Invasive earthworms of North America

Invasive species of earthworms from the suborder Lumbricina have been expanding their range in North America. Earthworms are considered one of the most abundant macroinvertebrates in the soil of ecosystems in temperate and tropical climates. There are around 3,000 species known worldwide. They are considered keystone species in their native habitats of Asia and Europe because, as detritivores, they alter many different variables of their ecosystem. Their introduction to North America has had marked effects on the nutrient cycles and soil profiles in temperate forests. These earthworms increase the cycling and leaching of nutrients by breaking up decaying organic matter and spreading it into the soil. This thins out the soil rapidly because earthworms do not require a mate to reproduce, allowing them to spread fast. Since plants native to these northern forests are evolutionarily adapted to the presence of thick layers of decaying organic matter, the introduction of worms can lead to a loss of biodiversity as young plants face less nutrient-rich conditions. Some species of trees and other plants may be incapable of surviving such changes in available nutrients. This change in the plant diversity in turn affects other organisms and often leads to increased invasions of other exotic species as well as overall forest decline. They are considered one of the most invasive animals in the Midwestern United States along with feral swine.