Earthworms An earthworm is a soil-dwelling terrestrial animal, terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (biology), class (or subclass (biology), subclass, depending on ...

are

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

throughout the world. Of a total of about 6,000 species of

earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...

, 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

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

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
''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 An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived ther ...

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

North America

Approximately 182 earthworm ''

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

'' in twelve

families Family (from ) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictability, structure, and safety as ...

are reported from the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, of which sixty (about 33%) are introduced. Only two

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

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

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

s 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 ''Lumbricus terrestris'' is a large, reddish worm species thought to be native to Western Europe, now widely distributed around the world (along with several other Lumbricidae, lumbricids). In some areas where it is an introduced species, some ...

'' and '' L. rubellus'' and the Alabama (technically Asian) jumper, '' Amynthas agrestis'', can be eaten by adult

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...

s, 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 Fishing bait is any bait (luring substance), luring substance used specifically to attract and fishing, catch fish, typically when angling with a fish hook, hook and fishing line, line. There are generally two types of baits used in angling: '' ...

United Kingdom

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.

East Asia

In Taiwan, ''

Pontoscolex corethrurus ''Pontoscolex corethrurus'' is an earthworm in the genus ''Pontoscolex''. It has a circumtropical distribution, although it originates in the Neotropics, probably in the Guiana Plateau. Description The worms are unpigmented and have around 2 ...

'' is known invasive with evidence of it displacing native worms. ''

Eudrilus eugeniae ''Eudrilus eugeniae'', also called the "African nightcrawler", is an earthworm species native to tropical west Africa and now widespread in warm regions under vermicompost; it is an excellent source of protein and has great pharmaceutical potent ...

'' has potential to do the same. For vermicompost, the native or naturalized ''

Perionyx excavatus ''Perionyx excavatus'' is a commercially produced earthworm. Popular names for this species include composting worms, blues, or Indian blues. This species is marketed for its ability to create fine worm castings quickly. It has recently become m ...

'' is recommended.

Control

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. One simple measure is to reduce the number of worms released during

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment (Freshwater ecosystem, freshwater or Marine ecosystem, marine), but may also be caught from Fish stocking, stocked Body of water, ...

practices. The

Minnesota Department of Natural Resources The Minnesota Department of Natural Resources, or Minnesota DNR, is the agency of the U.S. state of Minnesota charged with conserving and managing the state's natural resources. The agency maintains areas such as state parks, state forests, rec ...

, in cooperation with local groups, has launched a public education campaign using posters in bait shops and other outreach efforts. 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. 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. 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 ''Rhamnus cathartica'', the European buckthorn, common buckthorn, purging buckthorn, or just buckthorn, is a species of small tree in the flowering plant family Rhamnaceae. It is native to Europe, northwest Africa and western Asia, from the cent ...

'') and

honeysuckle Honeysuckles are arching shrubs or Vine#Twining vines, twining vines in the genus ''Lonicera'' () of the family Caprifoliaceae. The genus includes 158 species native to northern latitudes in North America, Eurasia, and North Africa. Widely kno ...

(e.g., ''Lonicera'' × ''bella''), which produce leaf litter favored by worms. 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. People with invasive worms on their property are advised not to move plants or soil from their property.

Australia

North America

United Kingdom

East Asia

Control

References

Further reading