Editing Invasive species

{{Short description|Non-native organism causing damage to an established environment}}
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[[File:Beaver dam in Tierra del Fuego.jpg|thumb|[[Beaver eradication in Tierra del Fuego|North American beaver dam in Tierra del Fuego]]]]
[[File:Kudzu on trees in Atlanta, Georgia.jpg|thumb|[[Kudzu]], [[Atlanta]]]]
[[File:Kanadische Goldrute, Solidago canadensis - Invasives Unkraut.jpg|right|thumb|[[Solidago canadensis|Canada goldenrod]] as a roadside weed in Poland]]
[[File:Vinca spreading along a border.jpg|thumb|''[[Vinca]]'' in a garden<ref>{{cite web |url=http://www.hear.org/gcw/species/vinca_major/ |title=Global Compendium of Weeds: ''Vinca major'' |publisher=[[Hawaiian Ecosystems at Risk project]] (HEAR) |access-date=February 13, 2020 |archive-date=March 4, 2016 |archive-url=https://web.archive.org/web/20160304030630/http://www.hear.org/gcw/species/vinca_major/ |url-status=live }}</ref>]]

An '''invasive species''' is an [[introduced species]] that harms its new environment.{{r|davis}} Invasive species adversely affect [[habitat]]s and [[bioregion]]s, causing ecological, environmental, and/or economic damage. The term can also be used for native species that become harmful to their native environment after human alterations to its [[food web]].{{citation needed|date=May 2025}} Since the 20th century, invasive species have become serious economic, social, and environmental threats worldwide.

Invasion of long-established ecosystems by organisms is a natural phenomenon, but human-facilitated introductions have greatly increased the rate, scale, and geographic range of invasion. For millennia, humans have served as both accidental and deliberate dispersal agents, beginning with their [[early human migrations|earliest migrations]], accelerating in the [[Age of Discovery]], and accelerating again with [[international trade]]. Notably invasive plant species include the [[kudzu]] vine, [[Heracleum mantegazzianum|giant hogweed]], [[Reynoutria japonica|Japanese knotweed]], and [[Centaurea solstitialis|yellow starthistle]]. Notably invasive animals include [[European rabbit]]s, [[domestic cat]]s, and [[carp]].

== Terminology ==
{{See also |Glossary of invasion biology terms}}

Invasive species are the subset of established non-native alien or naturalized species that are a threat to native species and biodiversity.<ref name="SandlundSchei2001">{{cite book |author1=Odd Terje Sandlund |author2=Peter Johan Schei |author3=Åslaug Viken |title=Invasive Species and Biodiversity Management |url=https://books.google.com/books?id=QHgMqnqaW_YC&pg=PA2 |date=30 June 2001 |publisher=Springer Science & Business Media |isbn=978-0-7923-6876-2 |pages=2– |access-date=November 1, 2020 |archive-date=December 18, 2021 |archive-url=https://web.archive.org/web/20211218042441/https://books.google.com/books?id=QHgMqnqaW_YC&pg=PA2 |url-status=live}}</ref> The term "invasive" is poorly defined and often very subjective.<ref name=neutral/> Invasive species may be plants, animals, fungi, and microbes; some include native species that have invaded human habitats such as farms and landscapes.<ref name="Inderjit2006">{{cite book |author=S. Inderjit |title=Invasive Plants: Ecological and Agricultural Aspects |url=https://books.google.com/books?id=c-aMIwmis-wC&pg=PA252 |date=16 January 2006 |publisher=Springer Science & Business Media |isbn=978-3-7643-7380-1 |pages=252– |access-date=November 1, 2020 |archive-date=December 18, 2021 |archive-url=https://web.archive.org/web/20211218042441/https://books.google.com/books?id=c-aMIwmis-wC&pg=PA252 |url-status=live}}</ref> Some broaden the term to include indigenous or "native" species that have [[Colonisation (biology)|colonized]] natural areas.<ref name=neutral/> Some sources name ''[[Homo sapiens]]'' as an invasive species,<ref>{{cite journal |last=Marean |first=Curtis W. |year=2015 |title=The Most Invasive Species of All |journal=[[Scientific American]] |volume=313 |issue=2 |pages=32–39 |bibcode=2015SciAm.313b..32M |doi=10.1038/scientificamerican0815-32 |jstor=26046104 |pmid=26349141}}</ref><ref>{{cite encyclopedia |year=2015 |title=Invasive species |encyclopedia=[[Encyclopedia Britannica]] |url=https://www.britannica.com/science/invasive-species |access-date=August 18, 2020 |last=Rafferty |first=John P. |archive-url=https://web.archive.org/web/20200802215045/https://www.britannica.com/science/invasive-species |archive-date=August 2, 2020 |quote="...[M]odern humans are among the most successful invasive species." |url-status=live}}</ref> but broad appreciation of human learning capacity and their behavioral potential and [[phenotypic plasticity|plasticity]] may argue against any such fixed categorization.<ref name="root">{{cite journal |last1=Root-Bernstein |first1=Meredith |last2=Ladle |first2=Richard |year=2019 |title=Ecology of a widespread large omnivore, Homo sapiens, and its impacts on ecosystem processes |journal=[[Ecology and Evolution]] |volume=9 |issue=19 |pages=10874–94 |bibcode=2019EcoEv...910874R |doi=10.1002/ece3.5049 |pmc=6802023 |pmid=31641442 |s2cid=203370925 |doi-access=free}}</ref> The definition of "native" can be controversial. For example, the ancestors of ''[[wild horse|Equus ferus]]'' (modern horses) [[Evolution of the horse|evolved]] in [[North America]] and radiated to [[Eurasia]] before becoming extinct in North America. Upon being introduced to North America in 1493 by Spanish [[conquistador]]s, it is debatable whether the [[Feral horse|feral horses]] were native or exotic to the continent of their evolutionary ancestors.<ref>{{cite web |url=http://www.ansp.org/museum/leidy/paleo/equus.php |archive-url=https://web.archive.org/web/20120305215318/http://www.ansp.org/museum/leidy/paleo/equus.php |archive-date=March 5, 2012 |title=Ancient American Horses |last=Leidy |first=Joseph |publisher=[[Academy of Natural Sciences of Drexel University |Academy of Natural Sciences]], [[Drexel University]] |date=March 5, 2012 |access-date=January 10, 2019}}</ref>

While invasive species can be studied within many subfields of biology, most research on invasive organisms has been in [[ecology]] and [[biogeography]]. Much of the work has been influenced by [[Charles Sutherland Elton|Charles Elton's]] 1958 book ''The Ecology of Invasion by Animals and Plants'' which creates a generalized picture of biological invasions.<ref name=IE>{{cite book |last=Lockwood |first=Julie L. |title=Invasion Ecology |year=2007 |publisher=Blackwell Publishing |page=7 |url=http://www.planta.cn/forum/files_planta/invasion_ecology1_208.pdf |author2=Hoopes, Martha F. |author3=Marchetti, Michael P. |access-date=January 21, 2014 |archive-date=September 24, 2015 |archive-url=https://web.archive.org/web/20150924074044/http://www.planta.cn/forum/files_planta/invasion_ecology1_208.pdf}}</ref><ref name=Lowry>{{cite journal |pmid=23404636 |year=2012 |last1=Lowry |first1=E |last2=Rollinson |first2=EJ |last3=Laybourn |first3=AJ |last4=Scott |first4=TE |last5=Aiello-Lammens |first5=ME |last6=Gray |first6=SM |last7=Mickley |first7=J |last8=Gurevitch |first8=J |author-link8=Jessica Gurevitch |title=Biological invasions: A field synopsis, systematic review, and database of the literature |volume=3 |issue=1 |pages=182–96 |doi=10.1002/ece3.431 |pmc=3568853 |journal=[[Ecology and Evolution]]}}</ref> Studies remained sparse until the 1990s.<ref name=Lowry/> This research, largely field observational studies, has disproportionately been concerned with [[terrestrial plant]]s.<ref name=Lowry/> The rapid growth of the field has driven a need to standardize the language used to describe invasive species and events. Despite this, little standard terminology exists; the field lacks any official designation but is commonly referred to as "invasion ecology" or more generally "invasion biology".<ref name=IE/><ref name=Lowry/> This lack of standard terminology has arisen due to the interdisciplinary nature of the field which borrows terms from disciplines such as [[agriculture]], [[zoology]], and [[pathology]], as well as due to studies being performed in isolation.<ref>{{Cite web |title=Invasive Species |publisher=National Geographic Society |url=https://education.nationalgeographic.org/resource/invasive-species |access-date=2022-11-28}}</ref><ref name=IE/>

{|class="wikitable" style="float:right;"
|+Colautti and MacIsaac nomenclature<ref name=neutral/>
|-
! Stage
! Characteristic
|-
|0
|Propagules residing in a donor region
|-
|I
|Traveling
|-
|II
|Introduced
|-
|III
|Localized and numerically rare
|-
|IVa
|Widespread but rare
|-
|IVb
|Localized but dominant
|-
|V
|Widespread and dominant
|}

In an attempt to avoid the ambiguous, subjective, and pejorative vocabulary that so often accompanies discussion of invasive species even in scientific papers, Colautti and MacIsaac proposed a new nomenclature system based on [[biogeography]] rather than on [[taxa]].<ref name=neutral>{{cite journal |last1=Colautti |first1=Robert I. |last2=MacIsaac |first2=Hugh J. |title=A neutral terminology to define 'invasive' species: Defining invasive species |journal=Diversity and Distributions |date=24 February 2004 |volume=10 |issue=2 |pages=135–141 |doi=10.1111/j.1366-9516.2004.00061.x |s2cid=18971654 |doi-access=free }}</ref> By discarding taxonomy, [[human health]], and economic factors, this model focused only on ecological factors. The model evaluated individual populations rather than entire species. It classified each population based on its success in that environment. This model applied equally to indigenous and to introduced species, and did not automatically categorize successful introductions as harmful.<ref name=neutral/>

The USDA's National Invasive Species Information Center defines invasive species very narrowly. According to Executive Order 13112, {{" '}}Invasive species' means an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health."<ref>{{cite web |url=https://www.invasivespeciesinfo.gov/executive-order-13112-section-1-definitions |title=Executive Order 13112 - 1. Definitions |publisher=Ars.usda.gov |access-date=May 27, 2021 |archive-date=June 25, 2021 |archive-url=https://web.archive.org/web/20210625075018/https://www.invasivespeciesinfo.gov/executive-order-13112-section-1-definitions |url-status=live }}</ref>

== Causes ==
Typically, an introduced species must survive at low population densities before it becomes invasive in a new location.<ref name="tilm">{{cite journal |last=Tilman |first=D. |year=2004 |title=Niche tradeoffs, neutrality, and community structure: A stochastic theory of resource competition, invasion, and community assembly |journal=[[Proceedings of the National Academy of Sciences]] |volume=101 |pages=10854–10861 |doi=10.1073/pnas.0403458101 |pmid=15243158 |issue=30 |pmc=503710 |bibcode=2004PNAS..10110854T |doi-access=free }}</ref> At low population densities, it can be difficult for the introduced species to reproduce and maintain itself in a new location, so a species might need to reach a location multiple times before it becomes established. Repeated patterns of human movement, such as ships sailing to and from ports or cars driving up and down highways, offer repeated opportunities for establishment (a high [[propagule pressure]]).<ref name="verl">{{cite journal |last=Verling |first=E. |year=2005 |title=Supply-side invasion ecology: characterizing propagule pressure in coastal ecosystems |journal=[[Proceedings of the Royal Society B]] |volume=272 |pages=1249–1256 |doi=10.1098/rspb.2005.3090 |pmid=16024389 |issue=1569 |pmc=1564104}}</ref> 

=== Ecosystem-based mechanisms ===
In [[ecosystem]]s, the availability of resources determines the impact of additional species on the ecosystem. Stable ecosystems have a resource equilibrium, which can be changed fundamentally by the arrival of invasive species.<ref name="Byers 2002">{{cite journal |last1=Byers |first1=James E. |title=Impact of non-indigenous species on natives enhanced by anthropogenic alteration of selection regimes |journal=Oikos |date=June 2002 |volume=97 |issue=3 |pages=449–458 |doi=10.1034/j.1600-0706.2002.970316.x |bibcode=2002Oikos..97..449B }}</ref> When changes such as a [[forest fire]] occur, normal [[ecological succession]] favors native [[Graminoid|grasses]] and [[forb]]s. An introduced species that can spread faster than natives can outcompete native species for food, squeezing them out. [[Nitrogen]] and [[phosphorus]] are often the limiting factors in these situations.<ref name="Davis 2000 528–534">{{cite journal |last1=Davis |first1=M.A. |last2=Grime |first2=J.P. |last3=Thompson |first3=K. |s2cid=14573817 |year=2000 |title=Fluctuating resources in plant communities: A general theory of invisibility |journal=[[Journal of Ecology]] |volume=88 |issue=3 |pages=528–534 |doi=10.1046/j.1365-2745.2000.00473.x|doi-access=free |bibcode=2000JEcol..88..528D }}</ref> Every species occupies an [[ecological niche]] in its native ecosystem; some species fill large and varied roles, while others are highly specialized. Invading species may occupy unused niches, or create new ones.<ref>{{Cite book |last=Fath |first=Brian D. |title=Encyclopedia of Ecology |url=https://archive.org/details/encyclopediaecol00jorg |url-access=limited |publisher=Elsevier Science |edition=1st |year=2008 |isbn=978-0444520333 |location=Amsterdam, the Netherlands |page=[https://archive.org/details/encyclopediaecol00jorg/page/n1122 1089]}}</ref> For example, [[edge effect]]s describe what happens when part of an ecosystem is disturbed, as in when land is cleared for [[agriculture]]. The boundary between the remaining undisturbed habitat and the newly cleared land itself forms a distinct habitat, creating new winners and losers and possibly hosting species that would not thrive outside the boundary habitat.<ref>{{Cite journal |last1=Alverson |first1=William S. |last2=Waller |first2=Donald M. |last3=Solheim |first3=Stephen L. |date=1988 |title=Forests Too Deer: Edge Effects in Northern Wisconsin |journal=[[Conservation Biology (journal)|Conservation Biology]] |volume=2 |issue=4 |pages=348–358 |doi=10.1111/j.1523-1739.1988.tb00199.x |jstor=2386294|bibcode=1988ConBi...2..348A }}</ref>

In 1958, [[Charles S. Elton]] claimed that ecosystems with higher [[species diversity]] were less subject to invasive species because fewer niches remained unoccupied.<ref name="elton">{{cite book |last=Elton |first=C.S. |others=Foreword by Daniel Simberloff |title=The Ecology of Invasions by Animals and Plants |orig-date=1958 |year=2000 |publisher=University of Chicago Press |location=Chicago |isbn=978-0-226-20638-7 |page=196}}</ref> Other ecologists later pointed to highly diverse, but heavily invaded ecosystems, arguing that ecosystems with high species diversity were more susceptible to invasion.<ref name=Schell>{{cite journal |last1=Stohlgren |first1=Thomas J. |last2=Binkley |first2=Dan |last3=Chong |first3=Geneva W. |last4=Kalkhan |first4=Mohammed A. |last5=Schell |first5=Lisa D. |last6=Bull |first6=Kelly A. |last7=Otsuki |first7=Yuka |last8=Newman |first8=Gregory |last9=Bashkin |first9=Michael |last10=Son |first10=Yowhan |display-authors=6 |title=Exotic Plant Species Invade Hot Spots of Native Plant Diversity |journal=Ecological Monographs |date=February 1999 |volume=69 |issue=1 |pages=25–46 |doi=10.1890/0012-9615(1999)069[0025:EPSIHS]2.0.CO;2 }}</ref> This debate hinged on the [[Scale (spatial)|spatial scale]] of invasion studies. Small-scale studies tended to show a negative relationship between [[Biodiversity|diversity]] and invasion, while large-scale studies tended to show the reverse, perhaps a side-effect of invasives' ability to capitalize on increased resource availability and weaker species interactions that are more common when larger samples are considered.<ref>{{cite journal |last1=Byers |first1=James E. |last2=Noonburg |first2=Erik G. |title=Scale Dependent Effects of Biotic Resistance to Biological Invasion |journal=Ecology |date=June 2003 |volume=84 |issue=6 |pages=1428–1433 |doi=10.1890/02-3131 |bibcode=2003Ecol...84.1428B }}</ref><ref>{{cite journal |last1=Levine |first1=Jonathan M. |title=Species Diversity and Biological Invasions: Relating Local Process to Community Pattern |journal=Science |date=5 May 2000 |volume=288 |issue=5467 |pages=852–854 |doi=10.1126/science.288.5467.852 |pmid=10797006 |bibcode=2000Sci...288..852L }}</ref> However, this pattern does not seem to hold true for invasive vertebrates.{{r|ivey2019}}

[[File:Brown tree snake (Boiga irregularis) (8387580552).jpg|thumb|right|The [[brown tree snake]] has had an impact on the native bird population of the island ecosystem of Guam.]]

[[Island ecosystem]]s may be more prone to invasion because their species face few strong competitors and predators, and because their distance from colonizing species populations makes them more likely to have "open" niches.<ref name="stach">{{cite book |last=Stachowicz |first=J.J. |editor=D.F. Sax |editor2=J.J. Stachowicz |editor3=S.D. Gaines |title=Species Invasions: Insights into Ecology, Evolution, and Biogeography |publisher=Sinauer Associates |location=Sunderland, Massachusetts |isbn=978-0-87893-811-7 |chapter=Species invasions and the relationships between species diversity, community saturation, and ecosystem functioning |year=2005 |url-access=registration |url=https://archive.org/details/speciesinvasions0000unse }}</ref> For example, native bird populations on [[Guam]] have been decimated by the invasive [[brown tree snake]].<ref>{{Cite web |title=Brown Tree Snake |url=https://www.invasivespeciesinfo.gov/profile/brown-tree-snake |url-status=live |archive-url=https://web.archive.org/web/20190824120114/https://www.invasivespeciesinfo.gov/profile/brown-tree-snake |archive-date=24 August 2019 |website=USDA National Invasive Species Information Center}}</ref> 

In [[Invasive species in New Zealand|New Zealand]] the first invasive species were the dogs and [[Polynesian rat|rats]] brought by Polynesian settlers around 1300. These and other introductions devastated endemic New Zealand species.<ref>{{cite book |last=Howe |first=K. R. |title=The Quest for Origins |year=2003 |page=179 |publisher=Penguin Books |isbn=0-14-301857-4}}</ref><ref>{{Cite news |date=4 June 2008 |title=Rat remains help date New Zealand's colonisation |work=New Scientist |url=https://www.newscientist.com/article/mg19826595-200-rat-remains-help-date-new-zealands-colonisation/?ignored=irrelevant |url-status=live |url-access=subscription |access-date=23 June 2008 |archive-url=https://web.archive.org/web/20220611120716/https://www.newscientist.com/article/mg19826595-200-rat-remains-help-date-new-zealands-colonisation/?ignored=irrelevant |archive-date=11 June 2022}}</ref> The colonization of [[Madagascar]] brought similar harm to its ecosystems.<ref>{{cite journal |last1=Goodman |first1=Steven M. |date=1997 |title=The birds of southeastern Madagascar |journal=Fieldiana |issue=87 |doi=10.5962/bhl.title.3415 |doi-access=free}}</ref> Logging has caused harm directly by destroying habitat, and has allowed non-native species such as [[Opuntia|prickly pear]] and [[Acacia dealbata|silver wattle]] to invade.<ref>{{cite journal |last1=Brown |first1=Kerry A. |last2=Gurevitch |first2=Jessica |title=Long-term impacts of logging on forest diversity in Madagascar |journal=Proceedings of the National Academy of Sciences |date=20 April 2004 |volume=101 |issue=16 |pages=6045–6049 |doi=10.1073/pnas.0401456101 |pmid=15067121 |pmc=395920 |bibcode=2004PNAS..101.6045B |doi-access=free }}</ref><ref>{{cite journal |last1=Kull |first1=Ca |last2=Tassin |first2=J |last3=Carriere |first3=Sm |title=Approaching invasive species in Madagascar |journal=Madagascar Conservation & Development |date=26 February 2015 |volume=9 |issue=2 |pages=60 |doi=10.4314/mcd.v9i2.2 |doi-access=free }}</ref> The [[Eichhornia crassipes|water hyacinth]] forms dense mats on water surfaces, limiting light penetration and hence harming aquatic organisms, and causing substantial management costs.<ref>{{cite journal |last1=Villamagna |first1=A. M. |last2=Murphy |first2=B. R. |title=Ecological and socio-economic impacts of invasive water hyacinth (''Eichhornia crassipes''): a review |journal=Freshwater Biology |date=February 2010 |volume=55 |issue=2 |pages=282–298 |doi=10.1111/j.1365-2427.2009.02294.x |bibcode=2010FrBio..55..282V }}</ref><ref name="Rakotoarisoa 365–379">{{cite journal |last1=Rakotoarisoa |first1=T. F. |last2=Richter |first2=T. |last3=Rakotondramanana |first3=H. |last4=Mantilla-Contreras |first4=J. |title=Turning a Problem Into Profit: Using Water Hyacinth (''Eichhornia crassipes'') for Making Handicrafts at Lake Alaotra, Madagascar |journal=Economic Botany |date=December 2016 |volume=70 |issue=4 |pages=365–379 |doi=10.1007/s12231-016-9362-y |bibcode=2016EcBot..70..365R |s2cid=255557151 |id = {{s2cid|18820290}} }}</ref> The shrub lantana (''[[Lantana camara]]'') is now considered invasive in over 60 countries, and has invaded large geographies in several countries prompting aggressive federal efforts at attempting to control it.<ref>{{Cite journal |last1=Bhagwat |first1=Shonil A. |last2=Breman |first2=Elinor |last3=Thekaekara |first3=Tarsh |last4=Thornton |first4=Thomas F. |last5=Willis |first5=Katherine J. |date=2012 |title=A Battle Lost? Report on Two Centuries of Invasion and Management of Lantana camara L. in Australia, India and South Africa |journal=PLOS ONE |language=en |volume=7 |issue=3 |pages=e32407 |doi=10.1371/journal.pone.0032407 |doi-access=free |pmc=3293794 |pmid=22403653|bibcode=2012PLoSO...732407B }}</ref><ref>{{Cite journal |last1=Mungi |first1=Ninad Avinash |last2=Qureshi |first2=Qamar |last3=Jhala |first3=Yadvendradev V. |date=2020 |title=Expanding niche and degrading forests: Key to the successful global invasion of Lantana camara (sensu lato) |journal=Global Ecology and Conservation |volume=23 |pages=e01080 |doi=10.1016/j.gecco.2020.e01080 |doi-access=free |bibcode=2020GEcoC..2301080M }}</ref>  

Primary geomorphological effects of invasive plants are bioconstruction and bioprotection. For example, kudzu (''[[Pueraria montana]]''), a vine native to Asia, was widely introduced in the [[Southeastern US|southeastern United States]] in the early 20th century to control [[soil erosion]]. The primary geomorphological effects of invasive animals are [[bioturbation]], [[bioerosion]], and bioconstruction. For example, invasions of the Chinese mitten crab (''[[Eriocheir sinensis]]'') have resulted in higher bioturbation and bioerosion rates.<ref>{{cite journal |last1=Fei |first1=Songlin |last2=Phillips |first2=Jonathan |last3=Shouse |first3=Michael |title=Biogeomorphic Impacts of Invasive Species |journal=Annual Review of Ecology, Evolution, and Systematics |date=23 November 2014 |volume=45 |issue=1 |pages=69–87 |doi=10.1146/annurev-ecolsys-120213-091928 |doi-access=free }}</ref>

A native species can become harmful and effectively invasive to its native environment after human alterations to its [[food web]]. This has been the case with the purple sea urchin (''[[Strongylocentrotus purpuratus]]''), which has decimated kelp forests along the northern California coast due to overharvesting of its natural predator, the California sea otter (''[[Sea otter|Enhydra lutris]]'').<ref>{{Cite web |title=Plague of purple sea urchins ravages California's offshore ecosystem, heads to Oregon |website=[[Los Angeles Times]]|date=October 24, 2019|url=https://www.latimes.com/california/story/2019-10-24/purple-sea-urchins-california-oregon-coasts|access-date=July 14, 2021 |archive-date=July 14, 2021 |archive-url=https://web.archive.org/web/20210714030639/https://www.latimes.com/california/story/2019-10-24/purple-sea-urchins-california-oregon-coasts |url-status=live}}</ref>

===Species-based mechanisms===
[[File:Riesenknoeterich.jpg|right|thumb|Japanese knotweed (''[[Reynoutria japonica]]'') is considered one of the [[100 of the World's Worst Invasive Alien Species|world's worst invasive species]].]]
[[File:Ocicat-woodpecker.jpg|upright|thumb|Cats (here, killing a [[woodpecker]]) are [[Cats in Australia|considered invasive species]] in Australia and [[Cat predation on wildlife|negatively impact wildlife]] worldwide.]]

Invasive species appear to have specific traits or specific combinations of traits that allow them to outcompete [[native species]]. In some cases, the competition is about rates of growth and reproduction. In other cases, species interact with each other more directly. One study found that 86% of invasive species could be identified from such traits alone.<ref name="kolar">{{cite journal |last=Kolar |first=C.S. |year=2001 |title=Progress in invasion biology: predicting invaders|journal=[[Trends in Ecology & Evolution]] |volume=16 |issue=4 |pages=199–204 |doi=10.1016/S0169-5347(01)02101-2 |pmid=11245943|s2cid=5796978 }}</ref> Another study found that invasive species often had only a few of the traits, and that noninvasive species had these also.<ref name="kolar"/><ref name="theb">{{cite journal |last=Thebaud |first=C. |year=1996 |title=Assessing why two introduced Conyza differ in their ability to invade Mediterranean old fields |journal=Ecology |volume=77 |issue=3 |pages=791–804 |doi=10.2307/2265502 |jstor=2265502 |bibcode=1996Ecol...77..791T }}</ref><ref name="reichard">{{cite journal |last=Reichard |first=S.H. |s2cid=29816498 |year=1997 |title=Predicting invasions of woody plants introduced into North America |journal=[[Conservation Biology (journal)|Conservation Biology]] |volume=11 |issue=1 |pages=193–203 |doi=10.1046/j.1523-1739.1997.95473.x |pmc=7162396}}</ref> Common invasive species traits include fast growth and rapid [[reproduction]], such as [[vegetative reproduction]] in plants;<ref name="kolar"/><!--high [[Biological dispersal|dispersal]] ability;--><!--[[Phenotypic plasticity|Phenotype plasticity]];--><!--[[ecological competence]];--><!--[[Generalist and specialist species|generalist]];--> association with humans;<ref name="Williams">{{cite book |last=Williams |first=J. D. |year=1998 |chapter=Non-indigenous Species |title=Status and Trends of the Nation's Biological Resources |location=[[Reston, Virginia]] |pages=117–29 |publisher=[[United States Geological Survey]] |isbn=978-0-16-053285-6 |id={{DTIC|ADA368849}} }}</ref> and prior successful invasions.<ref name="ewell">{{cite journal |last=Ewell |first=J.J. |year=1999 |title=Deliberate introductions of species: Research needs – Benefits can be reaped, but risks are high |journal=[[BioScience]] |volume=49 |pages=619–630 |doi=10.2307/1313438 |jstor=1313438 |issue=8 |doi-access=free |bibcode=1999BiSci..49..619E }}</ref> [[Domestic cat]]s are effective predators; they have become feral and invasive in places such as the [[Florida Keys]].<ref name="Cove Gardner 2018">{{cite journal |last1=Cove |first1=Michael V. |last2=Gardner |first2=Beth |last3=Simons |first3=Theodore R. |last4=Kays |first4=Roland |last5=O'Connell |first5=Allan F. |s2cid=3536174 |date=February 1, 2018 |title=Free-ranging domestic cats (''Felis catus'') on public lands: estimating density, activity, and diet in the Florida Keys |journal=[[Biological Invasions]] |volume=20 |issue=2 |pages=333–344 |doi=10.1007/s10530-017-1534-x|bibcode=2018BiInv..20..333C }}</ref>

An introduced species might become invasive if it can outcompete native species for resources. If these species evolved under great [[Competition (biology)|competition]] or [[predation]], then the new environment may host fewer able competitors, allowing the invader to proliferate. [[Ecosystem]]s used to their fullest capacity by native species can be modeled as [[zero-sum]] systems, in which any gain for the invader is a loss for the native. However, such [[unilateral]] competitive superiority (and extinction of native species with increased populations of the invader) is not the rule.<ref name="Schell"/><ref name="sax">{{cite journal |last1=Sax |first1=Dov F. |last2=Gaines |first2=Steven D. |last3=Brown |first3=James H. |title=Species Invasions Exceed Extinctions on Islands Worldwide: A Comparative Study of Plants and Birds |journal=The American Naturalist |date=December 2002 |volume=160 |issue=6 |pages=766–783 |doi=10.1086/343877 |pmid=18707464 |s2cid=8628360 }}</ref> 

[[File:Lantana Invasion of abandoned citrus plantation Sdey Hemed Israel.JPG|right|thumb|upright=1.8|[[Lantana]], abandoned [[citrus grove|citrus]], [[Sdei Hemed]]]]

An invasive species might be able to use resources previously unavailable to native species, such as deep water accessed by a long [[taproot]], or to live on previously uninhabited soil types. For example, [[Aegilops triuncialis|barbed goatgrass]] was introduced to [[California]] on [[serpentine soil]]s, which have low water-retention, low nutrient levels, a high [[magnesium]]/[[calcium]] ratio, and possible [[Heavy metal (chemistry)|heavy metal]] toxicity. Plant populations on these soils tend to show low density, but goatgrass can form dense stands on these soils and crowd out native species.<ref>{{cite journal |last1=Huenneke |first1=Laura Foster |last2=Hamburg |first2=Steven P. |last3=Koide |first3=Roger |last4=Mooney |first4=Harold A. |last5=Vitousek |first5=Peter M. |title=Effects of Soil Resources on Plant Invasion and Community Structure in Californian Serpentine Grassland |journal=Ecology |date=1990 |volume=71 |issue=2 |pages=478–491 |doi=10.2307/1940302 |jstor=1940302 |bibcode=1990Ecol...71..478H }}</ref>

Invasive species might alter their environment by releasing chemical compounds, modifying [[abiotic]] factors, or affecting the behaviour of [[herbivore]]s, impacting on other species. Some, like ''[[Bryophyllum daigremontianum|Kalanchoe daigremontana]]'', produce [[allelopathy|allelopathic compounds]] that inhibit competitors.<ref name="HERRERAFERRER-PARIS2018">{{cite journal |title=An Invasive Succulent Plant (Kalanchoe daigremontiana) Influences Soil Carbon and Nitrogen Mineralization in a Neotropical Semiarid Zone |journal=[[Pedosphere]] |volume=28 |issue=4 |year=2018 |pages=632–643 |doi=10.1016/S1002-0160(18)60029-3 |last1=Herrera |first1=Ileana |last2=Ferrer-Paris |first2=José R. |last3=Benzo |first3=Diana |last4=Flores |first4=Saúl |last5=García |first5=Belkis |last6=Nassar |first6=Jafet M. |bibcode=2018Pedos..28..632H |hdl=1959.4/unsworks_64013 |s2cid=104843296|url=https://unsworks.unsw.edu.au/bitstreams/12acbbad-8af9-444b-a478-e7dc9d941d9b/download |hdl-access=free }}</ref> Others like ''[[Stapelia gigantea]]'' [[ecological facilitation|facilitate]] the growth of seedlings of other species in arid environments by providing appropriate [[microclimate]]s and preventing herbivores from eating seedlings.<ref>{{cite journal |last1=Herrera |first1=Ileana |last2=Ferrer-Paris |first2=José R. |last3=Hernández-Rosas |first3=José I. |last4=Nassar |first4=Jafet M. |title=Impact of two invasive succulents on native-seedling recruitment in Neotropical arid environments |journal=[[Journal of Arid Environments]] |date=2016 |volume=132 |pages=15–25 |doi=10.1016/j.jaridenv.2016.04.007 |bibcode=2016JArEn.132...15H}}</ref>

Changes in [[fire regime]]ns are another form of facilitation. ''[[Bromus tectorum]]'', originally from Eurasia, is highly fire-adapted. It spreads rapidly after burning, and increases the frequency and intensity of fires by providing large amounts of dry [[detritus]] during the fire season in western North America. Where it is widespread, it has altered the local fire regimen so much that native plants cannot survive the frequent fires, allowing it to become dominant in its introduced range.<ref name="Brooks 2004 677–688">{{cite journal |last1=Brooks |first1=Matthew L. |last2=D'Antonio |first2=Carla M. |last3=Richardson |first3=David M. |last4=Grace |first4=James B. |last5=Keeley |first5=Jon E. |last6=DiTOMASO |first6=Joseph M. |last7=Hobbs |first7=Richard J. |last8=Pellant |first8=Mike |last9=Pyke |first9=David |title=Effects of Invasive Alien Plants on Fire Regimes |journal=BioScience |date=2004 |volume=54 |issue=7 |pages=677 |doi=10.1641/0006-3568(2004)054[0677:EOIAPO]2.0.CO;2 |s2cid=13769125 |doi-access=free }}</ref>

[[Ecological facilitation]] occurs where one species physically modifies a habitat in ways advantageous to other species. For example, [[zebra mussel]]s increase habitat complexity on lake floors, providing crevices in which [[invertebrate]]s live. This increase in complexity, together with the nutrition provided by the waste products of mussel [[filter feeder|filter-feeding]], increases the density and diversity of [[Benthic zone|benthic]] invertebrate communities.<ref name="silv">{{cite journal |last1=Silver Botts |first1=P. |last2=Patterson |first2=B.A. |last3=Schlosser |first3=D. |year=1996 |title=Zebra mussel effects on benthic invertebrates: Physical or biotic? |journal=[[Journal of the North American Benthological Society]] |issue=2 |volume=15 |doi=10.2307/1467947 |jstor=1467947 |pages=179–184 |s2cid=84660670 }}</ref>

Introduced species may spread rapidly and unpredictably.<ref>{{Cite book |last=Keddy |first=Paul A. |url=https://books.google.com/books?id=ncloDgAAQBAJ&q=Plant+Ecology |title=Plant Ecology |publisher=Cambridge University Press |year=2017 |isbn=978-1-107-11423-4 |pages=343 |access-date=October 6, 2020 |archive-date=August 16, 2021 |archive-url=https://web.archive.org/web/20210816224645/https://books.google.com/books?id=ncloDgAAQBAJ&q=Plant+Ecology |url-status=live}}</ref> When [[Population bottleneck|bottlenecks]] and [[founder effect]]s cause a great decrease in the population size and may constrict [[genetic variation]],<ref>{{Cite journal |last1=Xu |first1=Cheng-Yuan |last2=Tang |first2=Shaoqing |last3=Fatemi |first3=Mohammad |last4=Gross |first4=Caroline L. |last5=Julien |first5=Mic H. |last6=Curtis |first6=Caitlin |last7=van Klinken |first7=Rieks D. |date=September 1, 2015 |title=Population structure and genetic diversity of invasive Phyla canescens: implications for the evolutionary potential |journal=[[Ecosphere (journal)|Ecosphere]] |volume=6 |issue=9 |pages=art162 |doi=10.1890/ES14-00374.1 |doi-access=free}}</ref> the individuals begin to show additive variance as opposed to epistatic variance. This conversion can lead to increased variance in the founding populations, which permits [[rapid evolution]].<ref name="Prentis 2008 288-294">{{cite journal |last=Prentis |first=Peter |title=Adaptive evolution in invasive species |journal=[[Trends in Plant Science]]|volume=13 |issue=6 |pages=288–294 |doi=10.1016/j.tplants.2008.03.004 |pmid=18467157 |year=2008|bibcode=2008TPS....13..288P |hdl=10019.1/112332 |hdl-access=free }}</ref> Selection may then act on the capacity to disperse as well as on physiological tolerance to new stressors in the environment, such as changed temperature and different predators and prey.<ref name="Eunmi 2002 386-391">{{cite journal |last=Lee |first=Carol Eunmi |title=Evolutionary genetics of invasive species |journal=[[Trends in Ecology & Evolution]]|volume=17 |issue=8 |pages=386–391 |doi=10.1016/s0169-5347(02)02554-5 |year=2002}}</ref> 

Rapid adaptive evolution through intraspecific phenotypic plasticity, [[Exaptation|pre-adaptation]] and post-introduction evolution lead to offspring that have higher fitness. Critically, plasticity permits changes to better suit the individual to its environment. Pre-adaptations and evolution after the introduction reinforce the success of the introduced species.<ref name="Zenni 2013 635-644">{{cite journal |last=Zenni |first=R.D. |title=Adaptive Evolution and Phenotypic Plasticity During Naturalization and Spread of Invasive Species: Implications for Tree Invasion Biology |journal=[[Biological Invasions]] |year=2013 |volume=16 |issue=3 |pages=635–644 |doi=10.1007/s10530-013-0607-8 |s2cid=82590}}</ref>

The [[enemy release hypothesis]] states that evolution leads to ecological balance in every ecosystem. No single species can occupy a majority of an ecosystem due to the presences of competitors, predators, and diseases. Introduced species moved to a novel habitat can become invasive, with rapid population growth, when these controls do not exist in the new ecosystem.{{r|amstutz2018}}

==Vectors==
Non-native species have many [[Vector (epidemiology)|vector]]s, but most are associated with human activity. Natural [[Range (biology)|range]] extensions are common, but humans often carry specimens faster and over greater distances than natural forces.<ref>{{cite journal |last=Cassey |first=P |year=2005 |title=Concerning Invasive Species: Reply to Brown and Sax|journal=[[Austral Ecology]] |volume=30|issue=4 |pages=475–480 |doi=10.1111/j.1442-9993.2005.01505.x|bibcode=2005AusEc..30..475C |hdl=10019.1/119884 |hdl-access=free}}</ref> An early human vector occurred when prehistoric humans introduced the Pacific rat (''Rattus exulans'') to Polynesia.<ref>{{cite journal |last=Matisoo-Smith |first=E. |year=1998 |title=Patterns of prehistoric human mobility in Polynesia indicated by mtDNA from the Pacific rat|journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=95 |pages=15145–15150 |doi=10.1073/pnas.95.25.15145 |pmid=9844030 |issue=25 |pmc=24590 |bibcode=1998PNAS...9515145M |doi-access=free }}</ref>

[[File:EriocheirSinensis1.jpg|thumb|left|[[Chinese mitten crab]] ]]

Vectors include plants or seeds imported for [[horticulture]]. The [[pet trade]] moves animals across borders, where they can escape and become invasive. Organisms stow away on transport vehicles. Incidental human assisted transfer is the main cause of introductions{{snd}}other than for [[polar regions of Earth|polar regions]].<ref name="Essl-et-al-2020">{{cite journal |last1=Essl |first1=Franz |last2=Lenzner |first2=Bernd |last3=Bacher |first3=Sven |last4=Bailey |first4=Sarah |last5=Capinha |first5=Cesar |last6=Daehler |first6=Curtis |last7=Dullinger |first7=Stefan |last8=Genovesi |first8=Piero |last9=Hui |first9=Cang |last10=Hulme |first10=Philip E. |last11=Jeschke |first11=Jonathan M. |last12=Katsanevakis |first12=Stelios |display-authors=6 |title=Drivers of future alien species impacts: An expert-based assessment |journal=Global Change Biology |date=September 2020 |volume=26 |issue=9 |pages=4880–4893 |doi=10.1111/gcb.15199 |pmid=32663906 |pmc=7496498 |bibcode=2020GCBio..26.4880E }}</ref> Diseases may be vectored by invasive insects: the [[Diaphorina citri|Asian citrus psyllid]] carries the bacterial disease [[Citrus greening disease|citrus greening]].<ref name=r2/> The arrival of invasive [[propagule]]s to a new site is a function of the site's invasibility.<ref>{{cite journal |last=Leung |first=B. |year=2007 |title=The risk of establishment of aquatic invasive species: joining invasibility and propagule pressure |journal=[[Proceedings of the Royal Society B]] |volume=274 |pages=2733–2739|doi=10.1098/rspb.2007.0841 |pmid=17711834 |issue=1625 |pmc=2275890}}</ref>

Many invasive species, once they are dominant in the area, become essential to the ecosystem of that area, and their removal could be harmful.<ref>{{cite journal |last1=Zavaleta |first1=Erika S. |last2=Hobbs |first2=Richard J. |last3=Mooney |first3=Harold A. |title=Viewing invasive species removal in a whole-ecosystem context |journal=Trends in Ecology & Evolution |date=August 2001 |volume=16 |issue=8 |pages=454–459 |doi=10.1016/s0169-5347(01)02194-2 }}</ref> Economics plays a major role in exotic species introduction. High demand for the valuable [[Chinese mitten crab]] is one explanation for the possible intentional release of the species in foreign waters.<ref>{{Cite book |last=Seinfeld |first=John H. |title=Marine Pollution and Climate Change |publisher=[[John Wiley & Sons]] |year=2016 |isbn=9781482299441 |editor-last=Arias |editor-first=Andres Hugo |editor-last2=Marcovecchio |editor-first2=Jorge Eduardo}}</ref>

=== Within the aquatic environment ===
Maritime trade has rapidly affected the way marine organisms are transported within the ocean; new means of species transport include hull fouling and ballast water transport. In fact, Molnar et al. 2008 documented the pathways of hundreds of marine invasive species and found that shipping was the dominant mechanism for the transfer of invasive species.<ref>{{cite journal |last1=Molnar |first1=Jennifer L. |last2=Gamboa |first2=Rebecca L. |last3=Revenga |first3=Carmen |last4=Spalding |first4=Mark D. |title=Assessing the global threat of invasive species to marine biodiversity |journal=Frontiers in Ecology and the Environment |date=November 2008 |volume=6 |issue=9 |pages=485–492 |doi=10.1890/070064 |bibcode=2008FrEE....6..485M }}</ref> 

[[File:CSIRO ScienceImage 1010 Discharging ballast water.jpg |thumb |Cargo ship [[sailing ballast |de-ballasting]] ]]

Many marine organisms can attach themselves to vessel hulls. Such organisms are easily transported from one body of water to another, and are a significant risk factor for a biological invasion event.<ref>{{Cite journal |last=Drake |first=John |date=2007 |title=Hull fouling is a risk factor for intercontinental species exchange in aquatic ecosystems |journal=[[Aquatic Invasions]] |volume=2 |issue=2 |pages=121–131 |doi=10.3391/ai.2007.2.2.7 |doi-access=free}}</ref> Controlling for vessel hull fouling is voluntary and there are no regulations currently in place to manage hull fouling. However, the governments of [[California]] and [[New Zealand]] have announced more stringent control for vessel hull fouling within their respective jurisdictions.<ref>{{cite web |url=http://www.gard.no/web/updates/content/24305557/biofouling-moves-up-the-regulatory-agenda. |title=Biofouling moves up the regulatory agenda – GARD |website=www.gard.no |access-date=September 19, 2018 |archive-date=January 13, 2020 |archive-url=https://web.archive.org/web/20200113231807/http://www.gard.no/web/updates/content/24305557/biofouling-moves-up-the-regulatory-agenda. |url-status=live}}</ref>

Another vector of non-native aquatic species is [[Ballast water discharge and the environment|ballast water]] taken up at sea and released in port by transoceanic vessels.<ref name=cargo>{{cite web |url=http://www.jsonline.com/news/wisconsin/98880204.html |last=Egan |first=Dan |work=[[Journal Sentinel]] |date=October 31, 2005 |title=Noxious cargo |access-date=April 22, 2017 |archive-url=https://web.archive.org/web/20111021122316/http://www.jsonline.com/news/wisconsin/98880204.html |archive-date=October 21, 2011 }}</ref><ref>{{cite book |doi=10.1145/2623330.2623364 |chapter=Improving management of aquatic invasions by integrating shipping network, ecological, and environmental data |title=Proceedings of the 20th ACM SIGKDD international conference on Knowledge discovery and data mining |year=2014 |last1=Xu |first1=Jian |last2=Wickramarathne |first2=Thanuka L. |last3=Chawla |first3=Nitesh V. |last4=Grey |first4=Erin K. |last5=Steinhaeuser |first5=Karsten |last6=Keller |first6=Reuben P. |last7=Drake |first7=John M. |last8=Lodge |first8=David M. |pages=1699–1708 |isbn=978-1-4503-2956-9 |s2cid=2371978 }}</ref> Some 10,000 species are transported via ballast water each day.<ref>{{Cite journal |last1=Streftaris |first1=N |last2=Zenetos |first2=Argyro |last3=Papathanassiou |first3=Enangelos |date=2005 |title=Globalisation in marine ecosystems: The story of non-indigenous marine species across European seas |url=https://www.researchgate.net/publication/253862066 |journal=[[Oceanography and Marine Biology]] |volume=43 |pages=419–453 |access-date=September 19, 2018 |archive-date=September 20, 2018 |archive-url=https://web.archive.org/web/20180920011308/https://www.researchgate.net/publication/253862066 |url-status=live}}</ref> Many of these are harmful. For example, freshwater [[zebra mussel]]s from Eurasia most likely reached the [[Great Lakes]] via ballast water.{{r|pnwaquaticinv}} These outcompete native organisms for oxygen and food, and can be transported in the small puddle left in a supposedly empty ballast tank.<ref name=cargo/> Regulations attempt to mitigate such risks,<ref>{{cite web |url=https://www.glc.org/wp-content/uploads/GLC-BW-Reg-Summary-11.14.16.pdf |title=Status of Ballast Water Discharge Regulations in the Great Lakes Region |last=Great Lake Commission |access-date=September 19, 2018 |archive-date=February 12, 2020 |archive-url=https://web.archive.org/web/20200212212419/http://www.glc.org/wp-content/uploads/GLC-BW-Reg-Summary-11.14.16.pdf |url-status=live}}</ref><ref>{{cite web |url=https://www.dco.uscg.mil/Portals/9/DCO%20Documents/5p/5ps/NVIC/2018/NVIC-01_18.pdf |title=Ballast Water Management for Control of Non-Indigenous Species in Waters of the United States |last=USCG |access-date=September 19, 2018 |archive-date=May 11, 2020 |archive-url=https://web.archive.org/web/20200511133624/https://www.dco.uscg.mil/Portals/9/DCO%20Documents/5p/5ps/NVIC/2018/NVIC-01_18.pdf |url-status=live}}</ref> not always successfully.{{r |trainer2012}} 

[[Climate change]] is causing an increase in [[ocean temperature]]. This in turn will cause range shifts in organisms,<ref>{{Cite journal |last=Occhipinti-Ambrogi |first=Anna |date=2007 |title=Global change and marine communities: Alien species and climate change |journal=[[Marine Pollution Bulletin]] |volume=55 |issue=7–9 |pages=342–352 |doi=10.1016/j.marpolbul.2006.11.014 |pmid=17239404 |bibcode=2007MarPB..55..342O }}</ref><ref>{{cite journal |last1=Rahel |first1=Frank J. |last2=Olden |first2=Julian D. |title=Assessing the Effects of Climate Change on Aquatic Invasive Species |journal=Conservation Biology |date=June 2008 |volume=22 |issue=3 |pages=521–533 |doi=10.1111/j.1523-1739.2008.00950.x |pmid=18577081 |s2cid=313824 |doi-access=free |bibcode=2008ConBi..22..521R }}</ref> which could harm the environment as new species interactions occur. For example, organisms in a ballast tank of a ship traveling from the temperate zone through tropical waters may experience temperature fluctuations as much as 20&nbsp;°C.<ref>{{Cite journal |last1=Hua |first1=J. |last2=Hwang |first2=W.H. |date=2012 |title=Effects of voyage routing on the survival of microbes in ballast water |journal=[[Ocean Engineering]] |volume=42 |pages=165–175 |doi=10.1016/j.oceaneng.2012.01.013|bibcode=2012OcEng..42..165H }}</ref> Heat challenges during transport may enhance the stress tolerance of species in their non-native range, by selecting for genotypes that will survive a second applied heat stress, such as increased ocean temperature in the founder population.<ref>{{Cite journal |last1=Lenz |first1=Mark |last2=Ahmed |first2=Yasser |last3=Canning-Clode |first3=João |last4=Díaz |first4=Eliecer |last5=Eichhorn |first5=Sandra |last6=Fabritzek |first6=Armin G. |last7=da Gama |first7=Bernardo A. P. |last8=Garcia |first8=Marie |last9=von Juterzenka |first9=Karen |s2cid=53082967 |date=May 24, 2018 |title=Heat challenges can enhance population tolerance to thermal stress in mussels: a potential mechanism by which ship transport can increase species invasiveness |journal=[[Biological Invasions]] |volume=20 |issue=11 |pages=3107–3122 |doi=10.1007/s10530-018-1762-8|bibcode=2018BiInv..20.3107L }}</ref>

=== Effects of wildfire and firefighting ===
Invasive species often exploit disturbances to an ecosystem ([[wildfire]]s, [[road]]s, [[foot trail]]s) to colonize an area. Large wildfires can [[Sterilization (microbiology)|sterilize]] soils, while adding [[nutrient]]s.<ref name="Davis 2000 528–534"/> 
Invasive plants that can regenerate from their roots then have an advantage over natives that rely on seeds for propagation.<ref name="Brooks 2004 677–688"/>

==Adverse effects==
Invasive species can affect the invaded habitats and bioregions adversely, causing ecological, environmental, or economic damage.{{r|ehrenfeld2010}}

===Ecological===
The European Union defines "Invasive Alien Species" as those that are outside their natural distribution area, and that threaten [[biological diversity]].<ref>{{cite web |url=http://ec.europa.eu/environment/nature/invasivealien/docs/1_EN_resume_impact_assesment_part1_v3.pdf |title=Communication From The Commission To The Council, The European Parliament, The European Economic And Social Committee And The Committee Of The Regions Towards An EU Strategy On Invasive Species |access-date=May 17, 2011 |archive-date=March 5, 2016 |archive-url=https://web.archive.org/web/20160305033628/http://ec.europa.eu/environment/nature/invasivealien/docs/1_EN_resume_impact_assesment_part1_v3.pdf |url-status=live }}</ref><ref>{{cite journal |doi=10.2298/ZMSPN1834019L |title=Non-native and invasive tree species - their impact on biodiversity loss |year=2018 |last1=Lakicevic |first1=Milena |last2=Mladenovic |first2=Emina |journal=[[Zbornik Matice Srpske za Prirodne Nauke]] |issue=134 |pages=19–26 |doi-access=free}}</ref> Biotic invasion is one of the five top drivers for global [[biodiversity loss]], and is increasing because of tourism and [[globalization]].<ref>{{Cite book |url=https://www.nap.edu/read/10259/chapter/1 |year=2002 |doi=10.17226/10259 |pmid=25032288 |isbn=978-0-309-08264-8 |author1=National Research Council (US) Committee on the Scientific Basis for Predicting the Invasive Potential of Nonindigenous Plants Plant Pests in the United States |title=Predicting Invasions of Nonindigenous Plants and Plant Pests |access-date=November 17, 2019 |archive-date=November 17, 2019 |archive-url=https://web.archive.org/web/20191117204337/https://www.nap.edu/read/10259/chapter/1 |url-status=live}}</ref><ref>{{cite journal |doi=10.1038/nature14258 |title=Defining the Anthropocene |year=2015 |last1=Lewis |first1=Simon L. |last2=Maslin |first2=Mark A. |s2cid=205242896 |journal=[[Nature (journal) |Nature]] |volume=519 |issue=7542 |pages=171–180 |pmid=25762280 |bibcode=2015Natur.519..171L}}</ref> This may be particularly true in inadequately regulated [[fresh water]] systems, though [[quarantine]]s and [[ballast water]] rules have improved the situation.<ref>{{cite web |url=http://www.millenniumassessment.org/documents/document.354.aspx.pdf |title=Ecosystems and Human Well-being: Biodiversity Synthesis |author=Millennium Ecosystem Assessment |year=2005 |publisher=[[World Resources Institute]] |author-link=Millennium Ecosystem Assessment |access-date=September 18, 2007 |archive-date=October 14, 2019 |archive-url=https://web.archive.org/web/20191014033601/http://www.millenniumassessment.org/documents/document.354.aspx.pdf |url-status=live}}</ref>

[[File:Gator and Python.jpg |thumb |right |[[American alligator]] combatting a [[Burmese python in Florida |Burmese python]] in Florida ]]

Invasive species may drive local native species to extinction via [[Competition (biology) |competitive]] exclusion, [[Ecological niche |niche]] displacement, or [[hybrid (biology) |hybrid]]isation with related native species. Therefore, besides their economic ramifications, alien invasions may result in extensive changes in the structure, composition and global distribution of the biota at sites of introduction, leading ultimately to the homogenisation of the world's fauna and flora and the [[loss of biodiversity]].<ref>{{cite journal |doi=10.1098/rspb.2012.1651 |title=Pattern and process of biotic homogenization in the New Pangaea |year=2012 |last1=Baiser |first1=Benjamin |last2=Olden |first2=Julian D. |last3=Record |first3=Sydne |last4=Lockwood |first4=Julie L. |last5=McKinney |first5=Michael L. |journal=[[Proceedings of the Royal Society B: Biological Sciences]] |volume=279 |issue=1748 |pages=4772–4777 |pmid=23055062 |pmc=3497087}}</ref><ref name="Odendaal 2008">{{cite journal |last1=Odendaal |first1=L. J. |last2=Haupt |first2=T. M. |last3=Griffiths |first3=C. L. |year=2008 |title=The alien invasive land snail ''Theba pisana'' in the West Coast National Park: Is there cause for concern? |journal=[[Koedoe]] |volume=50 |issue=1 |pages=93–98 |doi=10.4102/koedoe.v50i1.153 |doi-access=free }}</ref> It is difficult to unequivocally attribute extinctions to a species invasion, though there is for example strong evidence that the extinction of about 90 amphibian species was caused by the [[chytridiomycosis|chytrid fungus]] spread by international trade.<ref>{{cite journal |doi=10.1038/s41579-020-0335-x |title=Chytrid fungi and global amphibian declines |year=2020 |last1=Fisher |first1=Matthew C. |last2=Garner |first2=Trenton W. J. |s2cid=211266075 |journal=[[Nature Reviews Microbiology]] |volume=18 |issue=6 |pages=332–343 |pmid=32099078 |url=https://discovery.ucl.ac.uk/id/eprint/10092667/1/NRMICRO-19-244_FINAL_ACCEPTED.pdf |hdl=10044/1/78596 |hdl-access=free |access-date=September 28, 2020 |archive-date=November 7, 2020 |archive-url=https://web.archive.org/web/20201107202307/https://discovery.ucl.ac.uk/id/eprint/10092667/1/NRMICRO-19-244_FINAL_ACCEPTED.pdf |url-status=live}}</ref>

Multiple successive introductions of different non-native species can worsen the total effect, as with the introductions of the [[amethyst gem clam]] and the [[Carcinus maenas|European green crab]]. The gem clam was introduced into California's [[Bodega Bay|Bodega Harbor]] from the US East Coast a century ago. On its own, it never displaced native clams (''Nutricola'' spp.). In the mid-1990s, the introduction of the European green crab resulted in an increase of the amethyst gem at the expense of the native clams.<ref>{{cite journal |last=Grosholz |first=E.D. |year=2005 |title=Recent biological invasion may hasten invasional meltdown by accelerating historical introductions |journal=[[Proceedings of the National Academy of Sciences]] |volume=102 |pages=1088–1091 |doi=10.1073/pnas.0308547102 |pmid=15657121 |issue=4 |pmc=545825 |bibcode=2005PNAS..102.1088G |doi-access=free }}</ref> In India, multiple invasive plants  have invaded 66% of natural areas, reducing the densities of native forage plants, declining the habitat-use by wild herbivores and threatening the long-term sustenance of dependent carnivores, including the [[tiger]].<ref>{{Cite journal |last=Mungi |first=Ninad Avinash |title=Distribution, drivers and restoration priorities of plant invasions in India |journal=Journal of Applied Ecology |date=2023 |volume=60 |issue=11 |pages=2400–2412|doi=10.1111/1365-2664.14506 |bibcode=2023JApEc..60.2400M |doi-access=free }}</ref><ref>{{Cite journal |last=Rastogi |first=Rajat |title=Multiple invasions exert combined magnified effects on native plants, soil nutrients and alters the plant-herbivore interaction in dry tropical forest |url=https://www.sciencedirect.com/science/article/pii/S0378112723000142 |journal=Forest Ecology and Management |date=2023 |volume=531 |pages=120781|doi=10.1016/j.foreco.2023.120781 |bibcode=2023ForEM.53120781R }}</ref>

Invasive species can change the functions of ecosystems. For example, invasive plants can alter the [[fire regime]] (cheatgrass, ''[[Drooping Brome |Bromus tectorum]]''), [[nutrient cycling]] (smooth cordgrass ''[[Spartina alterniflora]]''), and hydrology (''[[Tamarix]]'') in native ecosystems.<ref name = causesepidemiology /> Invasive species that are closely related to rare native species have the potential to hybridize with the native species. Harmful effects of hybridization have led to a decline and even extinction of native species.<ref>{{cite journal |last=Hawkes |first=C.V. |year=2005 |title=Plant invasion alters nitrogen cycling by modifying the soil nitrifying community |journal=[[Ecology Letters]] |volume=8 |pages=976–985 |doi=10.1111/j.1461-0248.2005.00802.x |issue=9 |pmid=34517683 |bibcode=2005EcolL...8..976H }}</ref><ref name="rhymer">{{cite journal |last=Rhymer |first=J. M. |author2=Simberloff, D. |year=1996 |title=Extinction by hybridization and introgression |journal=[[Annual Review of Ecology and Systematics]] |issue=1 |pages=83–109 |doi=10.1146/annurev.ecolsys.27.1.83 |volume=27|bibcode=1996AnRES..27...83R }}</ref> For example, [[Hybridization (biology) |hybridization]] with introduced cordgrass, ''Spartina alterniflora'', threatens the existence of California cordgrass (''[[Spartina foliosa]]'') in [[San Francisco Bay]].<ref name="ayres">{{cite journal |last=Ayres |first=D. |s2cid=24732543 |year=2004 |title=Spread of exotic cordgrasses and hybrids (''Spartina'' sp.) in the tidal marshes of San Francisco Bay, California, USA |journal=[[Biological Invasions]] |volume=6 |pages=221–231 |doi=10.1023/B:BINV.0000022140.07404.b7 |issue=2 |bibcode=2004BiInv...6..221A |display-authors=etal}}</ref> Invasive species cause competition for native species and because of this 400 of the 958 endangered species under the [[Endangered Species Act of 1973 |Endangered Species Act]] are at risk.<ref>{{cite journal |last=Primtel |first=David |year=2005 |title=Update on the environmental and economic costs associated with alien-invasive species in the United States |journal=[[Ecological Economics (journal) |Ecological Economics]] |volume=52 |issue=3 |pages=273–288 |doi=10.1016/j.ecolecon.2004.10.002|bibcode=2005EcoEc..52..273P }}</ref>

[[File:Firewoodposter white web.pdf |thumb |left |Poster from the [[Government of California|State of California]] asking campers to not move firewood around, avoiding the spread of invasive species]]

The unintentional introduction of forest pest species and plant pathogens can change [[forest ecology]] and damage the [[timber industry]]. Overall, [[forest ecosystem]]s in the U.S. are widely invaded by exotic pests, plants, and pathogens.<ref>{{cite journal |last1=Liebhold |first1=S. |year=2013 |title=A highly aggregated geographical distribution of forest pest invasions in the USA |doi=10.1111/ddi.12112 |journal=[[Diversity and Distributions]] |volume=19 |issue=9 |pages=1208–1216 |s2cid=85799394 |display-authors=etal |doi-access=free |bibcode=2013DivDi..19.1208L }}</ref><ref>{{cite journal |last1=Oswalt |first1=C. |year=2015 |title=A subcontinental view of forest plant invasions |journal=[[NeoBiota]] |volume=24 |pages=49–54 |display-authors=etal |doi=10.3897/neobiota.24.8378 |doi-access=free }}</ref>

The Asian long-horned beetle (''[[Anoplophora glabripennis]]'') was first introduced into the U.S. in 1996, and was expected to infect and damage millions of acres of hardwood trees. As of 2005 thirty million dollars had been spent in attempts to eradicate this pest and protect millions of trees in the affected regions.<ref name="pimental"/> The [[woolly adelgid]] has inflicted damage on old-growth spruce, fir and [[Tsuga |hemlock]] forests and damages the [[Christmas tree]] industry.<ref>{{Cite web |title=South/Adelges piceae - Bugwoodwiki |url=https://wiki.bugwood.org/Archive:South/Balsam_Woolly_Aphid |url-status=live |archive-url=https://web.archive.org/web/20110722063118/http://wiki.bugwood.org/Archive:South/Balsam_Woolly_Aphid |archive-date=22 July 2011 |access-date=2022-06-26 |website=wiki.bugwood.org}}</ref>  [[Chestnut blight]] and [[Dutch elm disease]] are plant pathogens with serious impacts.<ref>Schlarbaum, Scott E., Frederick Hebard, Pauline C. Spaine, and Joseph C. Kamalay. (1998) [https://www.fs.usda.gov/treesearch/pubs/745 "Three American Tragedies: Chestnut Blight, Butternut Canker, and Dutch Elm Disease'] {{Webarchive |url=https://web.archive.org/web/20200113231820/https://www.fs.usda.gov/treesearch/pubs/745 |date=January 13, 2020 }}. In: Britton, Kerry O., Ed. Exotic Pests of Eastern Forests Conference Proceedings; 1997 April 8–10; Nashville, TN. U.S. Forest Service and Tennessee Exotic Pest Plant Council., pp. 45–54.</ref><ref name="USDA-Forest Service-Schlarbaum-1997">{{cite web |author1=Schlarbaum, Scott E. |author2=Hebard, Frederick |author3=Spaine, Pauline C. |author4=Kamalay, Joseph C. |url=http://www.srs.fs.usda.gov/pubs/ja/ja_schlarbaum002.htm |title=Three American Tragedies: Chestnut Blight, Butternut Canker and Dutch Elm Disease |publisher=Southern Research Station, [[United States Forest Service |Forest Service]], [[United States Department of Agriculture]] |year=1997 |work=(originally published via: Proceedings: Exotic Pests of Eastern Forests; (1997 April 8–10); Nashville, TN. Tennessee Exotic Pest Plant Council: 45–54.) |access-date=June 22, 2012 |archive-date=April 24, 2012 |archive-url=https://web.archive.org/web/20120424101943/http://www.srs.fs.usda.gov/pubs/ja/ja_schlarbaum002.htm |url-status=live }} <br />
Alternative link and additional publication citation information: Tree Search, US Forest Service, USDA. [http://www.treesearch.fs.fed.us/pubs/745 http://www.treesearch.fs.fed.us/pubs/745] {{Webarchive |url=https://web.archive.org/web/20121123093613/http://www.treesearch.fs.fed.us/pubs/745 |date=November 23, 2012 }}</ref> Garlic mustard, ''[[Alliaria petiolata]]'', is one of the most problematic invasive plant species in eastern North American forests, where it is highly invasive of the [[understory]], reducing the growth rate of tree seedlings and threatening to modify the forest's tree composition.<ref>{{cite journal |last1=Rodger |first1=Vikki |last2=Stinson |first2=Kristin |last3=Finzi |first3=Adrian |year=2008 |title=Ready or Not, Garlic Mustard Is Moving In: ''Alliaria petiolata'' as a Member of Eastern North American Forests |doi=10.1641/b580510 |journal=[[BioScience]] |volume=58 |issue=5 |page=5 |doi-access=free }}</ref>

Native [[species]] can be threatened with [[extinction]]<ref name=":1">{{cite journal |pmc=33232 |title=The evolutionary impact of invasive species |year=2001 |volume=98 |issue=10 |pmid=11344292 |last1=Mooney |first1=HA |last2=Cleland |first2=EE |pages=5446–51 |doi=10.1073/pnas.091093398 |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |bibcode=2001PNAS...98.5446M |doi-access=free }}</ref> through the process of [[genetic pollution]]. Genetic pollution is unintentional [[Hybrid (biology) |hybridization]] and [[introgression]], which leads to homogenization or replacement of local [[genotypes]] as a result of either a numerical or [[Fitness (biology) |fitness]] advantage of the introduced species.<ref>{{cite web |url=http://www.nativeseednetwork.org/article_view?id=13 |title=Glossary: definitions from the following publication: Aubry, C., R. Shoal and V. Erickson. 2005. Grass cultivars: their origins, development, and use on national forests and grasslands in the Pacific Northwest. USDA Forest Service. 44 pages, plus appendices.; Native Seed Network (NSN), Institute for Applied Ecology, 563 SW Jefferson Ave, Corvallis, OR 97333, USA |publisher=Nativeseednetwork.org |access-date=May 17, 2011 |archive-url=https://web.archive.org/web/20060222092651/http://www.nativeseednetwork.org/article_view?id=13 |archive-date=February 22, 2006 }}</ref> Genetic pollution occurs either through introduction or through habitat modification, where previously isolated species are brought into contact with the new genotypes. Invading species have been shown to adapt to their new environments in a remarkably short amount of time.<ref name=":1"/> The population size of invading species may remain small for a number of years and then experience an explosion in population, a phenomenon known as "the lag effect".<ref name = causesepidemiology >{{cite journal |last1=Mack |first1=Richard N. |last2=Simberloff |first2=Daniel |author2-link=Daniel Simberloff |last3=Mark Lonsdale |first3=W. |last4=Evans |first4=Harry |last5=Clout |first5=Michael |last6=Bazzaz |first6=Fakhri A. |title=Biotic Invasions: Causes, Epidemiology, Global Consequences, and Control |journal=Ecological Applications |date=June 2000 |volume=10 |issue=3 |pages=689–710 |doi=10.1890/1051-0761(2000)010[0689:BICEGC]2.0.CO;2 |s2cid=711038 }}</ref>

[[File:Linepithema Argentine ant.jpg|thumb|[[Argentine ant]]s, which form [[Ant supercolony|supercolonies]] across continents, are ranked among the [[100 of the World's Worst Invasive Alien Species|world's 100&nbsp;worst invasive animal species]].<ref>{{cite report
 |last1=Boudjelas |first1=Souyad
 |year=2000
 |title=100 of the world's worst invasive alien species
 |website=iucn.org
 |publisher=[[International Union for Conservation of Nature]]
 |url=https://portals.iucn.org/library/sites/library/files/documents/2000-126.pdf
 |access-date=20 July 2018
}}
</ref>]]
Hybrids resulting from invasive species interbreeding with native species can incorporate their genotypes into the gene pool over time through [[introgression]]. Similarly, in some instances a small invading population can threaten much larger native populations. For example, ''[[Spartina alterniflora]]'' was introduced in the San Francisco Bay and hybridized with native ''[[Spartina foliosa]].'' The higher pollen count and male fitness of the invading species resulted in [[introgression]] that threatened the native populations due to lower pollen counts and lower viability of the native species.<ref>{{cite journal |title=Reciprocal hybrid formation of Spartina in San Francisco Bay |journal=[[Molecular Ecology]] |volume=9 |issue=6 |pages=765–770 |doi=10.1046/j.1365-294x.2000.00935.x |pmid=10849292 |year=2000 |last1=Anttila |first1=C. K. |last2=King |first2=R. A. |last3=Ferris |first3=C. |last4=Ayres |first4=D. R. |last5=Strong |first5=D. R. |bibcode=2000MolEc...9..765A |s2cid=32865913}}</ref> Reduction in fitness is not always apparent from [[Morphology (biology) |morphological]] observations alone. Some degree of [[gene flow]] is normal, and preserves constellations of [[gene]]s and genotypes.<ref name="rhymer"/><ref>{{Cite book |url=http://www.rirdc.gov.au/reports/AFT/01-114.pdf |title=Genetic Pollution from Farm Forestry using eucalypt species and hybrids; A report for the RIRDC/L&WA/FWPRDC]; Joint Venture Agroforestry Program; by Brad M. Potts, Robert C. Barbour, Andrew B. Hingston; September 2001; RIRDC Publication No 01/114; RIRDC Project No CPF – 3A; |year=2001 |isbn=978-0-642-58336-9 |publisher=Australian Government, Rural Industrial Research and Development Corporation |access-date=April 22, 2017 |archive-url=https://web.archive.org/web/20040102175403/http://www.rirdc.gov.au/reports/AFT/01-114.pdf |archive-date=January 2, 2004 }}</ref> An example of this is the interbreeding of migrating [[coyote]]s with the [[red wolf]], in areas of eastern [[North Carolina]] where the [[red wolf]] was reintroduced, reducing red wolf numbers.<ref>{{cite journal |doi=10.1016/j.biocon.2015.01.013 |title=Factors influencing red wolf–coyote hybridization in eastern North Carolina, USA |journal=[[Biological Conservation]] |volume=184 |pages=108–116 |year=2015 |last1=Bohling |first1=Justin H. |last2=Waits |first2=Lisette P.|bibcode=2015BCons.184..108B }}</ref>

=== Environmental ===
In South Africa's Cape Town region, analysis demonstrated that the restoration of priority source water sub-catchments through the removal of thirsty alien plant invasions (such as Australian acacias, pines and eucalyptus, and Australian black wattle) would generate expected annual water gains of 50 billion liters within 5 years compared to the business-as-usual scenario (which is important as Cape Town experiences significant [[water scarcity]]). This is the equivalent to one-sixth of the city's current supply needs. These annual gains will double within 30 years. The catchment restoration is significantly more cost-effective then other water augmentation solutions (1/10 the unit cost of alternative options).<ref>{{Cite web |title=Cape Town is Facing Day Zero |url=https://www.nature.org/en-us/about-us/where-we-work/africa/stories-in-africa/cape-town-faces--day-zero-/ |access-date=2023-11-06 |website=The Nature Conservancy}}</ref> A water fund has been established, and these exotic species are being eradicated.<ref>{{Cite web |url=https://www.nature.org/content/dam/tnc/nature/en/documents/GCTWF-summary-11.14.18.pdf |title=Greater cape town water fund |access-date=November 16, 2020 |archive-date=February 28, 2021 |archive-url=https://web.archive.org/web/20210228175854/https://www.nature.org/content/dam/tnc/nature/en/documents/GCTWF-summary-11.14.18.pdf |url-status=live}}</ref>

=== Human health ===
Invasive species can affect human health. With the alteration in ecosystem functionality (due to homogenization of biota communities), invasive species have resulted in negative effects on human well-being, which includes reduced resource availability, unrestrained spread of human diseases, recreational and educational activities, and tourism.<ref name=":8">{{cite journal |last1=Mazza |first1=G. |last2=Tricarico |first2=E. |last3=Genovesi |first3=P. |last4=Gherardi |first4=F. |title=Biological invaders are threats to human health: an overview |journal=Ethology Ecology & Evolution |volume=26 |issue=2–3 |date=2013-12-19 |doi=10.1080/03949370.2013.863225 |pages=112–129|s2cid=58888740 }}</ref><ref name=":22">{{Cite journal |last1=Pyšek |first1=P. |last2=Richardson |first2=D.M. |date=2010 |title=Invasive Species, Environmental Change and Management, and Health |journal=Annual Review of Environment and Resources |volume=35 |issue=1 |pages=25–55 |doi=10.1146/annurev-environ-033009-095548 |doi-access=free}}</ref> Alien species have caused diseases including [[HIV|human immunodeficiency virus]] (HIV), [[Monkeypox|monkey pox]], and [[severe acute respiratory syndrome]] (SARS).<ref name=":22"/>

Invasive species and accompanying control efforts can have long term [[public health]] implications. For instance, [[pesticide]]s applied to treat a particular pest species could pollute soil and surface water.<ref name="pimental"/> Encroachment of humans into previously remote ecosystems has exposed exotic diseases such as [[HIV]] to the wider population.<ref name="pimental"/> Introduced birds (e.g. [[pigeons]]), rodents and insects (e.g. [[mosquito]], [[flea]], [[louse]] and [[tsetse fly]] pests) can serve as vectors and reservoirs of human afflictions. Throughout recorded history, epidemics of human diseases, such as [[malaria]], [[yellow fever]], [[typhus]], and [[bubonic plague]], spread via these vectors.<ref name="elton"/> A recent example of an introduced disease is the spread of the [[West Nile virus]], which killed humans, birds, mammals, and reptiles.<ref>{{cite journal |last1=Lanciotti |first1=R. S. |last2=Roehrig |first2=J. T. |last3=Deubel |first3=V. |last4=Smith |first4=J. |last5=Parker |first5=M. |last6=Steele |first6=K. |last7=Crise |first7=B. |last8=Volpe |first8=K. E. |last9=Crabtree |first9=M. B. |last10=Scherret |first10=J. H. |last11=Hall |first11=R. A. |last12=MacKenzie |first12=J. S. |last13=Cropp |first13=C. B. |last14=Panigrahy |first14=B. |last15=Ostlund |first15=E. |date=17 December 1999 |title=Origin of the West Nile Virus Responsible for an Outbreak of Encephalitis in the Northeastern United States |journal=Science |volume=286 |issue=5448 |pages=2333–2337 |doi=10.1126/science.286.5448.2333 |pmid=10600742 |last16=Schmitt |first16=B. |last17=Malkinson |first17=M. |last18=Banet |first18=C. |last19=Weissman |first19=J. |last20=Komar |first20=N. |last21=Savage |first21=H. M. |last22=Stone |first22=W. |last23=McNamara |first23=T. |last24=Gubler |first24=D. J. |display-authors=6}}</ref> The introduced [[Chinese mitten crab]]s are carriers of [[Paragonimus westermani|Asian lung fluke]].{{r|pnwaquaticinv}} Waterborne disease agents, such as [[cholera]] bacteria (''[[Vibrio cholerae]]''), and causative agents of [[harmful algal bloom]]s are often transported via ballast water.<ref>{{cite journal |last=Hallegraeff |first=G.M. |year=1998 |title=Transport of toxic dinoflagellates via ships' ballast water: Bioeconomic risk assessment and efficacy of possible ballast water management strategies |journal=[[Marine Ecology Progress Series]] |volume=168 |pages=297–309 |bibcode=1998MEPS..168..297H |doi=10.3354/meps168297 |doi-access=free}}</ref>

=== Economic ===
[[File:Pasig River Intramuros Escolta Water Hyacinths.jpg|thumb|Invasive [[water hyacinth]]s clog the [[Pasig River]] in [[Manila]], [[Philippines]] in October 2020.<ref>{{cite news |last1=Dela Cruz |first1=Raymond Carl |title=Water hyacinths ground Pasig River Ferry ops |url=https://www.pna.gov.ph/articles/1117832 |access-date=10 August 2024 |work=[[Philippine News Agency]] |date=October 7, 2020 |archive-url=https://web.archive.org/web/20231028150214/https://www.pna.gov.ph/articles/1117832 |archive-date=October 28, 2023}}</ref>]]

Globally, invasive species management and control are substantial economic burdens, with expenditures reaching approximately $1.4 trillion annually.{{r|amstutz2018}} The economic impact of invasive alien species alone was estimated to exceed $423 billion annually as of 2019. This cost has exhibited a significant increase, quadrupling every decade since 1970, underscoring the escalating financial implications of these biological invasions.<ref>{{Cite web |last=Environment |first=U. N. |date=2023-09-04 |title=Invasive Alien Species Report |url=http://www.unep.org/resources/report/invasive-alien-species-report |access-date=2024-05-29 |website=www.unep.org |language=en}}</ref>

Invasive species contribute to [[Environmental degradation|ecological degradation]], altering ecosystem functionality and reducing the services ecosystems provide. This necessitates additional expenditures to control the spread of biological invasions, mitigate further impacts, and restore affected ecosystems. For example, the damage caused by 79 invasive species between 1906 and 1991 in the United States has been estimated at US$120 billion. Similarly, in [[China]], invasive species have been reported to reduce the country's gross domestic product (GDP) by 1.36% per year.<ref name=":22" /><ref>{{cite journal |last1=Xu |first1=Haigen |last2=Ding |first2=Hui |last3=Li |first3=Mingyan |last4=Qiang |first4=Sheng |last5=Guo |first5=Jianying |last6=Han |first6=Zhengmin |last7=Huang |first7=Zongguo |last8=Sun |first8=Hongying |last9=He |first9=Shunping |last10=Wu |first10=Hairong |last11=Wan |first11=Fanghao |date=2006 |title=The distribution and economic losses of alien species invasion to China |journal=Biological Invasions |volume=8 |issue=7 |pages=1495–1500 |bibcode=2006BiInv...8.1495X |doi=10.1007/s10530-005-5841-2 |s2cid=25890246}}</ref>

The management of biological invasions can be costly. In [[Australia]], for instance, the expense to monitor, control, manage, and research invasive weed species is approximately AU$116.4 million per year, with costs directed solely to central and local government.<ref name=":22" />

While in some cases, invasive species may offer economic benefits, such as the potential for commercial forestry from invasive trees, these benefits are generally overshadowed by the substantial costs associated with biological invasions. In most cases, the [[Returns (economics)|economic returns]] from invasive species are far less than the costs they impose.<ref name=":32">{{cite journal |last1=Molnar |first1=Jennifer L |last2=Gamboa |first2=Rebecca L |last3=Revenga |first3=Carmen |last4=Spalding |first4=Mark D |date=2008 |title=Assessing the global threat of invasive species to marine biodiversity |journal=Frontiers in Ecology and the Environment |volume=6 |issue=9 |pages=485–492 |bibcode=2008FrEE....6..485M |doi=10.1890/070064 }}</ref><ref name=":22" />

==== United States ====
In the [[Great Lakes region]] the [[sea lamprey]] is an invasive species. In its original habitat, it had co-evolved as a [[Parasitism |parasite]] that did not kill its host. However, in the Great Lakes Region, it acts as a predator and can consume up to 40 pounds of fish in its 12–18 month feeding period.<ref name=":0">{{cite web |url=http://www.glfc.org/sea-lamprey.php |title=Great Lakes Fishery Commission – Sea Lamprey |website=www.glfc.org |access-date=October 24, 2017 |archive-date=October 25, 2017 |archive-url=https://web.archive.org/web/20171025023343/http://www.glfc.org/sea-lamprey.php |url-status=live}}</ref> Sea lampreys prey on all types of large fish such as [[lake trout]] and [[salmon]]. The sea lampreys' destructive effects on large fish negatively affect the fishing industry and have helped cause the collapse of the population of some species.<ref name=":0"/>

[[Economic cost]]s from invasive species can be separated into direct costs through production loss in agriculture and forestry, and management costs. Estimated damage and control costs of invasive species in the U.S. amount to more than $138&nbsp;billion annually.<ref name="pimental">{{cite journal |last1=Pimentel |first1=D. |last2=R. |first2=Zuniga |last3=Morrison |first3=D |year=2005 |title=Update on the environmental and economic costs associated with alien-invasive species in the United States |journal=[[Ecological Economics]] |volume=52 |issue=3 |pages=273–288 |doi=10.1016/j.ecolecon.2004.10.002 |bibcode=2005EcoEc..52..273P }}</ref> Economic losses can occur through loss of [[recreation]]al and [[tourism]] revenues.<ref name="simb">{{cite journal |last=Simberloff |first=D. |year=2001 |jstor=41717176 |title=Biological invasions – How are they affecting us, and what can we do about them? |journal=[[Western North American Naturalist]] |volume=61 |issue=3 |pages=308–315}}</ref> When economic costs of invasions are calculated as production loss and management costs, they are low because they do not consider environmental damage; if monetary values were assigned to the [[extinction]] of species, loss in biodiversity, and loss of [[ecosystem services]], costs from impacts of invasive species would drastically increase.<ref name="pimental"/> It is often argued that the key to invasive species management is early detection and rapid response.<ref>{{Cite book |url=https://www.doi.gov/sites/doi.gov/files/migrated/invasivespecies/upload/2008-2012-National-Invasive-Species-Management-Plan.pdf |title=2008–2012 National Invasive Species Management Plan. |publisher=National Invasive Species Council, Department of the Interior |year=2008 |location=Washington, DC. |archive-url=https://web.archive.org/web/20150929011911/https://www.doi.gov/sites/doi.gov/files/migrated/invasivespecies/upload/2008-2012-National-Invasive-Species-Management-Plan.pdf |archive-date=29 September 2015 |url-status=live}}</ref> However, early response only helps when the invasive species is not frequently reintroduced into the managed area, and the cost of response is affordable.<ref>{{Cite journal |last1=Holden |first1=Matthew H. |last2=Nyrop |first2=Jan P. |last3=Ellner |first3=Stephen P. |date=June 1, 2016 |title=The economic benefit of time-varying surveillance effort for invasive species management |journal=[[Journal of Applied Ecology]] |volume=53 |issue=3 |pages=712–721 |doi=10.1111/1365-2664.12617 |doi-access=free|bibcode=2016JApEc..53..712H }}</ref>

[[File:Parthenium smothering native flora in Biodiversity Rich Forest.jpg |thumb |''[[Parthenium hysterophorus]]'', [[Achanakmar Tiger Reserve]]]]

[[Weed]]s reduce yield in [[agriculture]]. Many weeds are accidental introductions that accompany imports of commercial seeds and plants. Introduced weeds in pastures compete with native forage plants, threaten young [[cattle]] (e.g., leafy spurge, ''[[Euphorbia virgata]]'') or are unpalatable because of [[Thorns, spines, and prickles |thorns and spines]] (e.g., [[yellow starthistle]]). Forage loss from invasive weeds on pastures amounts to nearly [[US$]]1&nbsp;billion in the U.S.<ref name="pimental"/> A decline in pollinator services and loss of fruit production has been caused by [[Western honeybee |honey bees]] infected by the invasive [[varroa mite]]. Introduced rats (''[[Rattus rattus]]'' and ''[[Rattus norvegicus |R. norvegicus]]'') have become serious pests<ref>{{cite journal |last1=Gougherty |first1=Andrew V. |last2=Davies |first2=T. Jonathan |title=Towards a phylogenetic ecology of plant pests and pathogens |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |date=8 November 2021 |volume=376 |issue=1837 |pages=20200359 |doi=10.1098/rstb.2020.0359 |pmid=34538142 |pmc=8450633 }}</ref> on farms, destroying stored grains.<ref name="pimental"/> The introduction of leaf miner flies ([[Agromyzidae]]), including the American serpentine leaf miner (''[[Liriomyza trifolii]]''), to California has caused losses in California's [[floriculture]] industry, as the larvae of these invasive species feed on ornamental plants.<ref>{{cite web |url=http://entnemdept.ufl.edu/creatures/veg/leaf/a_serpentine_leafminer.htm |title=American serpentine leafminer – Liriomyza trifolii (Burgess) |website=entnemdept.ufl.edu |access-date=November 20, 2019 |archive-date=November 25, 2019 |archive-url=https://web.archive.org/web/20191125043634/http://entnemdept.ufl.edu/Creatures/veg/leaf/a_serpentine_leafminer.htm |url-status=live}}</ref>

Invasive plant pathogens and insect vectors for plant diseases can suppress agricultural yields and harm nursery stock. [[Citrus]] greening is a [[bacterial disease]] vectored by the invasive [[Asian citrus psyllid]]. As a result, citrus is under quarantine and highly regulated in areas where the psyllid has been found.<ref name="r2">{{Cite web |title=Citrus Greening |url=http://www.clemson.edu/public/regulatory/plant_industry/invasive_exotic_programs/Pest%20Alerts/citrus_greening.html |archive-url=https://archive.today/20130616000111/http://www.clemson.edu/public/regulatory/plant_industry/invasive_exotic_programs/Pest%20Alerts/citrus_greening.html |archive-date=16 June 2013 |website=Clemson Public Service Activities - The Department of Plant Industry}}</ref>

Invasive species can impact outdoor recreation, such as fishing, [[hunting]], [[hiking]], [[wildlife viewing]], and water-based activities. They can damage environmental services including [[water quality]], plant and animal diversity, and [[species abundance]], though the extent of this is under-researched.<ref>{{cite journal |last1=Eiswerth |first1=M.E. |year=2005 |title=Input-output modeling, outdoor recreation, and the economic impacts of weeds |journal=[[Weed Science]] |volume=53 |pages=130–137 |doi=10.1614/WS-04-022R |last2=Darden |first2=Tim D. |last3=Johnson |first3=Wayne S. |last4=Agapoff |first4=Jeanmarie |last5=Harris |first5=Thomas R. |s2cid=85608607 }}</ref> Eurasian watermilfoil (''[[Myriophyllum spicatum]]'') in parts of the US, fills lakes with plants, complicating fishing and boating.<ref>{{Cite web |date=1 November 2006 |title=Eurasian Watermilfoil in the Great Lakes Region |url=http://great-lakes.net/envt/flora-fauna/invasive/milfoil.html |archive-url=https://web.archive.org/web/20080725034837/http://great-lakes.net/envt/flora-fauna/invasive/milfoil.html#overview |archive-date=25 July 2008 |website=Great Lakes Information Network}}</ref> The loud call of the introduced [[common coqui]] depresses real estate values in affected neighborhoods of [[Hawaii]].<ref>{{cite book |url=http://www.aphis.usda.gov/wildlife_damage/nwrc/symposia/invasive_symposium/content/Sin157_167_MVIS.pdf |last1=Sin |first1=Hans |last2=Radford |first2=Adam |year=2007 |chapter =Coqui frog research and management efforts in Hawaii |title=Managing Vertebrate Invasive Species: Proceedings of an International Symposium (G. W. Witmer, W. C. Pitt, K. A. Fagerstone, Eds) |publisher=USDA/APHIS/WS, National Wildlife Research Center |location=Fort Collins, Colorado |access-date=June 26, 2013 |archive-date=May 25, 2017 |archive-url=https://web.archive.org/web/20170525103353/http://www.aphis.usda.gov/wildlife_damage/nwrc/symposia/invasive_symposium/content/Sin157_167_MVIS.pdf}}</ref> The large webs of the orb-weaving spider ''[[Zygiella x-notata]]'', invasive in California, disrupts garden work.<ref>{{Cite web |title=Spider Invaders |url=https://www.kqed.org/quest/9595/spider-invaders |access-date=2020-12-13 |website=KQED |date=October 18, 2010 |archive-date=November 5, 2020 |archive-url=https://web.archive.org/web/20201105170805/https://www.kqed.org/quest/9595/spider-invaders |url-status=live}}</ref>

==== Europe ====
The overall economic cost of invasive alien species in Europe between 1960 and 2020 has been estimated at around US$140 billion (including potential costs that may or may not have actually materialised) or US$78 billion (only including observed costs known to have materialised). These estimates are very conservative. Models based on these data suggest a true ''annual'' cost of around US$140 billion in 2020.<ref>{{Cite journal |last1=Haubrock |first1=Phillip J. |last2=Turbelin |first2=Anna J. |last3=Cuthbert |first3=Ross N. |last4=Novoa |first4=Ana |last5=Taylor |first5=Nigel G. |last6=Angulo |first6=Elena |last7=Ballesteros-Mejia |first7=Liliana |last8=Bodey |first8=Thomas W. |last9=Capinha |first9=César |last10=Diagne |first10=Christophe |last11=Essl |first11=Franz |last12=Golivets |first12=Marina |last13=Kirichenko |first13=Natalia |last14=Kourantidou |first14=Melina |last15=Leroy |first15=Boris |last16=Renault |first16=David |last17=Verbrugge |first17=Laura |last18=Courchamp |first18=Franck |display-authors=6  |title=Economic costs of invasive alien species across Europe |year=2021 |journal=[[Neobiota]] |volume=67 |pages=153–190 |hdl=10138/333320 |s2cid=237460752 |hdl-access=free |doi=10.3897/neobiota.67.58196 |doi-access=free }}</ref>

{{visible anchor |Italy |'''[[Italy]]'''}} is one of the most invaded countries in [[Europe]], with an estimate of more than 3,000 alien species. The impacts of invasive alien species on the economy has been wide-ranging, from management costs, to loss of crops, to infrastructure damage. The overall economic cost of invasions to Italy between 1990 and 2020 was estimated at US$819.76 million (EUR€704.78 million). However, only 15 recorded species have more reliably estimated costs, hence the actual cost may be much larger than the aforementioned sum.<ref>{{cite journal |last1=Haubrock |first1=Phillip J. |last2=Cuthbert |first2=Ross N. |last3=Tricarico |first3=Elena |last4=Diagne |first4=Christophe |last5=Courchamp |first5=Franck |last6=Gozlan |first6=Rodolphe E. |title=The recorded economic costs of alien invasive species in Italy |journal=NeoBiota |date=29 July 2021 |volume=67 |pages=247–266 |doi=10.3897/neobiota.67.57747 |s2cid=238819772 |url=https://hal.archives-ouvertes.fr/hal-03410329/file/CostsinItaly.pdf |doi-access=free |hdl=2158/1262519 }}</ref>

{{visible anchor |France |'''[[France]]'''}} has an estimated minimum of 2,750 introduced and invasive alien species. Renault et al. (2021) obtained 1,583 cost records for 98 invasive alien species and found that they caused a conservative total cost between US$1.2 billion and 11.5 billion over the period 1993–2018. This study extrapolated costs for species invading France, but for which costs were reported only in other countries but not in France, which yielded an additional cost ranging from US$151 million to $3.03 billion. Damage costs were nearly eight times higher than management expenditure. Insects, and in particular the Asian tiger mosquito ''[[Aedes albopictus]]'' and the yellow fever mosquito ''[[Aedes aegypti |Ae. aegypti]]'', totalled very high economic costs, followed by non-graminoid terrestrial flowering and aquatic plants (''[[Ambrosia artemisiifolia]]'', ''[[Ludwigia (plant) |Ludwigia]]'' sp. and ''[[Lagarosiphon major]]''). Over 90% of alien species currently recorded in France had no costs reported in the literature, resulting in high biases in taxonomic, regional and activity sector coverages. However, no reports does not mean that there are no negative consequences and thus no costs.<ref>{{cite journal |last1=Renault |first1=David |last2=Manfrini |first2=Eléna |last3=Leroy |first3=Boris |last4=Diagne |first4=Christophe |last5=Ballesteros-Mejia |first5=Liliana |last6=Angulo |first6=Elena |last7=Courchamp |first7=Franck |title=Biological invasions in France: Alarming costs and even more alarming knowledge gaps |journal=NeoBiota |date=29 July 2021 |volume=67 |pages=191–224 |doi=10.3897/neobiota.67.59134 |s2cid=237462170 |doi-access=free }}</ref>

==Favorable effects==
The entomologist [[Chris D. Thomas]] argues that most introduced species are neutral or beneficial with respect to other species<ref>{{cite book |last=Thomas |first=Chris |author-link=Chris D. Thomas |title=Inheritors of the Earth: How Nature Is Thriving in an Age of Extinction |publisher=[[PublicAffairs]] |year=2017 |isbn=978-1610397278 |pages=}}</ref> but this is a minority opinion. The [[scientific community]] ubiquitously considers their effects on [[biodiversity]] to be negative.<ref name="doubtingthomas">{{cite journal |last=Halley |first=John |date=2019 |title=Doubting Thomas and the Love of Invasive Species |department=Book Review |journal=[[Conservation Biology (journal)|Conservation Biology]] |volume=33 |issue=6 |pages=1451–1453 |bibcode=2019ConBi..33.1451H |doi=10.1111/cobi.13413 |doi-access=free}}</ref> Others point out that that conservation and restoration projects can have fascist principles behind them.<ref>{{Cite web |last=Jr |first=Tom Zeller |date=2017-05-30 |title=The Fascist History of De-Extinction |url=https://undark.org/2017/05/30/nazis-aurochs-deextinction-mammoth/ |access-date=2025-04-27 |website=Undark Magazine |language=en-US}}</ref> Some, like environmental journalist Fred Pearce, take a more philosophical stance on certain conservation paths, claiming that those "who want to cosset nature like a delicate flower, to protect it from the threat of alien species, are the ethnic cleansers of nature, neutralizing the forces that they should be promoting."<ref>{{Cite book |last=Pearce |first=Fred |title=The New Wild: Why Invasive Species Will Be Nature's Salvation |publisher=Beacon Press |year=2015 |isbn=9780807033685}}</ref> Emma Marris points out that, the "only way to really stop life from changing is to kill it." <ref>{{Cite book |last=Marris |first=Emma |title=Wild souls: freedom and flourishing in the non-human world |date=2021 |publisher=Bloomsbury Publishing |isbn=978-1-63557-494-4 |location=New York London Oxford New Delhi Sydney}}</ref> [[Indigenous peoples|Indigenous communities]] have often incorporated introduced species, such as the [[Banana|banana tree]] to the [[Americas]], into their [[Traditional diet|traditional diets]] and kinships.<ref>{{Cite book |last=Marris |first=Emma |title=Wild souls: freedom and flourishing in the non-human world |date=2021 |publisher=Bloomsbury Publishing |isbn=978-1-63557-494-4 |location=New York London Oxford New Delhi Sydney}}</ref> 

Some invasive species can provide a suitable habitat or food source for other organisms. In areas where a native has become extinct or reached a point that it cannot be restored, non-native species can fill their role. For instance, in the US, the endangered [[Willow flycatcher|southwestern willow flycatcher]] mainly nests in the non-native [[Tamarix|tamarisk]].<ref name="potential" /> 
The introduced [[Prosopis juliflora|mesquite]] is an aggressive invasive species in India, but is the preferred nesting site of native waterbirds in small cities like [[Udaipur]] in Rajasthan.<ref>{{cite journal |last1=Mehta |first1=Kanishka |last2=Koli |first2=Vijay K. |last3=Kittur |first3=Swati |last4=Sundar |first4=K. S. Gopi |title=Can you nest where you roost? Waterbirds use different sites but similar cues to locate roosting and breeding sites in a small Indian city |journal=Urban Ecosystems |date=21 February 2024 |volume=27 |issue=4 |pages=1279–1290 |doi=10.1007/s11252-023-01454-5 |bibcode=2024UrbEc..27.1279M |s2cid=267973120 }}</ref> Similarly, [[Ridgway's rail]] has adapted to the invasive hybrid of ''[[Spartina alterniflora]]'' and ''[[Spartina foliosa]]'', which offers better cover and nesting habitat.<ref>{{Cite report |url=https://spartina.org/project_documents/revegetation_program/CLRA%20Report%202012.pdf |title=Clapper Rail Surveys for the San Francisco Estuary Invasive Spartina Project |last=McBroom |first=Jen |date=December 2012 |publisher=State Coastal Conservancy |location=Oakland, California |access-date=30 November 2020 |archive-url=https://web.archive.org/web/20170305070303/http://spartina.org/project_documents/revegetation_program/CLRA%20Report%202012.pdf |archive-date=5 March 2017 |url-status=live}}</ref> In [[Australia]], saltwater crocodiles, which had become endangered, have recovered by feeding on introduced [[feral pig]]s.<ref>{{cite news |last1=Ham |first1=Anthony |title=Pigs to the Rescue: An Invasive Species Helped Save Australia's Crocodiles |url=https://www.nytimes.com/2022/08/15/science/invasive-species-pigs-crocodiles.html |work=The New York Times |date=15 August 2022 }}</ref>

Non-native species can act as catalysts for restoration, increasing the [[heterogeneity]] and biodiversity in an ecosystem. This can create microclimates in sparse and eroded ecosystems, promoting the growth and reestablishment of native species. For example, in Kenya, [[guava]] trees in farmland are attractive to many fruit-eating birds, which drop seeds from rainforest trees as much as {{cvt|2|km}} away beneath the guavas, encouraging forest regeneration.<ref>Thompson, Ken. Where Do Camels Belong? (p. 154). Greystone Books. Kindle Edition.</ref>

Non-native species can provide ecosystem services, functioning as [[biocontrol]] agents to limit the effects of invasive agricultural pests.<ref name=potential>{{cite journal |last1=Schlaepfer |first1=Martin A. |last2=Sax |first2=Dov F. |last3=Olden |first3=Julian D. |title=The Potential Conservation Value of Non-Native Species: Conservation Value of Non-Native Species |journal=Conservation Biology |date=June 2011 |volume=25 |issue=3 |pages=428–437 |doi=10.1111/j.1523-1739.2010.01646.x |pmid=21342267 |s2cid=2947682 }}</ref> [[Depletion of oysters in the Chesapeake Bay|Asian oysters]], for example, filter [[water pollutants]] better than native oysters in [[Chesapeake Bay]].<ref>Pelton, Tom (May 26, 2006) ''[[The Baltimore Sun]]''.</ref> Some species have invaded an area so long ago that they are considered to have [[Naturalisation (biology)|naturalised]] there. For example, the bee ''[[Lasioglossum leucozonium]]'', shown by population genetic analysis to be an invasive species in North America,<ref>{{Cite journal |title=Successful Biological Invasion despite a Severe Genetic Load |journal=[[PLOS ONE]]|date=September 12, 2007 |pmc=1964518 |pmid=17848999 |volume=2 |issue=9 |doi=10.1371/journal.pone.0000868 |first1=Amro |last1=Zayed |first2=Șerban A. |last2=Constantin |first3=Laurence |last3=Packer |pages=e868 |bibcode=2007PLoSO...2..868Z |doi-access=free}}</ref> has become an important pollinator of caneberry (''[[Rubus]]'' spp.) as well as [[Cucurbitaceae|cucurbit]], [[apple trees]], and [[blueberry]] bushes.<ref>{{Cite thesis |last=Adamson |first=Nancy Lee |title=An Assessment of Non-Apis Bees as Fruit and Vegetable Crop Pollinators in Southwest Virginia |date=3 February 2011 |degree=Doctor of Philosophy in Entomology |publisher=Virginia Polytechnic Institute and State University |url=http://www.step-project.net/NPDOCS/Adamson_NL_D_2011.pdf |place=Blacksburg, Virginia |access-date=November 5, 2015 |archive-date=November 20, 2015 |archive-url=https://web.archive.org/web/20151120230411/http://www.step-project.net/NPDOCS/Adamson_NL_D_2011.pdf }}</ref> In the US, the endangered [[Euphydryas editha taylori|Taylor's checkerspot]] butterfly has come to rely on invasive [[ribwort plantain]] as the food plant for its caterpillars.<ref>Thomas, Chris D.. Inheritors of the Earth (p. 148). PublicAffairs. Kindle Edition.</ref>

Some invasions offer potential commercial benefits. For instance, [[silver carp]] and [[common carp]] can be harvested for human food and exported to markets already familiar with the product, or processed into [[pet food]]s, or [[mink]] feed. [[Water hyacinth]] can be turned into fuel by [[methane digesters]],<ref name=wolv>{{cite journal|doi=10.1007/BF02858689|title=Energy from vascular plant wastewater treatment systems|journal=[[Economic Botany]]|volume=35|issue=2|pages=224–232 |year=1981 |last1=Wolverton |first1=B. C.|last2=McDonald|first2=Rebecca C.|bibcode=1981EcBot..35..224W |s2cid=24217507}}. Cited in Duke, J. (1983) [http://www.hort.purdue.edu/newcrop/duke_energy/dukeindex.html ''Handbook of Energy Crops''] {{Webarchive|url=https://web.archive.org/web/20130212071515/http://www.hort.purdue.edu/newcrop/duke_energy/dukeindex.html |date=February 12, 2013 }}. Purdue University, Center for New Crops & Plants Products</ref> and other invasive plants can be harvested and utilized as a source of [[bioenergy]].<ref>{{cite journal |title=Biomass of invasive plant species as a potential feedstock for bioenergy production |first1=Koenraad |last1=Van Meerbeek |first2=Lise |last2=Appels |first3=Raf |last3=Dewil|first4=Annelies|last4=Calmeyn|first5=Pieter|last5=Lemmens |first6=Bart |last6=Muys |first7=Martin |last7=Hermy |date=May 1, 2015 |journal=[[Biofuels, Bioproducts and Biorefining]] |volume=9 |issue=3 |pages=273–282 |doi=10.1002/bbb.1539 |s2cid=83918875 }}</ref>

== Control, eradication, and study ==
Humans are versatile enough to remediate adverse effects of species invasions.<ref>{{cite book |isbn=978-0-8166-9329-0 |title=Making Other Worlds Possible: Performing Diverse Economies |last1=Roelvink |first1=Gerda |last2=Martin |first2=Kevin St |last3=Gibson-Graham |first3=J. K. |year=2015 |publisher=University of Minnesota Press }}</ref><ref name="root"/><ref name="Garrido">{{cite journal  |last1=Garrido-Pérez |first1=Edgardo I. |last2=Tella Ruiz |first2=David |date=2016 |title=Homo sapiens (Primates: Hominidae): ¿una especie invasora o aún peor? Un reto para potenciar la Ecología y la Biología de la conservación |url=https://www.researchgate.net/publication/317083729 |journal=Puente Biológico |volume=8 |pages=43–55}}
<br/>Translated as {{cite web |last1=Garrido-Pérez |first1=Edgardo I. |last2=Tella Ruiz |first2=David |date=2016 |title=''Homo sapiens'' (Primates: Hominidae): an invasive species or even worse? A challenge for strengthening ecology and conservation biology |via=ResearchGate |url=https://www.researchgate.net/publication/319234497 |access-date=August 19, 2020 |archive-date=June 11, 2022 |archive-url=https://web.archive.org/web/20220611120711/https://www.researchgate.net/publication/319234497_Homo_sapiens_Primates_Hominidae_an_invasive_species_or_even_worse_A_challenge_for_strengthening_ecology_and_conservation_biology_Translated_from_Spanish |url-status=live }}</ref> The public is motivated by invasive species that impact their local area.<ref>{{cite web |url=http://depts.washington.edu/oldenlab/wordpress/wp-content/uploads/2013/02/Invasive-Species-Survey_Hakam_August2016.pdf#page=8 |title=Invasive Species: Public Awareness and Education |last=Hakam |first=Lara |date=February 2013 |website=University of Washington  |access-date=September 30, 2020 |archive-date=November 5, 2021 |archive-url=https://web.archive.org/web/20211105154129/http://depts.washington.edu/oldenlab/wordpress/wp-content/uploads/2013/02/Invasive-Species-Survey_Hakam_August2016.pdf#page=8 |url-status=live }}</ref> 
The control of alien species populations is important in the conservation of biodiversity in natural ecosystem. One of the most promising methods for controlling alien species is genetic.<ref>{{cite journal |last1=Makhrov |first1=A. A. |last2=Karabanov |first2=D. P. |last3=Koduhova |first3=Yu. V. |title=Genetic methods for the control of alien species |journal=Russian Journal of Biological Invasions |date=July 2014 |volume=5 |issue=3 |pages=194–202 |doi=10.1134/S2075111714030096 |bibcode=2014RuJBI...5..194M |s2cid=256073288 }}</ref>

=== <span class="anchor" id="Cargo inspection"></span><span class="anchor" id="Quarantine"></span> Cargo inspection and quarantine ===
The original motivation was to protect against [[agricultural pest]]s while still allowing the export of agricultural products. In 1994 the first set of global standards were agreed to, including the [[Agreement on the Application of Sanitary and Phytosanitary Measures]] (SPS Agreement). These are overseen by the [[World Trade Organization]]. The [[International Maritime Organization]] oversees the International Convention for the Control and Management of Ships' Ballast Water and Sediments (the [[Ballast Water Management Convention]]). Although primarily targeted at other, more general environmental concerns, the [[Convention on Biological Diversity]] does specify some steps that its members should take to control invasive species. The CBD is the most significant international agreement on the environmental consequences of invasive species; most such measures are voluntary and unspecific.<ref name="Lodge-et-al-2016">{{cite journal |last1=Lodge |first1=David M. |last2=Simonin |first2=Paul W. |last3=Burgiel |first3=Stanley W. |last4=Keller |first4=Reuben P. |last5=Bossenbroek |first5=Jonathan M. |last6=Jerde |first6=Christopher L. |last7=Kramer |first7=Andrew M. |last8=Rutherford |first8=Edward S. |last9=Barnes |first9=Matthew A. |last10=Wittmann |first10=Marion E. |last11=Chadderton |first11=W. Lindsay |last12=Apriesnig |first12=Jenny L. |display-authors=6 |title=Risk Analysis and Bioeconomics of Invasive Species to Inform Policy and Management |journal=Annual Review of Environment and Resources |date=1 November 2016 |volume=41 |issue=1 |pages=453–488 |doi=10.1146/annurev-environ-110615-085532 |doi-access=free }}</ref>

=== Slowing spread ===
[[Firefighter]]s are becoming responsible for decontamination of their own equipment, public water equipment, and private water equipment, due to the risk of aquatic invasive species transfer.<ref name="Sea-Grant-NY">{{cite web |url=http://www.slocounty.ca.gov/Departments/Public-Works/Forms-Documents/Water-Resources/Invasive-Mussels/NY-Fire-Control-Equipment.pdf |title=Zebra Mussels and Fire Control Equipment |last=O'Neill, Jr. |first=Charles R. |date=2002 |publisher=[[National Sea Grant College Program|Sea Grant]] |place=[[SUNY College at Brockport]] |access-date=May 23, 2021 |archive-date=November 5, 2021 |archive-url=https://web.archive.org/web/20211105212840/https://www.slocounty.ca.gov/Departments/Public-Works/Forms-Documents/Water-Resources/Invasive-Mussels/NY-Fire-Control-Equipment.pdf |url-status=live }}</ref> In the United States this is especially a concern for [[wildfire suppression|wildland firefighters]] because [[quagga mussel|quagga]] and [[zebra mussel|zebra]] mussel invasion and wildfires co-occur in the American West.<ref name="wildland-firefight-NPR">{{cite web |last=Ouellet |first=Nicky |date=2017-08-23 |title=Wildland Firefighters Try to Combat Spread of Invasive Species |url=http://www.npr.org/2017/08/23/545617315/wildland-firefighters-try-to-combat-spread-of-invasive-species |access-date=2021-05-23 |archive-date=June 13, 2021 |archive-url=https://web.archive.org/web/20210613005731/https://www.npr.org/2017/08/23/545617315/wildland-firefighters-try-to-combat-spread-of-invasive-species |url-status=live |publisher=[[NPR]] |work=[[All Things Considered]] }}</ref><ref name="Montana-firefight-MtPR">{{cite news |last=Ouellet |first=Nicky |title=How Montana Is Fighting Invasive Hitchhikers On Firefighting Aircraft |website=[[Montana Public Radio]] |date=2017-07-27 |url=http://www.mtpr.org/post/how-montana-fighting-invasive-hitchhikers-firefighting-aircraft |access-date=2021-05-23 |archive-date=May 23, 2021 |archive-url=https://web.archive.org/web/20210523185157/https://www.mtpr.org/post/how-montana-fighting-invasive-hitchhikers-firefighting-aircraft |url-status=live }}</ref><ref name="NWCG">{{cite web |url=http://www.nwcg.gov/sites/default/files/publications/pms444.pdf |title=Guide to Preventing Aquatic Invasive Species Transport by Wildland Fire Operations |date=January 2017 |author=[[National Wildfire Coordinating Group]] |access-date=May 23, 2021 |archive-date=April 19, 2021 |archive-url=https://web.archive.org/web/20210419034257/https://www.nwcg.gov/sites/default/files/publications/pms444.pdf |url-status=live }}</ref><ref name="Mt-DNRC">{{cite web |url=http://dnrc.mt.gov/divisions/forestry/docs/fire-and-aviation/2018-nrcg-how-to-guide_aquatic-invasive-species_final.pdf |date=June 11, 2018 |title=Decontaminating Firefighting Equipment to Reduce the Spread of Aquatic Invasive Species |author=[[National Wildfire Coordinating Group]] |access-date=May 23, 2021 |archive-date=April 28, 2021 |archive-url=https://web.archive.org/web/20210428072947/http://dnrc.mt.gov/divisions/forestry/docs/fire-and-aviation/2018-nrcg-how-to-guide_aquatic-invasive-species_final.pdf |url-status=live }}</ref>

=== Reestablishing species ===
[[File:Takahe and chick.jpg|thumb|[[Takahē]] have bred after translocation to [[island restoration|restored islands]], like these on [[Kapiti Island]], off New Zealand.]]

[[Island restoration]] deals with the eradication of invasive species on islands. A 2019 study suggests that if eradications of invasive animals were conducted on just 169 islands, the survival prospects of 9.4% of the Earth's most highly threatened terrestrial insular vertebrates would be improved.<ref>{{cite journal |last1=Holmes |first1=Nick |date=March 27, 2019 |title=Globally important islands where eradicating invasive mammals will benefit highly threatened vertebrates |journal=[[PLOS ONE]] |volume=14 |issue=3 |pages=e0212128 |doi=10.1371/journal.pone.0212128 |pmid=30917126 |pmc=6436766 |bibcode=2019PLoSO..1412128H |doi-access=free }}</ref>

Invasive vertebrate eradication on islands aligns with United Nations [[Sustainable Development Goal 15]] and associated targets.<ref name="de WitZilliacus2020">{{cite journal |last1=de Wit |first1=Luz A. |last2=Zilliacus |first2=Kelly M. |last3=Quadri |first3=Paulo |last4=Will |first4=David |last5=Grima |first5=Nelson |last6=Spatz |first6=Dena |last7=Holmes |first7=Nick |last8=Tershy |first8=Bernie |last9=Howald |first9=Gregg R. |last10=Croll |first10=Donald A. |display-authors=6 |title=Invasive vertebrate eradications on islands as a tool for implementing global Sustainable Development Goals |journal=Environmental Conservation |date=September 2020 |volume=47 |issue=3 |pages=139–148 |doi=10.1017/S0376892920000211 |bibcode=2020EnvCo..47..139D |s2cid=221990256 |doi-access=free }}</ref><ref>{{cite web |title=Pursuing Sustainable Development for Island Communities by Removing Invasive Species |url=https://www.islandconservation.org/sustainable-development-communities-removing-invasive-species/ |publisher=Island Conservation |access-date=13 August 2020 |date=13 August 2020 |archive-date=September 26, 2020 |archive-url=https://web.archive.org/web/20200926042621/https://www.islandconservation.org/sustainable-development-communities-removing-invasive-species/ |url-status=live}}</ref>

[[Rodent]]s were carried to [[South Georgia Island |South Georgia]], an island in the southern Atlantic Ocean with no permanent inhabitants, in the 18th century by sealing and whaling ships. They soon wrought havoc on the island's bird population, eating eggs and attacking chicks. In 2018, the South Georgia Island was declared free of invasive rodents after a multi-year  extermination effort. Bird populations have rebounded, including the [[South Georgia pipit]] and [[South Georgia pintail]], both endemic to the island.<ref>{{Cite news |url=https://www.science.org/content/article/rat-begone-record-eradication-effort-rids-sub-antarctic-island-invasive-rodents |title=Rat begone: Record eradication effort rids sub-Antarctic island of invasive rodents |last=Warren |first=Matt |date=May 8, 2018 |work=Science |access-date=May 9, 2018 |archive-date=May 9, 2018 |archive-url=https://web.archive.org/web/20180509035618/http://www.sciencemag.org/news/2018/05/rat-begone-record-eradication-effort-rids-sub-antarctic-island-invasive-rodents |url-status=live}}</ref><ref>{{cite web |url=https://www.atlasobscura.com/articles/how-to-exterminate-rats-on-an-island |title=The Intrepid Rat-Sniffing Terriers of South Georgia Island |date=May 17, 2018 |author=Hester, Jessica Leight |work=[[Atlas Obscura]] |access-date=June 6, 2018 |archive-date=May 22, 2018 |archive-url=https://web.archive.org/web/20180522041931/https://www.atlasobscura.com/articles/how-to-exterminate-rats-on-an-island |url-status=live}}</ref>

=== Taxon substitution ===
[[File:Aldabra Giant Tortoise, Ile aux Aigrettes Nature Reserve, Mauritius.JPG|thumb|The [[Aldabra giant tortoise]] has helped to restore ecological equilibrium on two islets off Mauritius, including the [[Île aux Aigrettes]] (pictured). ]]

Non-native species can be introduced to fill an ecological engineering role that previously was performed by a native species now extinct. The procedure is known as taxon substitution.<ref name=potential/><ref>{{cite web |url=https://www.sciencedaily.com/releases/2011/02/110211095555.htm |title=Invasive plants can create positive ecological change |work=Science Daily |date=February 14, 2011 |quote="Invasive species could fill niches in degraded ecosystems and help restore native biodiversity...." |access-date=June 22, 2017 |archive-date=May 25, 2017 |archive-url=https://web.archive.org/web/20170525102601/https://www.sciencedaily.com/releases/2011/02/110211095555.htm |url-status=live}}</ref><ref>{{cite journal |last1=Searcy |first1=Christopher A. |last2=Rollins |first2=Hilary B. |last3=Shaffer |first3=H. Bradley |title=Ecological equivalency as a tool for endangered species management |year=2016 |journal=[[Ecological Applications]] |volume=26 |issue=1 |pages=94–103 |pmid=27039512 |doi=10.1890/14-1674 |doi-access=free|bibcode=2016EcoAp..26...94S }}</ref> On many islands, tortoise extinction has resulted in dysfunctional ecosystems with respect to seed dispersal and herbivory. On the offshore islets of [[Mauritius]], tortoises now extinct had served as the keystone herbivores. Introduction of the non-native [[Aldabra giant tortoise]]s on two islets in 2000 and 2007 has begun to restore ecological equilibrium. The introduced tortoises are dispersing seeds of several native plants and are selectively grazing invasive plant species. Grazing and browsing are expected to replace ongoing intensive manual weeding, and the introduced tortoises are already breeding.<ref>{{cite journal |last1=Hansen |first1=Dennis M. |last2=Donlan |first2=C. Josh |last3=Griffiths |first3=Christine J. |last4=Campbell |first4=Karl J. |title=Ecological history and latent conservation potential: Large and giant tortoises as a model for taxon substitutions |year=2010 |journal=[[Ecography]] |volume=33 |issue=2 |pages=272–284 |doi=10.1111/j.1600-0587.2010.06305.x |doi-access=free|bibcode=2010Ecogr..33..272H }}</ref>

=== By using them as food ===
{{further|List of edible invasive species}}

The practice of eating invasive species to reduce their populations has been explored. In 2005 Chef [[Bun Lai]] of [[Miya's]] Sushi in [[New Haven, Connecticut]] created the first menu dedicated to invasive species. At that time, half the items on the menu were conceptual because those invasive species were not yet commercially available.<ref name=r1>{{cite news |title=The Invasivore's Dilemma |url=https://www.outsideonline.com/1922351/invasivores-dilemma |access-date=May 28, 2019 |magazine=Outside |last=Jacobsen |first=Rowan |date=March 24, 2014 |archive-date=May 28, 2019 |archive-url=https://web.archive.org/web/20190528211949/https://www.outsideonline.com/1922351/invasivores-dilemma |url-status=live}}</ref> By 2013, Miya's offered invasive aquatic species such as Chesapeake [[blue catfish]], Florida [[lionfish]], Kentucky [[silver carp]], Georgia [[cannonball jellyfish]], and invasive plants such as [[Japanese knotweed]] and [[autumn olive]].<ref>{{cite journal |title=Invasive Species Menu of a World-Class Chef |journal=[[Scientific American]] |volume=309 |issue=3 |pages=40–43 |date=September 1, 2013 |last=Lai |first=Bun |doi=10.1038/scientificamerican0913-40 |pmid=24003552 |bibcode=2013SciAm.309c..40L}}</ref><ref>{{cite web |url=https://www.smithsonianmag.com/travel/indulge-invasive-species-restaurants-across-country-180957899/ |title=Bite Back Against Invasive Species at Your Next Meal |author=Billock, Jennifer |work=Smithsonian Magazine |date=February 9, 2016 |access-date=May 28, 2019 |archive-date=March 22, 2019 |archive-url=https://web.archive.org/web/20190322193509/https://www.smithsonianmag.com/travel/indulge-invasive-species-restaurants-across-country-180957899/ |url-status=live}}</ref><ref>{{cite web |url=https://www.scientificamerican.com/article/can-we-really-eat-invasive-species-into-submission/?redirect=1 |title=Can We Really Eat Invasive Species into Submission? |work=Scientific American |author=Snyder, Michael |date=May 19, 2017 |access-date=May 28, 2019 |archive-date=August 1, 2020 |archive-url=https://web.archive.org/web/20200801204428/https://www.scientificamerican.com/article/can-we-really-eat-invasive-species-into-submission/?redirect=1 |url-status=live}}</ref><ref>{{Cite news |last=Kolbert |first=Elizabeth |date=2 December 2012 |title=Alien Entrées |work=New Yorker |url=https://www.newyorker.com/magazine/2012/12/10/alien-entrees |url-status=live |access-date=13 February 2020 |archive-url=https://web.archive.org/web/20191018202041/https://www.newyorker.com/magazine/2012/12/10/alien-entrees |archive-date=18 October 2019}}</ref> [[Joe Roman]], a [[Harvard]] and [[University of Vermont]] conservation biologist and recipient of the [[Rachel Carson]] Environmental award, runs a website named "Eat The Invaders".<ref>{{Cite web |title=Bio |url=http://www.joeroman.com/new/bio/ |url-status=live |archive-url=https://web.archive.org/web/20190528213031/http://www.joeroman.com/bio/ |archive-date=28 May 2019 |access-date=2022-06-26 |website=Joe Roman |date=March 12, 2015}}</ref><ref>{{Cite web |title=Eat The Invaders — Fighting Invasive Species, One Bite At A Time! |url=http://eattheinvaders.org/ |url-status=live |archive-url=https://web.archive.org/web/20190519015542/http://eattheinvaders.org/ |archive-date=19 May 2019 |access-date=2022-06-26 |website=eattheinvaders.org}}</ref><ref name=r1/> In the 21st century, organizations including Reef Environmental Educational Foundation and the Institute for Applied Ecology have published cookbooks and recipes using invasive species as ingredients.<ref>{{cite book |author=Parks |first1=Mary |url=https://www.goodreads.com/book/show/44139470-the-green-crab-cookbook |title=The Green Crab Cookbook |last2=Thanh |first2=Thai |publisher=Green Crab R&d |year=2019 |isbn=9780578427942 |access-date=May 28, 2019 |archive-url=https://web.archive.org/web/20201004001822/https://www.goodreads.com/book/show/44139470-the-green-crab-cookbook |archive-date=October 4, 2020 |url-status=live}}</ref><ref>{{Cite web |url=https://www.reef.org/products/lionfish-cookbook-2nd-edition |title=Lionfish Cookbook 2nd Edition &#124; Reef Environmental Education Foundation |website=www.reef.org |access-date=May 28, 2019 |archive-date=May 28, 2019 |archive-url=https://web.archive.org/web/20190528212729/https://www.reef.org/products/lionfish-cookbook-2nd-edition |url-status=live}}</ref> Invasive plant species have been explored as a sustainable source of beneficial phytochemicals and edible protein.<ref>{{Cite journal |last1=Iyer |first1=Ajay |last2=Bestwick |first2=Charles S. |last3=Duncan |first3=Sylvia H. |last4=Russell |first4=Wendy R. |date=2021-02-15 |title=Invasive Plants Are a Valuable Alternate Protein Source and Can Contribute to Meeting Climate Change Targets |journal=Frontiers in Sustainable Food Systems |volume=5 |doi=10.3389/fsufs.2021.575056 |doi-access=free |hdl=2164/15875 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Iyer |first1=Ajay |last2=Guerrier |first2=Lisa |last3=Leveque |first3=Salomé |last4=Bestwick |first4=Charles S. |last5=Duncan |first5=Sylvia H. |last6=Russell |first6=Wendy R. |date=2022 |title=High throughput method development and optimised production of leaf protein concentrates with potential to support the agri-industry |url=https://link.springer.com/10.1007/s11694-021-01136-w |journal=Journal of Food Measurement and Characterization |volume=16 |issue=1 |pages=49–65 |doi=10.1007/s11694-021-01136-w |s2cid=244407388 |hdl=2164/19275 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Nuñez |first1=Martin A. |last2=Kuebbing |first2=Sara |last3=Dimarco |first3=Romina D. |last4=Simberloff |first4=Daniel |date=December 2012 |title=Invasive Species: to eat or not to eat, that is the question |url=https://conbio.onlinelibrary.wiley.com/doi/10.1111/j.1755-263X.2012.00250.x |journal=Conservation Letters |language=en |volume=5 |issue=5 |pages=334–341 |doi=10.1111/j.1755-263X.2012.00250.x |bibcode=2012ConL....5..334N |hdl=11336/198362 |hdl-access=free }}</ref>

Proponents of eating invasive organisms argue that humans have the ability to eat away any species that it has an appetite for, pointing to the many animals which humans have been able to hunt to extinction—such as the [[Caribbean monk seal]], and the [[passenger pigeon]]. They further point to the success that [[Jamaica]] has had in significantly decreasing the population of [[lionfish]] by encouraging the consumption of the fish.<ref>{{cite web |url=https://news.yahoo.com/invasive-lionfish-kings-caribbean-may-met-match-011600208.html |title=Invasive Lionfish, the Kings of the Caribbean, May Have Met Their Match |date=January 24, 2014 |work=Yahoo News |last=Conniff |first=Richard |archive-url=https://web.archive.org/web/20140127033047/https://news.yahoo.com/invasive-lionfish-kings-caribbean-may-met-match-011600208.html |archive-date=January 27, 2014}}</ref> Skeptics point out that once a foreign species has entrenched itself in a new place—such as the [[Indo-Pacific]] [[lionfish]] that has now virtually taken over the waters of the Western [[Atlantic Ocean |Atlantic]], [[Caribbean]] and [[Gulf of Mexico]]—eradication is almost impossible. Critics argue that encouraging consumption might have the unintended effect of spreading harmful species even more widely.<ref>{{cite news |url=https://www.theguardian.com/environment/world-on-a-plate/2015/feb/06/cooking-cant-solve-the-invasive-threat |title=Cooking can't solve the threat of invasive species |author=Bryce, Emma |date=February 6, 2015 |access-date=October 16, 2017 |work=[[The Guardian]] |archive-date=October 17, 2017 |archive-url=https://web.archive.org/web/20171017201839/https://www.theguardian.com/environment/world-on-a-plate/2015/feb/06/cooking-cant-solve-the-invasive-threat |url-status=live}}</ref>

===Pesticides and herbicides===
[[Pesticide]]s are commonly used to control invasives.<ref name="Goss2020">{{cite journal |last1=Goss |first1=EM |last2=Kendig |first2=AE |last3=Adhikari |first3=A |last4=Lane |first4=B |last5=Kortessis |first5=N |last6=Holt |first6=RD |last7=Clay |first7=K |last8=Harmon |first8=PF |last9=Flory |first9=SL |title=Disease in Invasive Plant Populations |journal=Annual Review of Phytopathology |date=August 2020 |volume=58 |issue=1 |pages=97–117 |doi=10.1146/annurev-phyto-010820-012757 |pmid=32516034 |s2cid=219563975 }}</ref> Herbicides used against invasive plants include [[fungal herbicide]]s.<ref name="Goss2020"/> Although the [[effective population size]] of an introduced population is [[population bottleneck|bottlenecked]], some [[genetic variation]] has been known to provide invasive plants with [[plant disease resistance|resistance against these fungal bioherbicides]].<ref name="Goss2020"/> Invasive populations of ''[[Bromus tectorum]]'' exist with resistance to ''[[Ustilago bullata]]'' used as a biocontrol, and a similar problem has been reported in ''[[Microstegium vimineum]]'' subject to ''[[Bipolaris microstegii]]'' and ''[[Bipolaris drechsleri|B. drechsleri]]''.<ref name="Goss2020"/> This is not solely a character of invasive plant genetics but is normal for wild plants such as the weed ''[[Linum marginale]]'' and its fungal pathogen ''[[Melampsora lini]]''.<ref name="Goss2020"/> Crops have another disadvantage over any uncontrolled plant – wild native or invasive – namely their greater uptake of nutrients, as they are [[crop breeding|deliberately bred]] to increase nutrient intake to enable increased product output.<ref name="Goss2020"/>

=== Gene drive ===
A [[gene drive]] could be used to eliminate invasive species and has, for example, been proposed as a way to eliminate [[invasive species in New Zealand|invasive mammal species in New Zealand]].<ref name="Kalmakoff2016">{{cite web |last=Kalmakoff |first=James |url=http://www.merlinnz.com/blog/crispr-pest-free-nz/ |title=CRISPR for pest-free NZ |date=11 October 2016 |access-date=19 October 2016 |archive-date=October 19, 2016 |archive-url=https://web.archive.org/web/20161019152322/http://www.merlinnz.com/blog/crispr-pest-free-nz/ |url-status=dead }}</ref> Briefly put, an individual of a species may have two versions of a gene, one with a desired coding outcome and one not, with offspring having a 50:50 chance of inheriting one or the other. Genetic engineering can be used to inhibit inheritance of the non-desired gene, resulting in faster propagation of the desired gene in subsequent generations.<ref name="GeneDrive" /> Gene drives for biodiversity conservation purposes are being explored as part of The Genetic Biocontrol of Invasive Rodents program because they offer the potential for reduced risk to non-target species and reduced costs when compared to traditional invasive species removal techniques.<ref>{{cite web |url=http://www.geneticbiocontrol.org/wp-content/uploads/2018/05/GBIRD-FactSheet-April-2018.pdf |title=GBIRd Fact Sheet |date=1 April 2018 |access-date=14 November 2018 }}</ref> A wider outreach network for gene drive research exists to raise awareness of the value of gene drive research for the public good.<ref name="GeneDrive">{{cite web |url=https://genedrivenetwork.org |title=Mission & Principles Statement |date=1 July 2018 |access-date=14 November 2018 }}</ref> Some scientists are concerned that the technique could wipe out species in their original native habitats.<ref>{{cite web |url=http://theconversation.com/gene-drives-could-wipe-out-whole-populations-of-pests-in-one-fell-swoop-81681 |title='Gene drives' could wipe out whole populations of pests in one fell swoop |work=The Conversation|date=August 8, 2017 }}</ref> The gene could mutate, causing unforeseen problems,<ref>{{cite web |url=http://blogs.plos.org/dnascience/2017/11/30/an-argument-against-gene-drives-to-extinguish-new-zealand-mammals-life-finds-a-way/ |title=An Argument Against Gene Drives to Extinguish New Zealand Mammals: Life Finds a Way |work=Plos blogs |date=30 November 2017 }}</ref> or hybridize with native species.<ref name="NZ gene drive risks">{{cite web |last=Campbell |first=Colin |url=https://www.odt.co.nz/opinion/risks-may-accompany-gene-drive-technology#comment-1086 |title=Risks may accompany gene drive technology |publisher=[[Otago Daily Times]] |date=17 October 2016 |access-date=19 October 2016}}</ref>

=== Predicting invasive plants ===
Accurately predicting the impacts of non-native plants can be an especially effective management option because most introductions of non-native plant species are intentional.<ref>{{cite journal |last1=Ööpik |first1=Merle |last2=Kukk |first2=Toomas |last3=Kull |first3=Kalevi |last4=Kull |first4=Tiiu |title=The importance of human mediation in species establishment: analysis of the alien flora of Estonia |journal=Boreal Environment Research |date=2008 |volume=13 |issue=Supplement A |pages=53–67 |hdl=10138/235238 |hdl-access=free }}</ref><ref>{{cite journal |last1=Lehan |first1=Nora E. |last2=Murphy |first2=Julia R. |last3=Thorburn |first3=Lukas P. |last4=Bradley |first4=Bethany A. |title=Accidental introductions are an important source of invasive plants in the continental United States |journal=American Journal of Botany |date=July 2013 |volume=100 |issue=7 |pages=1287–1293 |doi=10.3732/ajb.1300061 |pmid=23825135 }}</ref><ref>{{cite book |last1=Virtue |first1=J.G. |last2=Bennett |first2=Sarita |last3=Randall |first3=R.P. |chapter=Plant introductions in Australia: how can we resolve 'weedy' conflicts of interest?: Plant introductions in Australia: how can we resolve 'weedy' conflicts of interest? |pages=42–48 |s2cid=82300163 |editor1-last=Sindel |editor1-first=Brian Mark |editor2-last=Johnson |editor2-first=Stephen Barry |title=Weed Management: Balancing People, Planet, Profit : 14th Australian Weeds Conference : Papers & Proceedings |date=2004 |publisher=Weed Society of New South Wales |isbn=978-0-9752488-0-5 }}</ref> Weed risk assessments attempt to predict the chances that a specific plant will have negative effects in a new environment, often using a standardized questionnaire. The resulting total score is associated with a management action such as "prevent introduction".<ref name=":2">{{cite journal |last1=Pheloung |first1=P.C. |last2=Williams |first2=P.A. |last3=Halloy |first3=S.R. |title=A weed risk assessment model for use as a biosecurity tool evaluating plant introductions |journal=Journal of Environmental Management |date=December 1999 |volume=57 |issue=4 |pages=239–251 |doi=10.1006/jema.1999.0297 |bibcode=1999JEnvM..57..239P }}</ref><ref name=":3">{{cite journal |last1=Koop |first1=Anthony L. |last2=Fowler |first2=Larry |last3=Newton |first3=Leslie P. |last4=Caton |first4=Barney P. |title=Development and validation of a weed screening tool for the United States |journal=Biological Invasions |date=February 2012 |volume=14 |issue=2 |pages=273–294 |doi=10.1007/s10530-011-0061-4 |bibcode=2012BiInv..14..273K |s2cid=254280051 }}</ref> Assessments commonly use information about the physiology,<ref name=":2" /> life history,<ref name=":3" /> native ranges,<ref>{{cite journal |last1=Pfadenhauer |first1=William G. |last2=Nelson |first2=Michael F. |last3=Laginhas |first3=Brit B. |last4=Bradley |first4=Bethany A. |title=Remember your roots: Biogeographic properties of plants' native habitats can inform invasive plant risk assessments |journal=Diversity and Distributions |date=January 2023 |volume=29 |issue=1 |pages=4–18 |doi=10.1111/ddi.13639 |s2cid=253220107 |url=https://scholarworks.umass.edu/cgi/viewcontent.cgi?article=1002&context=oeb_grad_pubs |doi-access=free |bibcode=2023DivDi..29....4P }}</ref> and phylogenetic relationships of the species evaluated. The effectiveness of the approach is debated.<ref>{{cite journal |last1=Gordon |first1=Doria R. |last2=Flory |first2=S. Luke |last3=Lieurance |first3=Deah |last4=Hulme |first4=Philip E. |last5=Buddenhagen |first5=Chris |last6=Caton |first6=Barney |last7=Champion |first7=Paul D. |last8=Culley |first8=Theresa M. |last9=Daehler |first9=Curt |last10=Essl |first10=Franz |last11=Hill |first11=Jeffrey E. |last12=Keller |first12=Reuben P. |last13=Kohl |first13=Lisa |last14=Koop |first14=Anthony L. |last15=Kumschick |first15=Sabrina |last16=Lodge |first16=David M. |last17=Mack |first17=Richard N. |last18=Meyerson |first18=Laura A. |last19=Pallipparambil |first19=Godshen R. |last20=Panetta |first20=F. Dane |last21=Porter |first21=Read |last22=Pyšek |first22=Petr |last23=Quinn |first23=Lauren D. |last24=Richardson |first24=David M. |last25=Simberloff |first25=Daniel |last26=Vilà |first26=Montserrat |display-authors=6 |title=Weed Risk Assessments Are an Effective Component of Invasion Risk Management |journal=Invasive Plant Science and Management |date=March 2016 |volume=9 |issue=1 |pages=81–83 |doi=10.1614/IPSM-D-15-00053.1 |s2cid=86276601 }}</ref><ref>{{cite journal |last1=Hulme |first1=Philip E. |title=Weed risk assessment: a way forward or a waste of time?: Weed risk assessment: a way forward or waste of time? |journal=Journal of Applied Ecology |date=February 2012 |volume=49 |issue=1 |pages=10–19 |doi=10.1111/j.1365-2664.2011.02069.x |doi-access=free }}</ref>

=== Returning invasive species to origin country ===
In 2025 in the first time in history a project to return an invasive specie to the country it came from, has been started in the [[Hebrides]] in [[Scotland]]. [[Hedgehog|Hedgehogs]] "native to the UK mainland" were brought to those islands decades ago to fight garden pests, but the introduction create severe harm to birds which are nesting on the ground. The authorities decided to move them back to the mainland, meaning help to the birds but do not do harm to the hedgehogs.<ref>{{cite news |last1=Elliards |first1=Xander |title=Hedgehogs to be evicted from Scottish island in world-first trial |url=https://www.thenational.scot/news/25075393.hedgehogs-evicted-scottish-island-world-first-trial/ |access-date=10 April 2025 |agency=The National |date=9 April 2025}}</ref>

==See also==
* [[Adventive plant]]
* [[Archaeophyte]]
* [[Climate change and invasive species]]
* [[Ecologically based invasive plant management]]
* [[Escaped plant]]
* [[Hemerochory]]
* [[Invasion genetics]]
* [[Lists of invasive species]]
* [[Naturalisation (biology)]]
* [[Neophyte (botany)]]
* [[Seed dispersal]]
* [[100 of the World's Worst Invasive Alien Species]]

== References ==
=== Attribution ===
This article incorporates CC-BY-3.0 text from the reference<ref name="Odendaal 2008"/>

=== Citations ===
{{Reflist|refs=
<ref name=amstutz2018>{{Cite book|last=Amstutz|first=Lisa J|title=Invasive Species|publisher=Abdo Publishing|year=2018|isbn=9781532110245|location=Minneapolis, MN|pages=8–10}}</ref>
<ref name=davis>{{cite journal |last1=Davis |first1=Mark A. |last2=Thompson |first2=Ken |year=2000 |title=Eight Ways to be a Colonizer; Two Ways to be an Invader: A Proposed Nomenclature Scheme for Invasion Ecology |journal=Bulletin of the Ecological Society of America |volume=81 |number=3 |pages=226–230  |jstor=20168448}}</ref>
<ref name=ehrenfeld2010>{{cite journal |last1=Ehrenfeld |first1=Joan G. |title=Ecosystem Consequences of Biological Invasions |journal=Annual Review of Ecology, Evolution, and Systematics |date=1 December 2010 |volume=41 |issue=1 |pages=59–80 |doi=10.1146/annurev-ecolsys-102209-144650 }}</ref>
<ref name=ivey2019>{{cite journal |last1=Ivey |first1=Matthew R. |last2=Colvin |first2=Michael |last3=Strickland |first3=Bronson K. |last4=Lashley |first4=Marcus A. |date=June 14, 2019 |title=Reduced vertebrate diversity independent of spatial scale following feral swine invasions |journal=[[Ecology and Evolution]] |volume=9 |issue=13 |pages=7761–7767 |doi=10.1002/ece3.5360 |pmid=31346438 |pmc=6635915|bibcode=2019EcoEv...9.7761I }}</ref>
<ref name=pnwaquaticinv>Aquatic invasive species. A Guide to Least-Wanted Aquatic Organisms of the Pacific Northwest. 2001. University of Washington</ref>
<ref name=trainer2012>{{Cite journal|last1=Trainer|first1=Vera L.|last2=Bates|first2=Stephen S.|last3=Lundholm|first3=Nina|last4=Thessen|first4=Anne E.|last5=Cochlan|first5=William P.|last6=Adams|first6=Nicolaus G.|last7=Trick|first7=Charles G.|date=2012|title=Pseudo-nitzschia physiological ecology, phylogeny, toxicity, monitoring and impacts on ecosystem health|journal=Harmful Algae|volume=14|pages=271–300|doi=10.1016/j.hal.2011.10.025|bibcode=2012HAlga..14..271T |hdl=1912/5118|hdl-access=free}}</ref>
}}

== Further reading ==
* {{cite journal |last1=Mitchell |first1=Heidi J. |last2=Bartsch |first2=Detlef |title=Regulation of GM Organisms for Invasive Species Control |journal=Frontiers in Bioengineering and Biotechnology |date=21 January 2020 |volume=7 |pages=454 |doi=10.3389/fbioe.2019.00454 |pmid=32039172 |pmc=6985037 |doi-access=free }}
* [https://sitn.hms.harvard.edu/flash/2014/removing-threat-from-invasive-species-with-genetic-engineering/ Removing Threat from Invasive Species with Genetic Engineering]—''Science in the News''
* {{cite web |url=https://theconversation.com/the-true-damage-of-invasive-alien-species-was-just-revealed-in-a-landmark-report-heres-how-we-must-act-211893|title=The true damage of invasive alien species was just revealed in a landmark report. Here's how we must act|last=Sheppard|first=Andy|display-authors=etal.|date= September 4, 2023|website=[[The Conversation (website)|The Conversation]] |publisher= |access-date= |quote=}}
* White, Michael (13 Dec 2017) [6 Dec 2017]. [https://psmag.com/environment/should-we-fight-invasive-species-with-genetic-engineering "Should We Fight Invasive Species with Genetic Engineering?"]  ''Pacific Standard''.

== External links ==
* [https://www.naisn.org/ North American Invasive Species Network], a consortium that uses a coordinated network to advance science-based understanding and enhance management of non-native, invasive species.
* [https://www.nonnativespecies.org/ Great Britain Non-native Species Secretariat (NNNS) website]
* [https://www.cabi.org/ISC/ CABI Invasive Species Compendium], an encyclopaedic resource of scientific information
* [https://www.invasivespeciesinfo.gov/ Invasive Species], National Invasive Species Information Center, [[United States National Agricultural Library]]
* [https://web.archive.org/web/20110406095350/http://issg.org/database/welcome/ Invasive Species Specialist Group] – Global Invasive Species Database
* [http://www.hear.org/pier/ Pacific Island Ecosystems at Risk] project
* [http://www.invadingspecies.com/ invadingspecies.com] of the [[Ontario Ministry of Natural Resources]] and [[Ontario Federation of Anglers and Hunters]]
* [https://www.fisheriesireland.ie/what-we-do/research/research-theme-invasive-species Aquatic invasive species in Ireland], Inland Fisheries Ireland
* [http://ias.biodiversity.be/ Invasive alien species in Belgium] Belgian Forum on Invasive Species (BFIS)

{{Invasive species by country}}
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[[Category:Invasive species| ]]
[[Category:Environmental conservation]]
[[Category:Environmental terminology]]
[[Category:Forest pathology]]
[[Category:Habitat]]
[[Category:Pest control]]