Editing Island

{{Short description|Piece of subcontinental land surrounded by water}}
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{{Use American English|date=October 2024}}
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[[File:Hawaje-NoRedLine.jpg|alt=A satellite view of the Hawaiian islands, with the top of the image being North. There are few if any clouds, and most of the image is the seawater swirling in the wind, surrounding the islands.|thumb|upright=1.3|The [[Hawaiian Islands]], a major archipelago in the [[Pacific Ocean]]]]
An '''island''' or '''isle''' is a piece of land, distinct from a continent, completely surrounded by water. There are continental islands, which were formed by being split from a [[continent]] by [[plate tectonics]], and oceanic islands, which have never been part of a continent. Oceanic islands can be formed from [[volcano|volcanic]] activity, grow into [[atoll]]s from [[coral reef]]s, and form from [[sediment]] along shorelines, creating [[barrier island]]s. [[River island]]s can also form from sediment and debris in rivers. [[Artificial island]]s are those made by humans, including small rocky outcroppings built out of lagoons and large-scale [[land reclamation]] projects used for development.

Islands are host to diverse [[plant]] and [[animal]] life. Oceanic islands have the [[sea]] as a natural barrier to the introduction of new species, causing the species that do reach the island to evolve in isolation. Continental islands share animal and plant life with the continent they split from. Depending on how long ago the continental island formed, the life on that island may have diverged greatly from the mainland due to [[natural selection]].

Humans have lived on and traveled between islands for thousands of years at a minimum. Some islands became host to humans due to a [[land bridge]] or a continental island splitting from the mainland, or by boat travel. In the far north or south some islands are joined by seasonal or glacial ice. Today, up to 10% of the world's population lives on islands. Islands are popular targets for [[tourism]] due to their perceived natural beauty, isolation, and unique cultures.

Islands became the target of [[colonization]] by Europeans, resulting in the majority of islands in the Pacific being put under European control. [[Decolonization]] has resulted in some but not all island nations becoming [[self-governance|self-governing]], with lasting effects related to [[industrialisation]], [[invasive species]], [[nuclear weapons testing]], and [[tourism]]. Islands and [[island country|island countries]] are threatened by [[climate change]]. [[Sea level rise]] threatens to submerge nations such as [[Maldives]], the [[Marshall Islands]], and [[Tuvalu]] completely. Increases in the frequency and intensity of [[tropical cyclone]]s can cause widespread destruction of infrastructure and animal habitats. Species that live exclusively on islands are some of those most threatened by [[extinction]].

== Definition ==
{{Fuller projection with largest islands.svg|1=right{{!}}upright=1.0}}
An island is an area of land surrounded by water on all sides that is distinct from a continent.<ref name=":5" /> There is no standard of size that distinguishes islands and [[continent]]s. Continents have an accepted geological definition – they are the largest [[landmass]] of a particular [[list of tectonic plates|tectonic plate]].<ref name=":6">{{Cite web |title=Continent |url=https://education.nationalgeographic.org/resource/Continent |archive-url=https://web.archive.org/web/20190716045120/https://www.nationalgeographic.org/encyclopedia/continent/ |archive-date=July 16, 2019 |access-date=June 26, 2024 |website=education.nationalgeographic.org |language=en}}</ref> Islands can occur in any body of water, including [[lake]]s, [[river]]s, [[sea]]s.<ref name=":24">{{Cite web |title=Island |url=https://education.nationalgeographic.org/resource/island |access-date=July 13, 2024 |website=education.nationalgeographic.org |language=en}}</ref> [[Low-tide elevation]]s, areas of land that are not above the surface during a [[Tide#Characteristics|high tide]], are generally not considered islands.<ref name=":21">{{Cite book |last=Baldacchino |first=Godfrey |url=https://www.worldcat.org/oclc/70884504 |title=Bridging islands: the impact of fixed links |date=2007 |publisher=Acorn Press |isbn=978-1-894838-24-5 |location=Charlottetown, Prince Edward Island |oclc=70884504}}</ref> Islands that have been bridged or otherwise joined to a mainland with land reclamation are sometimes considered "de-islanded", but not in every case.<ref>{{Cite journal |last1=Pigou-Dennis |first1=Elizabeth |last2=Grydehøj |first2=Adam |date=2014 |title=Accidental and ideal island cities: islanding processes and urban design in Belize City and the urban archipelagos of Europe |url=https://islandstudiesjournal.scholasticahq.com/article/81626 |journal=Island Studies Journal |volume=9 |issue=2 |pages=259–276 |doi=10.24043/isj.305|doi-access=free }}</ref>

== Etymology ==
The word ''island'' derives from [[Middle English]] ''{{linktext|iland}}'', from [[Old English]] ''igland'' (from ''ig'' or ''ieg'', similarly meaning 'island' when used independently, and [[-land]] carrying its contemporary meaning. [[Old English]] ''ieg'' is actually a [[cognate]] of [[Swedish language|Swedish]] ''ö'' and [[German language|German]] ''Aue'', and more distantly related to Latin ''{{linktext|aqua}}'' (water).<ref>{{cite Q |Q131605459 |first=Don |last=Ringe |author-link=Donald Ringe |page=109 |mode=cs1}}</ref>

The spelling of the word was modified in the 15th century because of a [[false etymology]] caused by an association with the [[Old French]] loanword ''isle'', which itself comes from the [[Latin]] word ''insula''.<ref name=":5">{{cite dictionary |url=http://dictionary.reference.com/browse/Island |title=Island |access-date=March 5, 2007 |dictionary=[[Dictionary.com]] |url-status=live |archive-url=https://web.archive.org/web/20070307143713/http://dictionary.reference.com/browse/island |archive-date=March 7, 2007  }}</ref><ref>{{cite journal|last=Wedgwood|first=Hensleigh|author-link=Hensleigh Wedgwood|title=On False Etymologies|journal=Transactions of the Philological Society|url=https://babel.hathitrust.org/cgi/pt?id=uc1.b3924121;view=1up;seq=76|year=1855|issue=6|pages=66|access-date=September 22, 2018|archive-date=November 6, 2018|archive-url=https://web.archive.org/web/20181106160600/https://babel.hathitrust.org/cgi/pt?id=uc1.b3924121;view=1up;seq=76|url-status=live}}</ref> 

== Geology ==

[[File:Hawaii hotspot cross-sectional diagram.jpg|thumb|upright=1.3|alt=A diagram showing the movement of continental plates causing the growth and weathering of an island chain.|[[Cross section (geology)|Cross section]] through Earth at the Hawaii hotspot. [[Magma]] from the [[Earth's mantle|mantle]] rises into the [[lithosphere]], creating a chain of volcanoes as the lithosphere moves over the hotspot.]]

=== Formation in oceans ===
Islands often are found in [[archipelagos]] or island chains, which are collections of islands. These chains are thought to form from [[Hotspot (geology)|volcanic hotspots]], areas of the [[lithosphere]] where the [[Mantle (geology)|mantle]] is hotter than the surrounding area.<ref name=":1">{{Cite journal |last=Wilson |first=J. Tuzo |date=June 1, 1963 |title=A Possible Origin of the Hawaiian Islands |url=http://www.nrcresearchpress.com/doi/10.1139/p63-094 |journal=Canadian Journal of Physics |language=en |volume=41 |issue=6 |pages=863–870 |doi=10.1139/p63-094 |bibcode=1963CaJPh..41..863W |issn=0008-4204|url-access=subscription }}</ref><ref name=":0" /> These hotspots would give rise to [[volcanoes]] whose [[lava]] would form the rock the islands are made of.<ref name=":1" /> For some islands, the [[Plate tectonics|movement of tectonic plates]] above stationary hotspots would form islands in a linear chain, with the islands further away from the hotspot being progressively older and more [[eroded]], before disappearing under the sea entirely.<ref name=":2">{{Cite journal |last=Jones |first=Anthony T |date=1993 |title=Review of the chronology of marine terraces in the Hawaiian Archipelago |url=https://www.researchgate.net/publication/222594231 |journal=Quaternary Science Reviews |volume=12 |issue=9 |pages=811–823 |doi=10.1016/0277-3791(93)90019-I |bibcode=1993QSRv...12..811J |via=Research Gate}}</ref> An example is the [[Hawaiian Islands]],<ref name=":2" /> with the oldest island being 25 million years old, and the youngest, [[Hawaii (island)|Hawaii]], still being an [[active volcano]].<ref name=":0" /> However, not all island chains are formed this way. Some may be formed all at once by fractures in the tectonic plates themselves, simultaneously creating multiple islands. One supporting piece of evidence is that of the [[Line Islands]], which are all estimated to be 8 million years old, rather than being different ages.<ref name=":0">{{Cite journal |last1=Neall |first1=Vincent E. |last2=Trewick |first2=Steven A. |date=October 27, 2008 |title=The age and origin of the Pacific islands: a geological overview |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |language=en |volume=363 |issue=1508 |pages=3293–3308 |doi=10.1098/rstb.2008.0119 |issn=0962-8436 |pmc=2607379 |pmid=18768382}}</ref>

Other island chains form due to being separated from existing continents. The [[Japanese archipelago]] may have been separated from [[Eurasia]] due to [[seafloor spreading]], a phenomenon where new [[oceanic crust]] is formed, pushing away older crust.<ref name=":0" /> Islands sitting on the [[continental shelf]] may be called continental islands.<ref name=":24" /> Other islands, like those that make up [[New Zealand]], are what remains of continents that shrank and sunk beneath the sea.<ref name=":3">{{Cite journal |last1=Wallis |first1=Graham P. |last2=Trewick |first2=Steven A. |date=2009 |title=New Zealand phylogeography: evolution on a small continent |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2009.04294.x |journal=Molecular Ecology |language=en |volume=18 |issue=17 |pages=3548–3580 |doi=10.1111/j.1365-294X.2009.04294.x |pmid=19674312 |bibcode=2009MolEc..18.3548W |issn=0962-1083}}</ref> It was estimated that [[Zealandia]], the continent-like area of crust that New Zealand sits on, has had 93% of its original surface area submerged.<ref name=":3" />

Some islands are formed when [[coral reefs]] grow on volcanic islands that have submerged beneath the surface.<ref name=":4">{{Cite journal |last1=Nunn |first1=Patrick D. |last2=Kumar |first2=Lalit |last3=Eliot |first3=Ian |last4=McLean |first4=Roger F. |date=March 2, 2016 |title=Classifying Pacific islands |journal=Geoscience Letters |language=en |volume=3 |issue=1 |pages=7 |doi=10.1186/s40562-016-0041-8 |doi-access=free |bibcode=2016GSL.....3....7N |issn=2196-4092}}</ref> When these [[coral islands]] encircle a central [[lagoon]], the island is known as an [[atoll]].<ref>{{Cite web |last=Magazine |first=Smithsonian |title=Why Some Geologists Say Charles Darwin's Theory of Coral Atoll Formation Is Wrong |url=https://www.smithsonianmag.com/science-nature/why-some-geologists-say-charles-darwins-theory-coral-atoll-formation-wrong-180977052/ |access-date=July 13, 2024 |website=Smithsonian Magazine |language=en}}</ref> The formation of reefs and islands related to those reefs is aided by the buildup of sediment in shallow patches of water. In some cases, tectonic movements lifting a reef out of the water by as little as 1 meter can cause sediment to accumulate and an island to form.<ref name=":4" />

[[Barrier islands]] are long, sandy bars that form along shorelines due to the deposition of sediment by [[Wave|waves]]. These islands erode and grow as the wind and waves shift. Barrier islands have the effect of protecting coastal areas from [[Extreme weather|severe weather]] because they absorb some of the energy of large waves before they can reach the shore.<ref>{{Cite web |last=US Department of Commerce |first=National Oceanic and Atmospheric Administration |title=What is a barrier island? |url=https://oceanservice.noaa.gov/facts/barrier-islands.html |access-date=June 28, 2024 |website=oceanservice.noaa.gov |language=EN-US}}</ref>

Antarctic islands, are sometimes permanently connected to another land mass by sea or glacial ice. An example of this is [[Ross Island]] in Antarctica.

=== Formation in freshwater ===
A [[fluvial island]] is an island that forms from the [[erosion]] and [[sedimentation]] of debris in rivers; almost all rivers have some form of fluvial islands.<ref name=":7">{{Cite journal |last=Baubinienė |first=Aldona |date=December 20, 2014 |title=Formation of fluvial islands and its determining factors, case study of the River Neris, the Baltic Sea basin |url=https://d1wqtxts1xzle7.cloudfront.net/48820472/Formation_of_fluvial_islands_and_its_det20160914-14035-1xkcopo-libre.pdf?1473836921=&response-content-disposition=inline%3B+filename%3DFormation_of_fluvial_islands_and_its_det.pdf&Expires=1719430050&Signature=OvtwcmzuH~UdKFPMnT1Xqh9rXXkb41RvtDt8Cdb06gpuroNIfCDzpkcJNWqaU0JZfdYeLcbfVOof4pC52l3i7s5AmzrfbAB8GiI-8lXXj82lbdazKd6Y6p09GRV2i4sizOiiAfl3Y479MVrer-n8CQ6qEquN1tGzfLjWZv0ne6bt1f1JLWpjXWBsgNEb~B3trjUEX3XL-8q9vQ0Msrq504jT77YoDfMCP8P5AbFJrJvNal4u85CUvs88zYY~7iMFiJNiWmw9-M8SzJk1aJMGZTBpiaf2eiRTg8OJa1RYiKs2WWVXaZ1H2NB2vIfFHZXz9a-u54RMWD-C3fJhhGjOfg__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA |journal=Geomorphology |volume= 231|issue=231 |pages=343–352 |doi=10.1016/j.geomorph.2014.12.025 |bibcode=2015Geomo.231..343B |via=Elsevier Science Direct}}</ref> These islands may only be a few meters high, and are usually temporary. Changes in the flow speed, water level, and sediment content of the river may effect the rate of fluvial island formation and depletion.<ref name=":7" /> Permanent river islands also exist, the largest of which (that is completely inland) is [[Bananal Island]] in the [[Tocantins]] of Brazil, which has a maximum width of 55 kilometers.<ref>{{Cite web |title=Bananal Island {{!}} Amazon Rainforest, Wildlife & Conservation {{!}} Britannica |url=https://www.britannica.com/place/Bananal-Island |access-date=June 27, 2024 |website=www.britannica.com |language=en}}</ref>

[[Lakes]] form for a variety of reasons, including [[Glacial lake|glaciers]], plate tectonics, and volcanism.<ref>{{Cite web |title=Lake |url=https://education.nationalgeographic.org/resource/lake |access-date=June 28, 2024 |website=education.nationalgeographic.org |language=en}}</ref> [[Lake island|Lake islands]] can form as part of these processes.<ref>{{Cite web |date=May 18, 2021 |title=Largest And Highest Islands Of The World |url=https://www.worldatlas.com/geography/largest-and-highest-islands-of-the-world.html |access-date=June 28, 2024 |website=WorldAtlas |language=en-US}}</ref>

== Life on islands ==
The field of [[insular biogeography]] studies the ecological processes that take place on islands, with a focus on what factors effect the [[evolution]], [[extinction]], and [[Species richness|richness]] of species. Scientists often study islands as an isolated [[model]] of how the process of [[natural selection]] takes place.<ref>{{Cite journal |last1=Whittaker |first1=Robert J. |last2=Fernández-Palacios |first2=José María |last3=Matthews |first3=Thomas J. |last4=Borregaard |first4=Michael K. |last5=Triantis |first5=Kostas A. |date=September 2017 |title=Island biogeography: Taking the long view of nature's laboratories |url=https://www.science.org/doi/10.1126/science.aam8326 |journal=Science |language=en |volume=357 |issue=6354 |doi=10.1126/science.aam8326 |pmid=28860356 |issn=0036-8075}}</ref><ref name=":27">{{Cite journal |last1=Graham |first1=Natalie R. |last2=Gruner |first2=Daniel S. |last3=Lim |first3=Jun Y. |last4=Gillespie |first4=Rosemary G. |date=June 27, 2017 |title=Island ecology and evolution: challenges in the Anthropocene |url=https://www.cambridge.org/core/journals/environmental-conservation/article/island-ecology-and-evolution-challenges-in-the-anthropocene/ED544F1DC261A1F7B9DD9DCF1C51C9F5 |journal=Environmental Conservation |language=en |volume=44 |issue=4 |pages=323–335 |doi=10.1017/S0376892917000315 |bibcode=2017EnvCo..44..323G |issn=0376-8929}}</ref> [[Island ecology]] studies organisms on islands and their environment. It has yielded important insights for its parent field of [[ecology]] since the time of [[Charles Darwin]].<ref name=":27" />

=== Endemism ===
{{Main article|Endemism}}
[[File:Galápagos penguin (Spheniscus mendiculus) male.jpg|thumb|The [[Galapagos penguin]] is endemic to the Galápagos Islands.]]
In biology, endemism is defined as the phenomenon where species or genus is only found in a certain geographical area. Islands isolate land organisms from others with water, and isolate aquatic organisms living on them with land.<ref name=":27" /> Island ecosystems have the highest rates of endemism globally. This means that islands contribute heavily to global [[biodiversity]].<ref>{{Cite journal |last1=Veron |first1=Simon |last2=Haevermans |first2=Thomas |last3=Govaerts |first3=Rafaël |last4=Mouchet |first4=Maud |last5=Pellens |first5=Roseli |date=August 12, 2019 |title=Distribution and relative age of endemism across islands worldwide |journal=Scientific Reports |language=en |volume=9 |issue=1 |pages=11693 |doi=10.1038/s41598-019-47951-6 |pmid=31406123 |issn=2045-2322|pmc=6690940 |bibcode=2019NatSR...911693V }}</ref> Areas with high lives of biodiversity are a priority target of [[Conservation movement|conservation]] efforts, to prevent the extinction of these species.<ref>{{Cite journal |last1=Harrison |first1=Susan |last2=Noss |first2=Reed |date=January 7, 2017 |title=Endemism hotspots are linked to stable climatic refugia |journal=Annals of Botany |volume=119 |issue=2 |pages=207–214 |doi=10.1093/aob/mcw248 |issn=0305-7364 |pmc=5321063 |pmid=28064195}}</ref> Despite high levels of endemism, the total [[species richness]], the total number of unique species in a region, is lower on islands than on mainlands.<ref>{{Cite journal |last1=Kier |first1=Gerold |last2=Kreft |first2=Holger |last3=Lee |first3=Tien Ming |last4=Jetz |first4=Walter |last5=Ibisch |first5=Pierre L. |last6=Nowicki |first6=Christoph |last7=Mutke |first7=Jens |last8=Barthlott |first8=Wilhelm |date=June 9, 2009 |title=A global assessment of endemism and species richness across island and mainland regions |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=106 |issue=23 |pages=9322–9327 |doi=10.1073/pnas.0810306106 |doi-access=free |issn=0027-8424 |pmc=2685248 |pmid=19470638|bibcode=2009PNAS..106.9322K }}</ref> The level of species richness on islands is proportional to the area of that island, a phenomenon known as the [[species-area relationship]]. This is because larger areas have more resources and thus can support more organisms. Populations with a higher [[carrying capacity]] also have more [[genetic diversity]], which promotes [[speciation]].<ref name=":27" />

=== Dispersal ===
[[File:Pteropus seychellensis.jpg|alt=An orange bat hanging upside down from a tree.|thumb|The [[Seychelles fruit bat]] has a major role in distributing the seeds of trees between islands, a form of oceanic dispersal.<ref>{{Cite journal |last=Gerlach |first=Justin |date=2004 |title=The bats of Silhouette Island, Seychelles |url=https://islandbiodiversity.com/Phelsuma%2012-4.pdf |journal=Phelsuma |volume=12 |pages=78–90 |via=Nature Protection Trust of Seychelles}}</ref>]]
Oceanic islands, ones that have never been connected to shore, are only populated by life that can cross the sea. This means that any animals present on the island had to have flown there, in the case of [[birds]] or [[bats]], were carried by such animals, or were carried in a sea current in what is known as a "rafting event". This phenomenon is known as [[oceanic dispersal]].<ref name=":28">{{Cite journal |last=de Queiroz |first=Alan |date=February 2005 |title=The resurrection of oceanic dispersal in historical biogeography |url=https://www.zoology.ubc.ca/~jankowsk/deQueiroz2005.pdf |journal=[[Elsevier]] |volume=20 |issue=2 |via=Elesevier Science Direct}}</ref> [[Tropical cyclone]]s have the capacity to transport species over great distances.<ref name=":23">{{Cite web |date=October 27, 2020 |title=Intensifying hurricanes are helping invasive species spread across the U.S. |url=https://www.nationalgeographic.com/animals/article/intensifying-hurricanes-spreading-invasive-species-across-the-us |access-date=July 11, 2024 |website=Animals |language=en}}</ref> Animals like tortoises can live for weeks without food or water, and are able to survive floating on debris in the sea.<ref>{{Cite web |date=May 18, 2021 |title=How rafts helped primates rule the world |url=https://www.bbc.com/future/article/20210511-how-rafts-helped-primates-rule-the-world |access-date=July 13, 2024 |website=www.bbc.com |language=en-GB}}</ref> One case study showed that in 1995, fifteen [[iguanas]] survived a 300 km journey to [[Anguilla]] in the [[Caribbean]], an island which no iguana had lived on previously. They survived floating on a mass of uprooted trees from a storm.<ref>{{Cite journal |last1=Censky |first1=Ellen J. |last2=Hodge |first2=Karim |last3=Dudley |first3=Judy |date=1998 |title=Over-water dispersal of lizards due to hurricanes |url=https://www.nature.com/articles/26886 |journal=Nature |language=en |volume=395 |issue=6702 |pages=556 |doi=10.1038/26886 |bibcode=1998Natur.395..556C |issn=1476-4687|url-access=subscription }}</ref>  Plant species are thought to be able to travel great distances of ocean. New Zealand and Australia share 200 native plant species, despite being separated by 1500 km.<ref name=":28" />

Continental islands, islands that were at one point connected to a continent, are expected to share a common history of plant and animal life up until the point that the island broke away from the continent.<ref name=":28" /> For example, the presence of [[freshwater fish]] on an island surrounded by ocean would indicate that it once was attached to a continent, since these fish cannot traverse the ocean on their own.<ref name=":27" /> Over the course of time, evolution and extinction changes the nature of animal life on a continental island, but only once it splits from the mainland. An example is that of the [[southern beech]], a tree that is present in Australia, New Zealand, parts of South American, and New Guinea, places that today are geographically distant. A possible explanation for this phenomenon is that these landmasses were once all part of the continent [[Gondwana]] and separated by tectonic drift. However, there are competing theories that suggest this species may have reached faraway places by way of oceanic dispersal.<ref name=":28" />

=== Evolution on island groups ===
[[File:Finchadaptiveradiation.png|thumb|[[Adaptive radiation]] of finch A (''[[Geospiza magnirostris]]'') into three other species of finches on the [[Galapagos Islands]]. Due to the absence of other birds, [[Darwin's finches]] adapted to new niches. Their seed-eating beaks evolved to handle foods such as nuts, fruits, and insects.]]
Species that colonize island archipelagos exhibit a specific property known as [[adaptive radiation]]. In this process, a species that arrives on a group of islands rapidly becomes more diverse over time, splitting off into new species or subspecies. A species that reaches an island ecosystem may face little competition for resources, or may find that the resources that they found in their previous habitat are not available. These factors together result in individual evolutionary branches with different means of survival.<ref name=":29">{{Cite web |last=Lovette |first=Irby |date=December 20, 2018 |title=Why Evolution Goes Wild on Islands: The Science of Adaptive Radiation |url=https://www.allaboutbirds.org/news/why-evolution-goes-wild-on-islands-the-science-of-adaptive-radiation/ |access-date=July 13, 2024 |website=All About Birds |language=en-US}}</ref>

The classical example of this is [[Darwin's finches]], a group of up to fifteen [[tanager]] species that are endemic to the Galápagos Islands.<ref>{{Cite journal |last=Sato |first=Akie |date=March 1, 2001 |title=On the Origin of Darwin's Finches |url=https://academic.oup.com/mbe/article/18/3/299/1073209 |access-date=July 13, 2024 |journal=Molecular Biology and Evolution |volume=18 |issue=3 |pages=299–311 |doi=10.1093/oxfordjournals.molbev.a003806|pmid=11230531 }}</ref> These birds evolved different [[beaks]] in order to eat different kinds of food available on the islands. The [[large ground finch]] has a large bill used to crack seeds and eat fruit. The [[Genovesa cactus finch]] prefers [[cacti]] as a food source, and has a beak adapted for removing pulp and flowers from cacti. The [[green warbler-finch]] (in the habit of true [[warbler]] species) consumes spiders and insects that live on plants.<ref name=":29" /> Other examples of this phenomenon exist worldwide, including in Hawaii and Madagascar, and are not limited to island ecosystems.<ref name=":29" />

==== The island rule ====

[[File:Dronte dodo Raphus cucullatus.jpg|alt=A plaster and wax model of a large bird with a beak.|thumb|The extinct [[Dodo]] is an example of island gigantism.]]

Species endemic to islands show a common evolutionary trajectory. [[Foster's rule]] (also known as the island rule), states that small mammals such as [[rodents]] evolve to become larger, known as [[island gigantism]]. One such example is the [[giant tortoise]] of the [[Seychelles]], though it is unknown if it grew in size before or after reaching the island. Larger animals such as the [[hippopotamus]] tend to become smaller, such as in the case of the [[pygmy hippopotamus]]. This is known as [[insular dwarfism]].<ref name=":30">{{Cite web |last=Tyson |first=Peter |date=November 1, 2000 |title=Gigantism & Dwarfism on Islands |url=https://www.pbs.org/wgbh/nova/article/gigantism-and-dwarfism-islands/ |access-date=July 13, 2024 |website=www.pbs.org |language=en-US}}</ref> In the case of smaller animals, it has been hypothesized that animals on islands may have fewer [[predators]] and competitors, resulting in selection pressure towards larger animals. Larger animals may exhaust food resources quickly due to their size, causing [[malnutrition]] in their young, resulting in a selection pressure for smaller animals that require less food. Having fewer predators would mean these animals did not need not be large to survive.<ref name=":30" />

=== Darwin, the Galápagos, and natural selection ===
[[Charles Darwin]] formulated the theory of [[natural selection]] through the study of island ecology.<ref name=":27" /> The species he observed on the [[Galápagos Islands]], including tanager birds, contributed to his understanding of how evolution works.<ref>{{Cite web |last=MacPherson |first=Rick |date=February 6, 2017 |title=Darwin's Islands |url=https://www.americanscientist.org/article/darwins-islands |access-date=July 11, 2024 |website=American Scientist |language=en}}</ref> He first traveled to the islands as a [[naturalist]] on [[HMS Beagle]] in 1835, as part of a five-year [[circumnavigation]] of Earth. He wrote that "the different islands to a considerable extent are inhabited by a different set of beings".<ref name=":22">{{Cite web |last1=Magazine |first1=Smithsonian |last2=Helmuth |first2=Laura |title=Evolution World Tour: Galápagos Islands, Ecuador |url=https://www.smithsonianmag.com/arts-culture/evolution-world-tour-galapagos-islands-ecuador-5974755/ |access-date=July 14, 2024 |website=Smithsonian Magazine |language=en}}</ref> Through the study of the finches and other animals he realized that organisms survive by changing to adapt to their habitat.<ref name=":22" /> It would be over twenty years before he published his theories in ''[[On the Origin of Species]]''.<ref name=":31">{{Cite web |last=Stix |first=Gary |date=January 1, 2009 |title=Darwin's Living Legacy--Evolutionary Theory 150 Years Later |url=https://www.scientificamerican.com/article/darwins-living-legacy/ |access-date=July 14, 2024 |website=Scientific American |language=en}}</ref>

== Humans and islands ==

=== History of exploration ===
{{See also|Sea#Humans and the sea}}

[[File:Chronological dispersal of Austronesian people across the Pacific.svg|thumb|upright=1.3|Chronological dispersal of the [[Austronesian peoples]]<ref>{{Cite book |last1=Chambers |first1=Geoffrey K. |title=[[Encyclopedia of Life Sciences]] |year=2013 |isbn=978-0470016176 |chapter=Genetics and the Origins of the Polynesians |doi=10.1002/9780470015902.a0020808.pub2}}</ref>]]

The first evidence of humans colonizing islands probably occurred in the [[Paleolithic]] era, 100,000 to 200,000 years ago. Reaching the [[Indonesian islands]] of [[Flores]] and [[Timor]] would have required crossing distances of water of at least {{cvt|29|km}}.<ref name=":9">{{Citation |last1=Keegan |first1=William F. |title=2 - Colonization of Islands by Humans: A Biogeographical Perspective |date=January 1, 1987 |work=Advances in Archaeological Method and Theory |pages=49–92 |editor-last=Schiffer |editor-first=Michael B. |url=https://www.sciencedirect.com/science/article/pii/B9780120031108500050 |access-date=July 3, 2024 |place=San Diego |publisher=Academic Press |doi=10.1016/b978-0-12-003110-8.50005-0 |isbn=978-0-12-003110-8 |last2=Diamond |first2=Jared M.|url-access=subscription }}</ref> Some islands, such as [[Honshu]], were probably connected to the mainland with a [[land bridge]] that allowed humans to colonize it before it became an island.<ref name=":9" />

The first people to [[colonize]] distant oceanic islands were the [[Polynesians]].<ref name=":10" /> Many of the previous island settlements required traveling distances of less than {{cvt|100|km}}, whereas Polynesians may have traveled {{convert|2000|-|3200|km|mi|abbr=on}} to settle islands such as [[Tahiti]].<ref name=":9" /> They would send navigators to sail the ocean without the aid of [[navigational instruments]] to discover new islands for settlement.<ref name=":10">{{Cite web |date=February 15, 2000 |title=Polynesia's Genius Navigators |url=https://www.pbs.org/wgbh/nova/article/polynesia-genius-navigators/ |access-date=June 28, 2024 |website=www.pbs.org |language=en-US}}</ref><ref name=":20">{{Cite book |last=Gatty |first=Harold |url=https://archive.org/details/the-raft-book/page/n5/mode/2up |title=The Raft Book |publisher=George Grady Press |year=1943 |edition=2nd |location=New York City |pages=10,48,54-56}}</ref> Between 1100 and 800 BC, Polynesians sailed East from [[New Guinea]] and the [[Solomon Islands]] and reached the islands that make up the modern-day [[Fiji]] and [[Samoa]].<ref>{{Cite book |last=Lewis |first=David |url=https://books.google.com/books?id=SiCCMB6xQJoC&dq=ancient+pacific+exploration&pg=PR13 |title=We, the Navigators: The Ancient Art of Landfinding in the Pacific |date=May 1, 1994 |publisher=University of Hawaii Press |isbn=978-0-8248-1582-0 |page=8 |edition=Second |language=en}}</ref> The furthest extent of this migration would be [[Easter Island]] in the East, and [[New Zealand]] in the South, with New Zealand's first settlements between 1250 and 1300.<ref>{{Cite web |date=November 2, 2023 |title=Pacific voyaging and discovery |url=https://nzhistory.govt.nz/culture/encounters/polynesian-voyaging |access-date=June 26, 2024 |website=New Zealand History |publisher=Manatū Taonga — Ministry for Culture and Heritage}}</ref> 

Historians have sought to understand why some remote islands have always been uninhabited, while others, especially in the [[Pacific Ocean]], have long been populated by humans.<ref name=":9" /> Generally, larger islands are more likely to be able to sustain humans and thus are more likely to have been settled. Small islands that cannot sustain populations on their own can still be habitable if they are within a "commuting" distance to an island that has enough resources to be sustainable.<ref name=":9" /> The presence of an island is marked by [[seabirds]], differences in cloud and weather patterns, as well as changes in the direction of waves.<ref name=":20" /><ref name=":10" /> It is also possible for human populations to have gone extinct on islands, evidenced by explorers finding islands that show evidence of habitation but no life.<ref name=":9" />

Not all islands were or are inhabited by maritime cultures.<ref name=":9" /><ref name=":8" /> In the past, some societies were found to have lost their seafaring ability over time, such as the case of the [[Canary Islands]], which were occupied by an [[indigenous people]] since the island's first discovery in the first century until being conquered by the [[Spanish Empire]] in 1496.<ref name=":8">{{Cite journal |last=Cornwall |first=Warren |date=February 8, 2024 |title=A thousand years of solitude |url=https://www.science.org/content/article/humans-survive-alone-1000-years-desert-islands-off-africa |access-date=June 29, 2024 |journal=Science|volume=383 |issue=6683 |pages=580–584 |doi=10.1126/science.ado5092 |pmid=38330134 |bibcode=2024Sci...383..580C |url-access=subscription }}</ref> It has been hypothesized that since the inhabitants had little incentive for [[trade]] and had little to any contact with the mainland, they had no need for boats.<ref name=":8" /> 

The motivation for island exploration has been the subject of research and debate. Some early historians previously argued that early island colonization was unintentional, perhaps by a raft being swept out to sea.<ref>{{Cite journal |last1=Bird |first1=Michael I. |last2=Condie |first2=Scott A. |last3=O’Connor |first3=Sue |last4=O’Grady |first4=Damien |last5=Reepmeyer |first5=Christian |last6=Ulm |first6=Sean |last7=Zega |first7=Mojca |last8=Saltré |first8=Frédérik |last9=Bradshaw |first9=Corey J. A. |date=June 17, 2019 |title=Early human settlement of Sahul was not an accident |journal=Scientific Reports |language=en |volume=9 |issue=1 |pages=8220 |doi=10.1038/s41598-019-42946-9 |pmid=31209234 |issn=2045-2322|pmc=6579762 |bibcode=2019NatSR...9.8220B }}</ref> Others compare the motivations of Polynesian and similar explorers with those of [[Christopher Columbus]], the explorer who sailed westward over the [[Atlantic Ocean]] in search of an alternate route to the [[East Indies]].<ref name=":9" /> These historians theorize that successful explorers were rewarded with recognition and wealth, leading others to attempt possibly dangerous expeditions to discover more islands, usually with poor results.<ref name=":9" />

=== Lifestyle ===
About 10% of the world's population lives on islands.<ref name=":11">{{Cite journal |last=Ma |first=Guoqing |date=October 16, 2020 |title=Islands and the world from an anthropological perspective |journal=International Journal of Anthropology and Ethnology |language=en |volume=4 |issue=1 |pages=12 |doi=10.1186/s41257-020-00038-x |doi-access=free |issn=2366-1003}}</ref> The study of the culture of islands is known as [[island studies]]. The interest in the study of islands is due to their unique cultures and natural environments that differ from mainland cultures.<ref name=":11" /> This is for a few reasons: First, the obvious political and geographic isolation from mainland cultures.<ref name=":11" /> Second, unique restraints on resources and ecology creating marine-focused cultures with a focus on [[fishing]] and sailing.<ref name=":11" /> Third, a lasting historical and political significance of islands.<ref name=":11" />
[[File:Breadfruit (Artocarpus altilis), Malaysia.JPG|alt=Three green fruits with many small dimples hanging from a tree. It is a bright and sunny day.|thumb|A breadfruit tree in [[Malaysia]], used in Polynesia for making an edible breadfruit paste.]]
[[File:Cultivated Colocasia esculenta.jpg|alt=An orderly square of green leafy plants in the sun.|thumb|Cultivated taro plants, a [[staple food]] for many island cultures.]]

==== Diet ====
The Polynesian diet got most of its protein from fishing.<ref>{{Cite journal |last=Dewailly |first=Eric |date=2008 |title=Fish consumption and health in French Polynesia |url=https://apjcn.nhri.org.tw/server/APJCN/17/1/86.pdf |journal=Asia Pac J Clin Nutr |volume=17 |issue=1|pages=86–93 |pmid=18364332 }}</ref> Polynesians were known to fish close to shore, as well as in deep water. It was reported that [[Rapa Nui people]] were known to fish as far as {{cvt|500|km}} from shore at coral reefs.<ref name=":12">{{Cite web |date=May 8, 2024 |title=Polynesian culture - Kinship, Social Hierarchy {{!}} Britannica |url=https://www.britannica.com/place/Polynesia/Kinship-and-social-hierarchy |access-date=July 5, 2024 |website=www.britannica.com |language=en}}</ref> [[Spearfishing|Spear]], [[Fishing line|line]], and [[Fishing net|net]] fishing were all used,<ref name=":25">{{Cite web |last=Tiare Tuuhia |first=Hakai |date=November 10, 2023 |title=How an Ancient Practice Aids Marine Conservation |url=https://www.smithsonianmag.com/science-nature/rahui-and-the-art-of-marine-conservation-180983179/ |access-date=July 13, 2024 |website=Smithsonian Magazine |language=en}}</ref> to catch [[tuna]] as well as [[sharks]] and [[stingrays]].<ref name=":12" /> Island cultures also cultivate native and non-native crops.<ref name=":8" /> Polynesians grew the native [[Yam (vegetable)|yam]], [[taro]], [[breadfruit]], [[banana]], [[coconut]] and other fruits and vegetables.<ref>{{Cite book |last=Haden |first=Roger |url=https://books.google.com/books?id=sH7DEAAAQBAJ&dq=foods+grown+on+islands&pg=PP1 |title=Food Culture in the Pacific Islands |date=August 10, 2009 |publisher=Bloomsbury Publishing USA |isbn=978-0-313-34493-0 |pages=59–67 |language=en}}</ref> Different island climates made different resources more important, such as the Hawaiian islands being home to [[irrigated]] fields of taro,<ref name=":25" /> whereas in some islands, like Tahiti, breadfruit was more widely cultivated and [[fermented]] in order to preserve it.<ref>{{Cite web |title=The island fruit that caused a mutiny |url=https://www.bbc.com/travel/article/20180517-the-island-fruit-that-caused-a-mutiny |access-date=July 13, 2024 |website=www.bbc.com |language=en-GB}}</ref> There is archeological evidence that Canary Islanders would chew the roots of [[ferns]] for sustenance, a practice that wore heavily on their [[molars]].<ref name=":8" /> These islanders would also grow [[barley]] and raised livestock such as [[goats]].<ref name=":8" />

=== Island nations and territories ===
{{Further|Island country}}
Many island nations have little land and a restricted set of natural resources. However, these nations control some of the largest [[fisheries]] in the world, deposits of [[copper]], [[gold]], and [[nickel]], as well as [[Petroleum reservoir|oil deposits]]. The natural beauty of island nations also makes them a magnet for [[tourism]]. Islands also have geopolitical value for [[Naval base|naval bases]], [[Nuclear weapons testing|weapons testing]], and general territorial control. One such example is [[French Polynesia]], a territory that receives substantial military expenditure and aid from France.<ref>{{Cite book |last=Fairbairn |first=Te'o I.J. |title=The Pacific Islands: Politics, Economics, and International Relations |publisher=University of Hawaii Press |year=1991 |isbn=0-86638-140-6 |pages=1–11}}</ref> Three others, [[Palau]], [[Federated States of Micronesia]], and the [[Marshall Islands]], are island nations of the Pacific region that maintain a defense, aid, and immigration agreement with the United States called a [[Compact of Free Association]].<ref>{{Cite web |title=U.S. passes renewed Compact with Marshall Islands, other Pacific nations |url=https://www.kuaf.com/show/ozarks-at-large/2024-03-13/u-s-passes-renewed-compact-with-marshall-islands-other-pacific-nations |access-date=2025-01-31 |website=KUAF 91.3 |language=en}}</ref>

==== Colonization ====
[[File:Leaving-bikini.jpg|alt=A black and white photo of several people boarding a ship carrying their belongings.|thumb|Residents of [[Bikini Atoll]] leaving due to nuclear testing.]]
Since the first discoveries of Polynesian, [[Micronesia|Micronesian]], and other islands by Westerners, these nations have been the subject of colonization.<ref name=":14">{{Cite web |date=March 18, 2014 |title=Historical Background: Colonization of Pacific Islands |url=https://geriatrics.stanford.edu/ethnomed/hawaiian_pacific_islander/fund/historical_background/pi_colonization.html |access-date=July 8, 2024 |website=Geriatrics |language=en-US}}</ref> Islands were the target of [[Christian missionaries]]. These missionaries faced resistance, but found success when some local chiefs used European support to centralize power. Beginning in the 16th century, European states placed most of [[Oceania]] in under [[Colonialism|colonial administration]].<ref>{{Cite web |title=Australia and Oceania: Human Geography |url=https://education.nationalgeographic.org/resource/oceania-human-geography |access-date=July 13, 2024 |website=education.nationalgeographic.org |language=en}}</ref> [[Pohnpei]] was colonized by Spain as early as 1526. It changed hands from Germany to Japan to the United States before joining the [[Federated States of Micronesia]] in 1982, maintaining a "free association" status with the U.S.<ref>{{Cite journal |last1=Ragone |first1=Diane |last2=Lorence |first2=David H. |last3=Flynn |first3=Timothy |date=2001 |title=History of Plant Introductions to Pohnpei, Micronesia and the Role of the Pohnpei Agriculture Station |url=https://www.jstor.org/stable/4256429 |journal=Economic Botany |volume=55 |issue=2 |pages=290–324 |doi=10.1007/BF02864566 |jstor=4256429 |bibcode=2001EcBot..55..290R |issn=0013-0001|url-access=subscription }}</ref> [[Guam]] was a Spanish territory until 1898, and now is a [[Territories of the United States|unincorporated territory]] of the U.S.<ref>{{Cite web |last=Herman |first=Doug |date=August 15, 2017 |title=A Brief, 500-Year History of Guam |url=https://www.smithsonianmag.com/smithsonian-institution/brief-500-year-history-guam-180964508/ |access-date=July 13, 2024 |website=Smithsonian Magazine |language=en}}</ref>

The [[decolonization]] era saw many island states achieve independence or some form of [[self-governance]].<ref name=":13">{{Cite web |last=Fairbairn |first=Te'O IJ |date=1991 |title=Pacific Islands: politics, economics, and international relations |url=https://scholarspace.manoa.hawaii.edu/server/api/core/bitstreams/a858afb6-0392-4df1-bd92-cce158270479/content |access-date=July 8, 2024 |website=scholarspace.manoa.hawaii.edu |pages=15,42}}</ref> Nuclear weapons testing on the [[Marshall Islands]] left many atolls destroyed or uninhabitable, causing the [[forced displacement]] of people from their home islands as well as increases in cancer rates due to [[Effects of nuclear explosions|radiation]].<ref name=":14" /> Colonization has resulted in a decline of observance of traditional cultural practices in places such as Hawaii, where Native Hawaiians are now a minority. Cultural attitudes related to communal ownership of land as well as a lack of individualistic decision-making may make some island cultures less compatible with the global [[capitalist]] economy, causing these nations to experience less economic growth.<ref name=":13" />
[[File:Malapascua (island), Tropical beach, Philippines.jpg|alt=An idyllic beach scene with crystal clear water and tropical trees.|thumb|Tourists are attracted to tropical beaches in large numbers, such as this one in [[Malapascua]], the [[Philippines]].]]

=== Tourism ===
Islands have long been a popular target for [[tourism]], thanks to their unique climates, cultures, and natural beauty. However, islands may suffer from poor transportation connectivity from [[airplanes]] and boats and strains on infrastructure from tourist activity.<ref name=":15">{{Cite journal |last1=Brown |first1=Keith G. |last2=Cave |first2=Jenny |date=January 1, 2010 |editor-last=G. Brown |editor-first=Keith |editor2-last=Cave |editor2-first=Jenny |title=Island tourism: marketing culture and heritage – editorial introduction to the special issue |url=https://doi.org/10.1108/17506181011045163 |journal=International Journal of Culture, Tourism and Hospitality Research |volume=4 |issue=2 |pages=87–95 |doi=10.1108/17506181011045163 |issn=1750-6182|url-access=subscription }}</ref> Islands in colder climates often rely on seasonal tourists seeking to enjoy nature or local cultures, and may only be one aspect of an island's economy. In contrast, tourism on tropical islands can often make up the majority of the local economy and [[built environment]]. These islands sometimes also require consistent [[foreign aid]] on top of tourism in order to ensure economic growth. This reliance can result in [[social inequality]] and [[environmental degradation]]. During tourism downturns, these economies struggle to make up the lost inflow of cash with other industries.<ref name=":15" />

== Threats to islands ==
[[File:Calle Loíza in San Juan, Puerto Rico after Hurricane Maria.jpg|alt=A normal city street in Puerto Rico that is completely flooded in a few feet of water.|thumb|San Juan, Puerto Rico after Hurricane Maria. Climate change is expected to cause more frequent inland flooding on islands.]]{{Further|Effects of climate change on small island countries}}
[[Climate change]] threatens human development on islands due to [[sea level rise]], more dangerous [[tropical cyclones]], [[coral bleaching]], and an increase in [[invasive species]].<ref name=":16">{{Citation |title=Small Islands |date=2023 |work=Climate Change 2022 – Impacts, Adaptation and Vulnerability: Working Group II Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change |pages=2043–2122 |editor-last=Intergovernmental Panel on Climate Change (IPCC) |url=https://www.cambridge.org/core/books/climate-change-2022-impacts-adaptation-and-vulnerability/small-islands/73897C6908F3FF464B0555DC3C63DB98 |access-date=July 9, 2024 |place=Cambridge |publisher=Cambridge University Press |doi=10.1017/9781009325844.017 |isbn=978-1-009-32583-7}}</ref> For example, in 2017 [[Hurricane Maria]] caused a loss of almost all the infrastructure in Dominica. Sea level rise and other climate changes can reduce freshwater reserves, resulting in [[droughts]].<ref name=":16" /> These risks are expected to decrease the habitability of islands, especially small ones. Beyond risks to human life, plant and animal life are threatened. It has been estimated that almost 50 percent of land species threatened by [[extinction]] live on islands.<ref name=":16" /> In 2017, a detailed review of 1,288 islands found that they were home to 1,189 highly-threatened vertebrate species, which was 41 percent of the global figure.<ref name=Spatz>{{citation |author1=Spatz DR |author2=Zilliacus KM |author3=Holmes ND |author4=Butchart SHM |author5=Genovesi P |author6=Ceballos G |author7=Tershy BR |author8=Croll DA |title=Globally threatened vertebrates on islands with invasive species |journal=Science Advances |year=2017 |volume=25 |number=3 |pages=e1603080 |doi=10.1126/sciadv.1603080|pmid=29075662 |pmc=5656423 |bibcode=2017SciA....3E3080S }}</ref> Coral bleaching is expected to occur with more frequency, threatening marine ecosystems, some of which island economies are dependent on.<ref name=":16" />

Some islands that are low-lying may cease to exist given high enough amounts of sea level rise. [[Tuvalu]] received media attention for a press conference publicizing the ongoing submerging of the island country.<ref name=":17">{{Cite web |last=Prete |first=Giovanni |date=January 29, 2024 |title=Tuvalu: Why Is the Small Island Nation Sinking? |url=https://earth.org/tuvalus-sinking-reality-how-climate-change-is-threatening-a-small-island-nation/ |access-date=July 9, 2024 |website=Earth.Org |language=en}}</ref> Tuvalu signed a cooperation agreement with Australia agreeing to annually allow 280 of its citizens to become [[permanent residents]] of Australia. The Marshall Islands, a country of 1,156 islands, have also been identified as a country that may be existentially threatened by rising seas.<ref name=":17" />

Increasing intensity of tropical storms also increases the distances and frequency with which invasive species may be transported to islands. Floodwaters from these storms may also wash plants further inland than they would travel on their own, introducing them to new habitats.<ref name=":23" /> [[Agriculture]] and trade also have introduced non-native life to islands. These processes result in an introduction of [[invasive species]] to ecosystems that are especially small and fragile. One example is the [[apple snail]], initially introduced to the U.S. by [[aquarium]] owners. It has since been transported by hurricanes across the [[Gulf Coast]] and neighboring islands.<ref name=":23" /> These species compete for resources with native animals, and some may grow so densely that they displace other forms of existing life.<ref name=":23" />

== Artificial islands ==
{{Main|Artificial island}}

[[File:Kansai International Airport Aerial photograph.2007.jpg|alt=A satellite image of an artificial island in use as an airport. Several runways are visible.|thumb|[[Kansai International Airport]] in [[Osaka]] is built on an artificial island.]]

For hundreds of years, islands have been created through [[land reclamation]].<ref name=":18">{{Cite web |last1=Fisher |first1=Richard |last2=Hirschfeld |first2=Javier |date=January 6, 2022 |title=Why we are in 'the age of artificial islands' |url=https://www.bbc.com/future/article/20220105-why-were-in-the-age-of-artificial-islands |access-date=July 11, 2024 |website=www.bbc.com |language=en-GB}}</ref> One of the first recorded instances of this when people of the [[Solomon Islands]] created eighty such islands by piling coral and rock in the [[Lau Lagoon]].<ref name=":18" /> One traditional way of constructing islands is with the use of a [[revetment]]. Sandbags or stones are dropped with a barge into the sea to bring the land level slightly out of the water. The island area is then filled with sand or gravel, followed by a construction of this revetment to hold it together.<ref name=":19">{{Cite book |last1=Fang |first1=Huacan |url=https://www.sciencedirect.com/book/9780123969774/offshore-operation-facilities |title=Offshore operation facilities: equipment and procedures |last2=Duan |first2=Menglan |date=2014 |publisher=Elsevier, GPP |isbn=978-0-12-396977-4 |location=Amsterdam ; Boston |chapter=3.7.3 The Artificial Island}}</ref> Islands have also been constructed with a permanent [[Caisson (engineering)|caisson]], a steel or concrete structure built in a closed loop and then filled with sand.<ref name=":19" />

Some modern islands have been constructed by pouring millions of tons of sand into the sea, such as with [[The Pearl Island|Pearl Island]] in Qatar or the [[Palm Islands]] in Dubai.<ref name=":18" /> These islands are usually created for [[real estate development]], and are sold for private ownership or construction of housing.<ref name=":18" /> [[Oil platform|Offshore oil platforms]] have also been described as a type of island. Some atolls have been covered in concrete to create artificial islands for military purposes, such as those created by China in the [[South China Sea]].<ref name=":18" /><ref name=":26">{{Cite web |last=Mirasola |first=Christopher |date=July 15, 2015 |title=What Makes an Island? Land Reclamation and the South China Sea Arbitration |url=https://amti.csis.org/what-makes-an-island-land-reclamation-and-the-south-china-sea-arbitration/ |access-date=July 11, 2024 |website=Asia Maritime Transparency Initiative |language=en-US}}</ref> These atolls were previously low-tide elevations, landmasses that are only above water during [[low tide]]. The [[United Nations Convention on the Law of the Sea]] indicates that these islands may not have the same legal status as a naturally occurring island, and as such may not confer the same legal rights.<ref name=":26" />

== See also ==
{{Div col}}
* [[Lists of islands]]
* [[List of archipelagos]]
* [[List of artificial islands]]
* [[List of divided islands]]
* [[List of fictional islands]]
* [[List of island countries]]
* [[List of islands by area]]
* [[List of islands by country]]
* [[List of islands by highest point]]
* [[List of islands by name]]
* [[List of islands by population]]
* [[List of islands by population density]]
* [[List of islands named after people]]
* {{annotated link|Island hopping}}
* {{annotated link|Phantom island}}
* {{annotated link|Private island}}
* {{annotated link|Desert island}}
* {{annotated link|Tidal island}}
* {{annotated link|Rock fever}}
* {{annotated link|Small Island Developing States}}
{{div col end}}

== References ==
{{Reflist}}

== External links ==
* {{commons and category inline|Island|Islands}}
* {{Wikiquote inline|Islands}}

{{Coastal geography|state=collapsed}}

{{Authority control}}

[[Category:Islands| ]]
[[Category:Coastal and oceanic landforms]]
[[Category:Fluvial landforms]]
[[Category:Oceanographical terminology]]
[[Category:Lacustrine landforms]]