Earthworms as invasive species
Earthworms are invasive species throughout the world. Of a total of about 6,000 species of earthworm, about 120 species are widely distributed around the globe. These are the peregrine or cosmopolitan earthworms. Some of these are invasive species in many regions.
Australia has 650 known species of native earthworm that survive in both rich and in nutrient-poor conditions where they may be sensitive to changes in the environment. Introduced species are commonly found in agricultural environments along with persistent natives. Most of the 75 or so exotics have been introduced accidentally. The total species numbers are predicted to exceed 2,000.
A total of approximately 182 earthworm taxa in 12 families are reported from the United States and Canada, of which 60 (about 33%) are introduced. Only two genera of lumbricid earthworms are indigenous to North America while introduced genera have spread to areas without any native species, especially in the north where forest ecosystems rely on a large amount of undecayed leaf matter. When worms decompose that leaf layer, the ecology may shift making the habitat unsurvivable for certain species of trees, ferns and herbs. Larger earthworms such as the nightcrawler Lumbricus terrestris and the Alabama jumper, Amynthas agrestis, can be eaten by adult salamanders, which is beneficial for their populations, but they are too large for juvenile salamanders to consume, which leads to a net loss in salamander population.
Currently there is no economically feasible method for controlling invasive earthworms in forests. Earthworms normally spread slowly, but can be quickly introduced by human activities such as construction earthmoving, plantings, and the release of worms used as fishing bait.
For the 69-70 known species, a recent threat to earthworm populations in the UK is the New Zealand flatworm (Arthurdendyus triangulatus), which feeds upon earthworms but has no local natural predator itself. Sightings of the New Zealand flatworm have been mainly localised, but it has spread extensively since its introduction in 1960 through contaminated soil and plant pots. Any sightings of the flatworm should be reported to the Scottish Crop Research Institute, which is monitoring its spread.
- Cosmopolitan Earthworms
- Plisko, J.D. 2010. Megadrile earthworm taxa introduced to South African soils (Oligochaeta: Acanthodrilidae, Eudrilidae, Glossoscolecidae, Lumbricidae, Megascolecidae, Ocnerodrilidae). African Invertebrates 51 (2): 289-312. Africaninvertebrates.org.za
- Blakemore, Rob, Diversity of exotic earthworms in Australia - a status report. Transactions of the Royal Zoological Society of New South Wales, 1999
- Blakemore, R. 2006 American earthworms (Oligochaeta) from north of the Rio Grande.
- Crawling to Oblivion, Scientific American, 300, 3 (March 2009), p. 22
- "Great Lakes Worm Watch - What can I do?". University of Minnesota. 2011. Retrieved 21 April 2012.
- Blakemore, R.J. 2008 http://www.annelida.net/earthworm/Britain%20&%20Ireland.pdf
- Blakemore, R. J. American Earthworms from North of the Rio Grande- a Species Checklist. Rep. Yokohama, Japan: YNU, 2006.
- Campbell, Neil A., and Jane B. Reece. Biology. San Francisco: Pearson Benjamin Cummings, 2009.
- Bohlen, Patrick J., Derek M. Pelletier, Peter M. Groffman, Timothy J. Fahey, and Melany C. Fisk. "Influence of earthworm invasion on redistribution and retention of soil carbon and nitrogen in northern temperate forests." Ecosystems 7 (2004): 13-27.
- Eisenhauer, Nico, Stephan Partsch, Dennis Parkinson, and Stefan Scheu. "Invasion of a deciduous forest by earthworms: changes in soil chemistry, microflora, microarthropds, and vegetation." Soil Biology and Biochemistry 39 (2007): 1099-110.
- Frelich, Lee E., Cindy M. Hale, and Stefan Scheu. "Earthworm invasion into previously earthworm-free temperate and boreal forests." Biological Invasions 8 (2006): 1235-245. Print.
- Hendrix, P. F., G. H. Baker, and M. A. Callaham Jr. "Invasion of exotic earthworms into ecosystems inhabited by native earthworms." Biological Invasions 8 (2006): 1287-300.
- Szlavecz, Katalin, Sarah A. Placella, and Richard V. Pouyat. "Invasive earthworm species and nitrogen cycling in remnant forest patches." Applied Soil Ecology 32 (2006): 54-62.