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Earthworms Contributing to Decline in New Hampshire Wildlife


Invasive earthworms are putting New Hampshire wildlife and ecosystems at risk due to their absorption of heavy metals. 

Earthworms are considered an invasive species in New Hampshire where the forests have developed without them since the last Ice Age drove them further south.

In recent times exotic worms from Asia and Europe have been reintroduced through fishing, waste management projects, and from farmers to help with their gardens.

In a recent study by Dartmouth College and the University of Vermont, researchers analyzed nine different forests in both Vermont and New Hampshire. They found the exotic earthworms had spread rapidly through all nine sites and may be the cause behind the sudden decline in wildlife populations.

Soil samples normally contain large amounts of heavy metal contamination from humans burning coal and lead-based gasoline. The worms have absorbed those metals, specifically the lead and mercury found in them, to toxic levels. These toxic chemicals were then transferred to wildlife who feasted upon the worms, eventually killing them.

Dr. Justin Richardson, one of the lead authors of the research stated, “Our results suggest that exotic earthworms could be responsible for the high levels of toxic metals in ground foraging animals such as birds, amphibians, and even mammals across New England. Our research highlights two important messages: Earthworms are not native in the forests of New England and they may negatively impact what forest soils do well; retaining pollutant trace metals from food webs.”

Earthworms aren’t just affecting New Hampshire wildlife either, but in numerous northern states where the worms have been introduced to the soil.

Earthworms that had made their way into the hardwood forests of Minnesota’s Chippewa National Forest and Wisconsin’s Cehquamegon-Nicolet National Forest have destroyed the natural leaf flooring on the forest floor.

The ovenbird found in these forest is a ground nesting bird that used the once thick layer of leaves to build and camouflage their nests. The covering was also used by numerous litter-dwelling insects that birds and other wildlife in the area rely on for food.

It is not too late to reverse these worms from moving to and destroying any more than they have.

Minnesota’s Department of Natural Resources states on their website, “Without humans moving them around, earthworms move slowly, less than a half mile over 100 years. If we stop introducing them we can retain earthworm free areas for a long time.”

Most of the northern states have made it illegal for worms to be added to the soil for gardening purposes, and are fining fisherman who dump their unused bait onto the ground.

They are also asking anyone living in these states to report any worms found while landscaping or that have surfaced while outdoors to the Great Lakes Worm Watch.

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Earthworms Contributing to Decline in New Hampshire Wildlife