Editing Invasive species (section)

=== 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>