Although native earthworms became extinct from most of North America during the ice age 10,000 years ago, earthworm species from southern Europe, which were brought to North America by European settlers centuries ago, are now showing up on North America forest floors, according to recent reports.
These slimy invertebrates play important roles in the soil food web, breaking down and consuming dead organic matter, which helps fertilize the soil. Earthworms also excrete waste in the form of castings, which improves water retention in soil.
However, earthworms may also increase greenhouse gas emissions by helping organic plant residues mix in the soil, which may increase decomposition, resulting in the release of carbon dioxide into the atmosphere. In addition, the earthworms increase the activity of nitrous oxide-producing microbes, allowing greenhouse gases in the soil to leak out into the environment.
"Earthworms are yet another factor that can affect the carbon balance," Werner Kurz, a researcher with the Canadian Forest Service in Victoria, British Columbia, told the National Post.
Erin Cameron, an environmental scientist at Saint Mary's University in Halifax, Nova Scotia, who studies the earthworms in the Boreal Forest, a snow forest that covers most of inland Canada in North America, found that 99.8% of the earthworms in Alberta, Canada, are part of a species that consumes leaf litter but doesn't burrow into the soil. Earthworms feast on the layer of leaves on the forest floor, releasing carbon in the process, according to the National Post.
According to scientists, earthworms will grow in population worldwide as parts of North American forests continue to be invaded by them.
That being said, 76% of manmade greenhouse gas emissions are carbon dioxide, while 16 percent of manmade greenhouse gas emissions are methane emissions, which come mostly from the agriculture industry, according to the Center for Climate and Energy Solutions.