Invasive earthworms of North America

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Lumbricus herculeus and Lumbricus terrestris, widely spread invasive earthworms native to Europe. Lumbricus herculeus (left) and Lumbricus terrestris (right).png
Lumbricus herculeus and Lumbricus terrestris, widely spread invasive earthworms native to Europe.

Invasive species of earthworms from the suborder Lumbricina have been expanding their range in North America. [1] Earthworms are considered one of the most abundant macroinvertebrates in the soil of ecosystems in temperate and tropical climates. [2] There are around 3,000 species known worldwide. [2] They are considered keystone species in their native habitats of Asia and Europe because, as detritivores, they alter many different variables of their ecosystem. [3] 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. [4] 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. [5] 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. [3] [6] They are considered one of the most invasive animals in the Midwestern United States along with feral swine. [7]

Contents

Earthworms and range shifts

Earthworms are shifting their ranges northwards into forests between 45° and 69° latitude in North America that have lacked native earthworms since the last ice age. [3] Of the 182 taxa of earthworms found in the United States and Canada, 60 (33%) are introduced species, these earthworm species are primarily from Europe and Asia. [5] [8] Among these, Lumbricus terrestris , L. rubellus, L. friendi, Amynthas agrestis , and Dendrobaena octaedra have been studied for their ability to invade previously uninhabited locations and disturb the local ecosystems and nutrient cycles. [3] [8] By redistributing nutrients, mixing soil layers, and creating pores in the soil, they can affect the characteristics of the soil important to the rest of the ecosystem. Earthworms break up decomposing matter on the surface of the soil and carry or mix it into the surrounding soil, often carrying some of the nutrients deeper into the soil, where saplings and other young plants have trouble reaching them. [9]

Influence on nutrient cycles and soil profiles

When organisms die and plants undergo senescence, their detritus fall to the forest floor, where they begin decomposing into their constituent nutrients. [10] In the absence of efficient detritivores such as earthworms, a thick layer of such organic matter accumulates. Most northern forests in North America lack native earthworms, which were largely wiped out when the ice sheets of the Wisconsin glaciation scoured much of the continent down to the bedrock. A deep detritus layer is thus characteristic of the native ecosystem of the region, and many native plants have evolved to rely on it. [5] As it slowly decomposes, it supplies nutrients, particularly potassium, phosphorus, and nitrogen, that are necessary for the production of cellular components such as carbohydrates, nucleic acids, and proteins; these nutrients are often a limiting factor in growth and maturation. [5] This provides for the growth of trees, ferns, and smaller ground plants.

When earthworms are introduced into areas where they previously did not reside, the earthworms break up the organic layer. They do this physically by burrowing, consuming and redistributing leaf litter, and leaving behind castings in the soil. [11] They often mix the nutrients into the soil, out of the reach of all but the deeper tree roots. Nutrients may then be leached and lost from the ecosystem entirely. Overall effects include a decrease in the thickness of the organic layer, increased mineralization, increased bulk density, spreading of the organic matter and humus, and increased rate of decomposition. [1] [3] [9] These environmental alterations (drier, brighter, less nutrient-rich soil) create changes to the ecosystem. Podzol soils lose their classic banded appearance when earthworms obliterate their eluvial (A2, Ae, or E) horizons. [12] [13]

Effects

Invasive earthworms have caused a decrease in diversity, seedling populations, forest floor organic matter volume, and overall habitat quality. In addition, there is often an increase in invasive species and a decreased diversity of non-plant organisms. Some species that provide important biological niches to the ecosystem may be eradicated.

Effects on plants

Because earthworms take away valuable nutrients needed by plants, [3] young plants may be unable to grow without the surface nitrogen source provided by the layer of detritus. [9] Since young plants do not have the deep root systems that older trees have, they often cannot obtain enough nutrients to survive. [1] Thus, few saplings or under-canopy plants grow to full maturity and generally only the larger trees with extensive root systems survive. The addition of earthworms to an environment has been shown to decrease mycorrhizal associations with roots. This adds to the problem of finding available nutrients for plants. [3] Many different species of earthworms throughout Northern Minnesota and Wisconsin have been connected with the reduction of native plants. [14] Specifically, trees like poplar, birch, and maple are disfavored by the change in habitat, as are many forest herbs like Aralia , Viola, and Botrychium . These plants are strongly negatively effected by the activity of invading earthworms. [15] When a decrease in overall ground cover and canopy vegetation occurs, the few plants remaining are often eaten shortly after germination. [5]

Generally, with the addition of earthworms to a forest, a decrease in diversity is observed, and often other exotic species follow that can survive the nutrient-diminished environment better than the natives. It has been observed that the presence of earthworms has a strong positive effect on the biomass of invasive plant species. [16] For example, in newly invaded forests buckthorn and garlic mustard, both invasive species, increase notably in population density. [3] [6]

Effects on animals

When invasive earthworms cause a decrease in overall ground cover and canopy vegetation, food for other organisms becomes scarce. [5] As a result, some organisms are forced to leave the areas. With decreased ground-level vegetation, many terrestrial organisms like insects, small mammals, and other vertebrates must compete for fewer resources, leading to decreased diversity and population. [6] In addition, the native species of worms may be unable to compete with the introduced species because the native ones are not well adapted to the new conditions of the forest soil. [10] For example, Millipedes in particular are competing for resources with Asian earthworms in the southern Appalachian Mountains. [17] Moreover, the decrease in plant biomass due to species richness affects earthworms is directly related to trophic levels. The lower trophic levels are affected less than the higher trophic levels. [18]

Origins

Most of the invasive earthworms are European or Asian and came over in soil during the 18th century as Europeans began settling the North American continent. The worms were originally transferred through the horticultural trade, probably in the soil bulbs of European plants carried to the Americas. Some earthworms have been brought over to be used as bait for fishing and escaped or got released. For example, at least one species of earthworm was introduced in Alaska as bait for anglers. [19] The lack of competition from native earthworms allowed the invaders to flourish. [20] Now recreational practices and construction methods are the primary mode of transportation for the earthworms. [3] Their movement in the soil is slow, but with human transportation, they can migrate much faster. In addition, many are moved physically in soil through construction practices in dirt loads. [1]

Certain characteristics of soil habitat may affect the ability of the earthworms to invade an environment. High salinity and sandy soils have greater resistance to earthworm spread. [3] Low pH and the presence of plant matter with a high carbon-to-nitrogen ratio (C:N) may promote resistance; conversely, high pH and low C:N ratios appear to confer greater susceptibility.

Asian earthworms

More recently than the invasion of European earthworms, Asian earthworms have been introduced by human activities. [21] Particularly of the genera Amynthas and Metaphire . [22] These earthworms have a variety of nicknames due to their characteristic thrashing behavior, including "Asian jumping worms", [23] "Alabama jumpers", [24] "crazy worms", and "snake worms". [25] The effects of invasive Asian earthworm species are much less documented than those of European lumbricid earthworms, but there is greater concern over the potential effects of jumping worms on soil structure and chemistry, nutrient cycling, forest regeneration, and animal and plant communities. [22] Evidence shows that Asian earthworms grow more rapidly, [26] reproduce more quickly, and have greater flexibility in their diet than European species. [27] They can also exist at higher densities than European earthworm species. These characteristics may allow jumping worms to outcompete their European earthworm competitors. These traits mean that jumping worms can consume organic matter more rapidly, stripping the forest floor of organic matter and temporarily flooding the system with nutrients. Northeastern forests evolved under the slow decomposition and release of nutrients, and it is still unclear how forests are responding to the rapid breakdown of organic material.

Prevention

This section is an excerpt from Earthworms as invasive species § Control.[ edit ]

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. [28] 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. [29]

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. [30] [29] 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. [31]

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. [32] This may help mitigate negative impacts on the ecosystem.

Removal

A demonstration on the method of worm collecting called worm grunting.

One way invasive earthworms can be removed from the environment is worm grunting. Worm grunting is the act of vibrating a wooden stake that has been driven into soil to bring worms to the surface where they can be collected by hand. [33]

Another way to remove invasive earthworms are mustard pours. Mustard pours are 1 gallon of water and 1/3 cup ground yellow mustard seed mixed together. This is better for gardens because it can be poured over soil to drive worms to the surface without harming any plants. [34]

See also

Related Research Articles

<span class="mw-page-title-main">Vermicompost</span> Product of the composting process using various species of worms

Vermicompost (vermi-compost) is the product of the decomposition process using various species of worms, usually red wigglers, white worms, and other earthworms, to create a mixture of decomposing vegetable or food waste, bedding materials, and vermicast. This process is called vermicomposting, with the rearing of worms for this purpose is called vermiculture.

<span class="mw-page-title-main">Grassland</span> Area with vegetation dominated by grasses

A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur naturally on all continents except Antarctica and are found in most ecoregions of the Earth. Furthermore, grasslands are one of the largest biomes on Earth and dominate the landscape worldwide. There are different types of grasslands: natural grasslands, semi-natural grasslands, and agricultural grasslands. They cover 31–69% of the Earth's land area.

<i>Lumbricus terrestris</i> Species of annelid worm

Lumbricus terrestris is a large, reddish worm species thought to be native to Western Europe, now widely distributed around the world. In some areas where it is an introduced species, some people consider it to be a significant pest for out-competing native worms.

<span class="mw-page-title-main">Lumbricidae</span> Family of annelid worms

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 and the United States and throughout Eurasia to Japan. An enigmatic species in Tasmania is Eophila eti. Currently, 670 valid species and subspecies in about 42 genera are recognized. This family includes the majority of earthworm species well known in Europe and Asia.

<i>Bromus tectorum</i> Species of grass

Bromus tectorum, known as downy brome, drooping brome or cheatgrass, is a winter annual grass native to Europe, southwestern Asia, and northern Africa, but has become invasive in many other areas. It now is present in most of Europe, southern Russia, Japan, South Africa, Australia, New Zealand, Iceland, Greenland, North America and western Central Asia. In the eastern US B. tectorum is common along roadsides and as a crop weed, but usually does not dominate an ecosystem. It has become a dominant species in the Intermountain West and parts of Canada, and displays especially invasive behavior in the sagebrush steppe ecosystems where it has been listed as noxious weed. B. tectorum often enters the site in an area that has been disturbed, and then quickly expands into the surrounding area through its rapid growth and prolific seed production.

<span class="mw-page-title-main">Megascolecidae</span> Family of annelid worms

Megascolecidae is a family of earthworms native to Madagascar, Australia, New Zealand, Asia, and North America. All species of the Megascolecidae belong to the Clitellata class. The Megascolecidae comprise a large family of earthworms and they can grow up to 2 meters in length. The intercontinental distribution of Megascolecidae species favours the continental drift theory.

<span class="mw-page-title-main">Temperate deciduous forest</span> Deciduous forest in the temperate regions

Temperate deciduous or temperate broad-leaf forests are a variety of temperate forest 'dominated' by deciduous trees that lose their leaves each winter. They represent one of Earth's major biomes, making up 9.69% of global land area. These forests are found in areas with distinct seasonal variation that cycle through warm, moist summers, cold winters, and moderate fall and spring seasons. They are most commonly found in the Northern Hemisphere, with particularly large regions in eastern North America, East Asia, and a large portion of Europe, though smaller regions of temperate deciduous forests are also located in South America. Examples of trees typically growing in the Northern Hemisphere's deciduous forests include oak, maple, basswood, beech and elm, while in the Southern Hemisphere, trees of the genus Nothofagus dominate this type of forest. Temperate deciduous forests provide several unique ecosystem services, including habitats for diverse wildlife, and they face a set of natural and human-induced disturbances that regularly alter their structure.

<span class="mw-page-title-main">Human impact on the nitrogen cycle</span>

Human impact on the nitrogen cycle is diverse. Agricultural and industrial nitrogen (N) inputs to the environment currently exceed inputs from natural N fixation. As a consequence of anthropogenic inputs, the global nitrogen cycle (Fig. 1) has been significantly altered over the past century. Global atmospheric nitrous oxide (N2O) mole fractions have increased from a pre-industrial value of ~270 nmol/mol to ~319 nmol/mol in 2005. Human activities account for over one-third of N2O emissions, most of which are due to the agricultural sector. This article is intended to give a brief review of the history of anthropogenic N inputs, and reported impacts of nitrogen inputs on selected terrestrial and aquatic ecosystems.

<i>Rhamnus cathartica</i> Species of flowering plant in the buckthorn family Rhamnaceae

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 central British Isles south to Morocco, and east to Kyrgyzstan. It was introduced to North America as an ornamental shrub in the early 19th century or perhaps before, and is now naturalized in the northern half of the continent, and is classified as an invasive plant in several US states and in Ontario, Canada.

<span class="mw-page-title-main">Earthworm</span> Terrestrial invertebrate, order Opisthopora

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 Oligochaeta. In classical systems, they were in the order of Opisthopora since the male pores opened posterior to the female pores, although the internal male segments are anterior to the female. Theoretical cladistic studies have placed them in the suborder Lumbricina of the order Haplotaxida, but this may change. Other slang names for earthworms include "dew-worm", "rainworm", "nightcrawler", and "angleworm". Larger terrestrial earthworms are also called megadriles as opposed to the microdriles in the semiaquatic families Tubificidae, Lumbricidae and Enchytraeidae. The megadriles are characterized by a distinct clitellum and a vascular system with true capillaries.

<span class="mw-page-title-main">Plant litter</span> Dead plant material that has fallen to the ground

Plant litter is dead plant material that have fallen to the ground. This detritus or dead organic material and its constituent nutrients are added to the top layer of soil, commonly known as the litter layer or O horizon. Litter is an important factor in ecosystem dynamics, as it is indicative of ecological productivity and may be useful in predicting regional nutrient cycling and soil fertility.

<i>Amynthas</i> Genus of annelid worms

Amynthas is a genus of earthworms in the family Megascolecidae. They are known as jumping worms, snake worms, or crazy worms because of their erratic thrashing behaviour when disturbed. The genus is native to East Asia, but they are invasive in many areas of the United States. They are a matter of concern in many states, as they disrupt the native forest ecology by affecting soil structure and chemistry.

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.

<i>Dendrodrilus rubidus</i> Species of annelid worm

Dendrodrilus rubidus is a species of earthworm in the family Lumbricidae. It is native to Europe, and it is a widespread introduced species, occurring on every continent except Antarctica, as well as many islands. It is often invasive. It is sometimes used as fishing bait, and is marketed under many nonspecific names, including red wiggler, jumping red wiggler, red trout worm, jumbo red worm, and pink worm. Other common names include bank worm, tree worm, and gilt tail.

<span class="mw-page-title-main">Invasibility</span>

Alien species, or species that are not native, invade habitats and alter ecosystems around the world. Invasive species are only considered invasive if they are able to survive and sustain themselves in their new environment. A habitat and the environment around it has natural flaws that make them vulnerable to invasive species. The level of vulnerability of a habitat to invasions from outside species is defined as its invasibility. One must be careful not to get this confused with invasiveness, which relates to the species itself and its ability to invade an ecosystem.

Grizelle González is a soil ecologist working for the United States Forest Service in San Juan, Puerto Rico. She is known for her work on soil ecology, nutrient cycling, and ecosystem ecology at the Sabana Field Research Station in Puerto Rico.

<i>Amynthas agrestis</i> Species of worm

Amynthas agrestis, the Asian jumping worm, is a species of worm in the family Megascolecidae. It has a smooth, glossy, grey or brown body with a milky-white clitellum, and can range from 1.5 to 8 in in length. Amynthas agrestis is native to Japan and the Korean Peninsula, and was introduced to North America due to increased human activity during the 19th century; it is considered to be an invasive species in the United States. Worms within the genus Amynthas reproduce and develop quicker than their European counterparts.

Amynthas tokioensis, the Asian jumping worm, is a species of earthworm in the family Megascolecidae. It is native to Japan and the Korean Peninsula. It is an invasive species in North America.

<i>Octolasion lacteum</i> Species of worm

Octolasion lacteum is a species of earthworm of the genus Octolasion. In New Zealand it has been found in West Coast soils and in Canterbury. They are found in mostly moist areas deep under the soil as they feed in the nutrients within the soil. Unlike other worm species, these are known to survive in acidic soil as well as soil that is not as organic compared to other places. They provide some important roles in the ecosystem as well as threats to other species as well. After a drought, they help the soil get more organic by adding more carbon dioxide in the soil and the waste from the O. lacteum also provides nutrients for the soil. In another case, they can also be invasive in a way that they suck up carbon in the soil which means plants have less causing a disruption to the food web. Lastly, they reproduce by cross parthogenic reproduction.

Harp Lake is an oligotrophic, single-basin lake in Ontario, Canada. The lake covers over 710,000 m2 and has a depth of 37.5 m. Harp Lake does have dimitic stratification and is a temperate lake. Additionally, Harp Lake does not have anaerobic conditions in the water column because it is a relatively deep lake. The water in Harp Lake has a pH of 6.3. This pH is caused by the presence of acids and the lack of alkaline bases.[3] Slightly acidic lakes normally have a granite or siliceous bedrock and they are poorly buffered. Also, these lakes commonly have calcium-poor soils or thin soils.

References

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  24. ↑ Blackmon, James H.; et al. (2019). "Temperature Affects Hatching Success of Cocoons in the Invasive Asian Earthworm Amynthas agrestis from the Southern Appalachians" (PDF). Southeastern Naturalist. 18 (2): 270. doi:10.1656/058.018.0205. S2CID   190864181.
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  26. ↑ Greiner, Holly G.; Kashian, Donna R.; Tiegs, Scott D. (2012). "Impacts of invasive Asian (Amynthas hilgendorfi) and European (Lumbricus rubellus) earthworms in a North American temperate deciduous forest". Biological Invasions. 14 (10): 2017–2027. doi:10.1007/s10530-012-0208-y. ISSN   1387-3547. S2CID   254288917.
  27. ↑ Zhang, Weixin; et al. (2010). "Dietary flexibility aids Asian earthworm invasion in North American forests". Ecology. 91 (7): 2070–2079. doi: 10.1890/09-0979.1 . ISSN   1939-9170. PMID   20715629.
  28. ↑ 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
  29. 1 2 Callaham, Mac A. Jr.; González, Grizelle; Hale, Cynthia M.; Heneghan, Liam; Lachnicht, Sharon L.; Zou, Xiaoming (1 September 2006). "Policy and management responses to earthworm invasions in North America". Biological Invasions Belowground: Earthworms as Invasive Species (PDF). Vol. 8. pp. 1317–1329. doi:10.1007/978-1-4020-5429-7_11. ISBN   978-1-4020-5428-0.{{cite book}}: |journal= ignored (help)
  30. ↑ 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
  31. ↑ F., Hendrix, Paul; J., Bohlen, Patrick (2002-09-01). "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". BioScience. 52 (9): 801. doi: 10.1641/0006-3568(2002)052[0801:EEIINA]2.0.CO;2 . ISSN   0006-3568.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  32. ↑ Madritch, Michael D.; Lindroth, Richard L. (13 May 2008). "Removal of invasive shrubs reduces exotic earthworm populations". Biol. Invasions. 11 (3): 663–671. doi:10.1007/s10530-008-9281-7. S2CID   26504134.
  33. ↑ Catania, Kenneth C. (2008-10-14). "Worm Grunting, Fiddling, and Charming—Humans Unknowingly Mimic a Predator to Harvest Bait". PLOS ONE. 3 (10): e3472. doi: 10.1371/journal.pone.0003472 . ISSN   1932-6203. PMC   2566961 . PMID   18852902.
  34. ↑ Webb, Jennifer D. (2022-12-01). "The making and re-making of places along the St. Louis River in Duluth: From paintings to projects". Journal of Great Lakes Research. 48 (6): 1489–1497. doi:10.1016/j.jglr.2022.04.012. ISSN   0380-1330.
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