Earthworms are good for soil
Most of the earthworms found in Frederick County soils were brought over from Europe and Asia, particularly the large night crawlers often used for fish bait.
Earthworms are considered beneficial for agricultural land and gardens but not so good for forests. In an agricultural setting, the presence of earthworms enhances water absorption, root growth, soil fertility and crop yields. Worms accomplish this by digging burrows in the ground. These burrows help aerate the soil, which increases water absorption and provides more spaces for roots to expand.
Earthworms are also efficient at decomposing dead organic matter and converting it to a source that is readily taken up by fast-growing agricultural crops like corn, soybeans, vegetables and flowers.
These worms also have a digestive gland that makes what they excrete more basic in pH, thereby raising the alkalinity of soils. This also tends to favor cultivated plants. Earthworms also help to reduce global climate change by decomposing organic material without creating much carbon dioxide or methane gas.
Although good for crops, the activity of earthworms is not beneficial for most forest lands, especially in the Northern states. In those areas that were impacted by glaciers, most of the earthworms were eliminated. Worms were reintroduced to these areas soon after European settlement occurred.
In the absence of worms, these areas were dependent on mushrooms and other fungi to decompose organic matter, and this process took much longer as a result. As such, the forests had a large accumulation of organic matter on the ground and much of this matter was acidic.
Once worms were introduced, these creatures significantly sped up the decomposition of this "duff" layer so that what might take five years for fungi to decompose took a single season for the worms. The rapid removal of this duff layer exposes soil; erosion and surface runoff are increased and fine roots of fragile forest plants, like wildflowers and herbs, are exposed and causing the demise of the plant.
Earthworms also raise the pH of forest soils and quickly decompose nutrients that harm acid-loving plants like many trees. This also causes leaching of nutrients into the groundwater. This removal of forest duff also affects the many insects, amphibians, reptiles, birds and mammals that live on the forest floor.
These nonnative worms, like other foreign insects, diseases and plants, have created changes that our forests have had to adjust to.
Nature Notes articles FCFCDB member
Nature Notes for 8/12/2012