Earthworms as invasive species

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. The total native species numbers are predicted to exceed 1,000.Blakemore, Rob, [http://www.annelida.net/earthworm/Australasian%20Earthworms/Australian%20Exotics.pdf Diversity of exotic earthworms in Australia - a status report.] Transactions of the Royal Zoological Society of New South Wales, 1999 "Approximately 350 native species in about 30 genera are currently described for Australia, but an estimate of total number is about three times as large (Blakemore 1997a)."

Introduced species are commonly found in agricultural environments along with persistent natives. 66 exotic species are known by 1999, most of which have been introduced accidentally.

{{Main|Invasive earthworms of North America}}

Approximately 182 earthworm taxa in twelve families are reported from the United States and Canada, of which sixty (about 33%) are introduced.Blakemore, R. 2006 [http://www.annelida.net/earthworm/American%20Earthworms.pdf American earthworms (Oligochaeta) from north of the Rio Grande.] 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 L. rubellus and the Alabama (technically Asian) 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.Crawling to Oblivion, Scientific American, 300, 3 (March 2009), p. 22

Currently there is no economically feasible method for controlling invasive earthworms in forests.{{Cite web | title = Great Lakes Worm Watch - What can I do? | publisher = University of Minnesota | year = 2011 | url = http://greatlakeswormwatch.org/team/action.html | accessdate = 31 January 2019}} 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,Blakemore, R.J. 2008 [http://www.annelida.net/earthworm/Britain%20&%20Ireland.pdf http://www.annelida.net/earthworm/Britain%20&%20Ireland.pdf] 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.

In Taiwan, Pontoscolex corethrurus is known invasive with evidence of it displacing native worms. Eudrilus eugeniae has potential to do the same.{{cite web |trans-title=Earthworms aren't all good; Exotic earthworms are mix-kept en masse, causing ecological shock |title=並非蚯蚓就是好 外來蚯蚓大量混養 引發生態衝擊 |url=https://www.newsmarket.com.tw/blog/89773/ |website=上下游News&Market |access-date=22 May 2022 |language=zh-TW |date=22 November 2016}} For vermicompost, the native or naturalized Perionyx excavatus is recommended.{{cite web |title=印度藍蚯蚓：你不知道養殖上有多好用的本土種——太平二號與牠們的產地（三） |url=https://pansci.asia/archives/109587 |website=PanSci 泛科學 |language=zh-TW}}

There is no known way to remove the earthworms from the soil, so proposals have focused on ways to slow their spread.Lee E. Frelich, Cindy M. Hale, Stefan Scheu, Andrew R. Holdsworth, Liam Heneghan, Patrick J. Bohlen and Peter B. Reich. 2006. Earthworm invasion into previously earthworm-free temperate and boreal forests. Biological Invasions 8: 1235–245. {{doi|10.1007/s10530-006-9019-3}} One simple measure is to reduce the number of worms released during fishing practices. The Minnesota Department of Natural Resources, in cooperation with local groups, has launched a public education campaign using posters in bait shops and other outreach efforts.{{Cite book|url = http://www.fs.fed.us/global/iitf/pubs/ja_iitf_2006_Callaham001.pdf|last1 = Callaham|first1 = Mac A. Jr.|date = 1 September 2006|journal = Biol. Invasions|doi = 10.1007/978-1-4020-5429-7_11|last2 = González|first2 = Grizelle|author-link2=Grizelle González|last3 = Hale|first3 = Cynthia M.|last4 = Heneghan|first4 = Liam|last5 = Lachnicht|first5 = Sharon L.|last6 = Zou|first6 = Xiaoming| title=Biological Invasions Belowground: Earthworms as Invasive Species | chapter=Policy and management responses to earthworm invasions in North America |volume = 8|pages = 1317–1329|isbn = 978-1-4020-5428-0}}

The movement of dirt from one location to the other could also be regulated so that dirt from areas where earthworms are common is not moved into forests without the invasive species.Nico Eisenhauer, Stephan Partsch, Dennis Parkinson and Stefan Scheu. 2007. Invasion of a deciduous forest by earthworms: changes in soil chemistry, microflora, microarthropds, and vegetation. Soil Biology and Biochemistry 39: 1099-110.{{doi|10.1016/j.soilbio.2006.12.019}} To prevent the spread of invasive earthworms, it is recommended that people should only purchase compost or mulch that has been heated to appropriate temperatures and duration following protocols that reduce pathogens and kill the earthworm cocoons, or eggs.{{Cite journal|last1=F.|first1=Hendrix, Paul|last2=J.|first2=Bohlen, Patrick|date=2002-09-01|title=Exotic Earthworm Invasions in North America: Ecological and Policy ImplicationsExpanding global commerce may be increasing the likelihood of exotic earthworm invasions, which could have negative implications for soil processes, other animal and plant species, and importation of certain pathogens|journal=BioScience|language=en|volume=52|issue=9|pages=801|doi=10.1641/0006-3568(2002)052[0801:EEIINA]2.0.CO;2|issn=0006-3568|doi-access=free}}

In areas that have already been colonized, the number of worms can be reduced by removal of introduced shrubs such as common buckthorn (Rhamnus cathartica) and honeysuckle (e.g., Lonicera × bella), which produce leaf litter favored by worms.{{Cite journal|title = Removal of invasive shrubs reduces exotic earthworm populations|last1 = Madritch|first1 = Michael D.|date = 13 May 2008|journal = Biol. Invasions|doi = 10.1007/s10530-008-9281-7|last2 = Lindroth|first2 = Richard L.|volume = 11|issue = 3|pages = 663–671| s2cid=26504134 }} This may help mitigate negative impacts on the ecosystem.

Mustard pours can be used to survey for invasive worms at a site. A mustard pour can be created by mixing a gallon of water with one third cup of ground yellow mustard seed. Pouring the solution slowly over the soil will drive worms to the soil's surface without harming the plants.{{Cite web |url=http://nrri.d.umn.edu/worms/research/methods_worms.html |title=Earthworm Sampling Methods |website=Great Lakes Worm Watch |publisher=University of Minnesota Duluth |access-date=January 30, 2020}} People with invasive worms on their property are advised not to move plants or soil from their property.

{{Reflist|35em}}

• 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.

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