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

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...

, 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 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''; plural 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 nam ...

'' in twelve

families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideal ...

are reported from the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

and

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

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

lumbricid The Lumbricidae are a family of earthworms. About 33 lumbricid species have become naturalized around the world, but the bulk of the species are in the Holarctic region: from Canada (e.g. ''Bimastos lawrenceae'' on Vancouver Island) and the Uni ...

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) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

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'' 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 substance used to attract and catch fish, e.g. on a fishing hook. Bait items are both selected from and placed within the environment to achieve enhanced prey capture success. Traditionally, fishing baits are natural fish foo ...

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'' 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

At this point 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, but may also be caught from stocked bodies of water such as ponds, canals, park wetlands and reservoirs. Fishing techniques inclu ...

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, recr ...

, 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 cen ...

'') and

honeysuckle Honeysuckles are arching shrubs or twining vines in the genus ''Lonicera'' () of the family Caprifoliaceae, native to northern latitudes in North America and Eurasia. Approximately 180 species of honeysuckle have been identified in both conti ...

(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