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Most people do not realize that all earthworms found in these forests are non-natives, the native earthworm species having been eliminated by glaciers during the last ice age that ended approximately 16,000 years ago.

While earthworms have the reputation of being beneficial in gardens and farms, their impact in forest ecosystems that have developed over thousands of years without earthworms is of concern. Studies have demonstrated the ways in which non-native earthworms greatly affect these forests by modifying the forest floor, including altering how nutrients are cycled in the soil and changing the conditions to which plants, animals, and microbes have become adapted.

In the early 1990s, a group of ecologists began studying the effects of urbanization on forests by comparing forests along an urban-rural gradient extending 130 km from New York City to western Connecticut.

One quite unexpected discovery was the much greater abundance of non-native earthworms at the urban end of this gradient.

Dr. Faith Kostel-Hughes, Shonda Gaylord, and Megan Skrip

Dr. Kostel-Hughes and her students have begun conducting studies to follow-up on this earlier research on the distribution of earthworms along this gradient. They are also conducting studies to investigate some of the impacts of the changes wrought by these earthworms on other organisms, including invertebrates that live in leaf litter and both native and non-native plant species.