native plants thrive in leafy soils. Back in 1840's when European settlers arrived in Minnesota they also brought the worms.

"We really don't know how to remove earthworms without poisoning them; but the problem is that poisons all sorts of other things that should be there." said Frelich.

Research will continue at the U of M to see if and how these European worms can be removed from our soils and allow our forests to thrive. For more about invasive earthworms and what you can do to contain the crawlers, click here.