Editing Diego Garcia (section)

==Natural history==
No species of plant, bird, amphibian, reptile, mollusc, crustacean or mammal is [[Endemism|endemic]] on Diego Garcia or the surrounding waters, though some species of fish and aquatic invertebrates are endemic. All plants, wildlife, and aquatic species are protected to some degree.

Much of the lagoon and other waters of Diego Garcia are protected wetlands, following an application by the UK in 2004 to obtain [[Ramsar site]] wetlands conservation status,<ref>{{cite web |url=http://www.ukotcf.org/pdf/Ramsar/61BIOT.pdf |archive-url=https://web.archive.org/web/20061005133603/http://www.ukotcf.org/pdf/Ramsar/61BIOT.pdf |archive-date=5 October 2006 |url-status=live |title=Information Sheet on Ramsar Wetlands: Chagos Banks |publisher=United Kingdom Overseas Territories Conservation Forum |date=13 November 2004 |access-date=27 September 2011}}</ref> and large parts of the island are nature preserves.<ref>[[#Sheppard Spalding|Sheppard & Spalding (2003)]], chapter 6.</ref>

===Geography===
[[File:Biot-travel-svg-map.svg|thumb|A location map of Diego Garcia]]
Diego Garcia is the largest land mass in the Chagos Archipelago (which includes [[Peros Banhos]], the [[Salomon Islands]], the [[Three Brothers (islands), Chagos|Three Brothers]], the [[Egmont Islands]], and the [[Great Chagos Bank]]), being an atoll occupying approximately {{convert|174|km2|sqmi|sigfig=2}}, of which {{convert|27.19|km2|sqmi|sigfig=2}} is dry land.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], paragraph 2.4.1.</ref> The continuous portion of the atoll rim stretches {{convert|64|km|sigfig=2|abbr=on}} from one end to the other, enclosing a lagoon {{convert|21|km|0|abbr=on}} long and up to {{convert|11|km|0|abbr=on}} wide, with a {{convert|6|km|0|adj=on|abbr=on}} pass opening at the north. Three small islands are located in the pass.<ref name="ReferenceA"/>

The island consists of the largest continuous dryland rim of all atolls in the world. The dryland rim varies in width from a few hundred metres to 2.4&nbsp;km. Typical of coral atolls, it has a maximum elevation on some dunes on the ocean side of the rim of {{convert|9|m|ft|abbr=off}} above mean low water. The rim nearly encloses a lagoon about {{convert|19|km|mi|abbr=on}} long and up to {{convert|8|km|mi|abbr=on}} wide. The atoll forms a nearly complete rim of land around a lagoon, enclosing 90% of its [[perimeter]], with an opening only in the north. The main island is the largest of about 60 islands which form the Chagos Archipelago. Besides the main island, three small islets are at the mouth of the lagoon: West Island ({{convert|3.4|ha|acre|abbr=on}}), Middle Island ({{convert|6|ha|acre|abbr=on}}) and East Island ({{convert|11.75|ha|acre|abbr=on}}). A fourth, Anniversary Island, 1&nbsp;km (1,100 [[yards]]) southwest of Middle Island, appears as just a sand bar on satellite images. Both Middle Island and Anniversary Island are part of the Spur Reef complex.<ref name="ReferenceA">[[#NRMP|Natural Resources Management Plan (2005)]], paragraph 2.5.1.</ref>

The total area of the atoll is about {{convert|170|km2|sqmi|sigfig=2|abbr=on}}. The lagoon area is roughly {{convert|120|km2|sqmi|sigfig=2|abbr=on}} with depths ranging down to about {{convert|25|m|ft|abbr=on}}. The total land area (excluding peripheral reefs) is around {{convert|30|km2|sqmi|sigfig=2|abbr=on}}. The coral reef surrounding the seaward side of the atoll is generally broad, flat, and shallow around {{convert|1|m|ft|abbr=on}} below mean sea level in most locations and varying from {{convert|100|to|200|m|ft|abbr=on}} in width. This fringing seaward reef shelf comprises an area around {{convert|35.2|km2|sqmi|sigfig=2|abbr=on}}. At the outer edge of the reef shelf, the bottom slopes very steeply into deep water, at some locations dropping to more than {{convert|450|m|ft|sigfig=2|abbr=on}} within {{convert|1|km|mi|abbr=on}} of the shore.<ref name="ReferenceA"/>

In the lagoon, numerous coral heads present hazards to navigation. The shallow reef shelf surrounding the island on the ocean side offers no ocean-side anchorage. The channel and anchorage areas in the northern half of the lagoon are [[dredge]]d, along with the pre-1971 ship [[turning basin]]. Significant saltwater wetlands called [[barachois]] exist in the southern half of the lagoon. These small lagoons off of the main lagoon are filled with [[seawater]] at high tide and dry at low tide. Scientific expeditions in 1996 and 2006 described the lagoon and surrounding waters of Diego Garcia, along with the rest of the Chagos Archipelago, as "exceptionally unpolluted" and "pristine".<ref>{{cite web|url=http://www.chagos-trust.org/science.asp |title=Science of the Chagos – Chagos Conservation Trust |access-date=16 June 2009 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20090616185943/http://www.chagos-trust.org/science.asp |archive-date=16 June 2009 }}</ref>

Diego Garcia is frequently subject to earthquakes caused by [[Plate tectonics|tectonic plate]] movement along the [[Carlsberg Ridge]] located just to the west of the island. One was recorded in 1812; one measuring 7.6 on the Richter Scale hit on 30 November 1983, at 23:46 local time and lasted 72 seconds, resulting in minor damage including wave damage to a 50-m stretch of the southern end of the island, and another on 2 December 2002, an earthquake measuring 4.6 on the Richter scale struck the island at 12:21&nbsp;am.<ref name="realhistory" />{{Better source needed|date=July 2023}}

In December 2004, [[2004 Indian Ocean earthquake and tsunami|a tsunami generated near Indonesia]] caused minor shoreline erosion on Barton Point (the northeast point of the atoll of Diego Garcia).<ref>[http://www.reefnewmedia.co.uk/cmt_chagos/uploads/PDF/Newsletters/ChagosNews25.pdf Chagos News, No. 25, p. 2] {{webarchive |url=https://web.archive.org/web/20120119025950/http://www.reefnewmedia.co.uk/cmt_chagos/uploads/PDF/Newsletters/ChagosNews25.pdf |date=19 January 2012 }}</ref>

===Oceanography===
Diego Garcia lies within the influence of the [[South Equatorial Current]] year-round. The surface currents of the Indian Ocean also have a monsoonal regimen associated with the Asian Monsoonal wind regimen.{{Citation needed|date=November 2023}} Sea surface temperatures are in the range of {{convert|80|–|84|F|C}} year-round.<ref name="NAVCENT2002">[[#NAVCENT|Local Area Forecaster's Handbook (2002)]], p. 13.</ref>

===Fresh water supply===
Diego Garcia is the above-water rim of a coral atoll composed of [[Holocene]] coral rubble and sand to the depth of about {{convert|36|m|ft|abbr=on}}, overlaying [[Pleistocene]] limestone deposited at the then-sea level on top of a [[seamount]] rising about {{convert|1800|m|ft|abbr=on}} from the floor of the Indian Ocean. The Holocene sediments are porous and completely saturated with sea water. Any rain falling on the above-water rim quickly percolates through the surface sand and encounters the salt water underneath. Diego Garcia is of sufficient width to minimise tidal fluctuations in the [[aquifer]], and the rainfall (in excess of 102.5&nbsp;inches/260&nbsp;cm per year on average)<ref>[[#NRMP|Natural Resources Management Plan (2005)]], paragraph 2.5.2.</ref> is sufficient in amount and periodicity for the fresh water to form a series of convex, freshwater, [[Ghyben-Herzberg lenses]] floating on the heavier salt water in the saturated sediments.<ref name="bare_url">{{cite web |url=http://geography.about.com/library/misc/ucghyben.htm |title=Salt Water vs. Fresh Water – Ghyben-Herzberg Lens |publisher=Geography.about.com |date=9 April 2012 |access-date=21 June 2012 |archive-date=5 December 2010 |archive-url=https://web.archive.org/web/20101205001839/http://geography.about.com/library/misc/ucghyben.htm |url-status=dead }}</ref><ref name="Urish">[[#Urish|Urish (1974)]], p. 27.</ref>

The horizontal structure of each lens is influenced by variations in the type and porosity of the subsurface deposits, which on Diego Garcia are minor. At depth, the lens is globular; near the surface, it generally conforms to the shape of the island.<ref>[[#Urish|Urish (1974)]], p. 28.</ref> When a Ghyben-Herzberg lens is fully formed, its floating nature will push a [[Hydraulic head|freshwater head]] above [[mean sea level]], and if the island is wide enough, the depth of the lens below mean sea level will be 40 times the height of the water table above sea level. On Diego Garcia, this equates to a maximum depth of 20 m. However, the actual size and depth of each lens is dependent on the width and shape of the island at that point, the permeability of the aquifer, and the equilibrium between recharging rainfall and losses to evaporation to the atmosphere, transpiration by plants, tidal advection, and human use.

In the plantation period, shallow wells, supplemented by rainwater collected in [[cistern]]s, provided sufficient water for the pastoral lifestyle of the small population. On Diego Garcia today, the military base uses over 100 shallow "horizontal" wells to produce over 560,000 L per day from the "Cantonment" lens on the northwest arm of the island—sufficient water for western-style usage for a population of 3,500. This 3.7&nbsp;km<sup>2</sup> lens holds an estimated 19 million m<sup>3</sup> of fresh water and has an average daily recharge from rainfall over 10,000 m<sup>3</sup>, of which 40% remains in the lens and 60% is lost through [[evapotranspiration]].<ref>Hunt, Charles D. "Hydrogeology of Diego Garcia". In: [[#Vacher|Vacher & Quinn (1997)]], pp. 909–929. {{doi|10.1016/S0070-4571(04)80054-2}}.</ref>

Extracting fresh water from a lens for human consumption requires careful calculation of the sustainable yield of the lens by season because each lens is susceptible to corruption by [[saltwater intrusion]] caused by overuse or drought. In addition, overwash by tsunamis and tropical storms has corrupted lenses in the Maldives and several Pacific islands. Vertical wells can cause salt upcoming into the lens, and overextraction will reduce freshwater pressure resulting in lateral intrusion by seawater. Because the porosity of the surface soil results in virtually zero runoff, lenses are easily polluted by fecal waste, burials, and chemical spills. Corruption of a lens can take years to "flush out" and reform, depending on the ratio of recharge to losses.<ref name="bare_url" />

A few natural depressions on the atoll rim capture the abundant rainfall to form areas of freshwater wetlands.<ref name="Stoddart_127_142">D. R. Stoddart (1971): "Land vegetation of Diego Garcia". In: [[#Stoddart|Stoddart & Taylor (1971)]], pp. 127–142.</ref> Two are of significance to island wildlife and to recharge their respective freshwater lenses. One of these is centred on the northwest point of the atoll; another is found near the Point Marianne Cemetery on the southeast end of the airfield. Other, smaller freshwater wetlands are found along the east side of the runway, and in the vicinity of the receiver antenna field on the northwest arm of the atoll.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], paragraph 3.3.2.1.</ref>

Also, several man-made freshwater ponds resulted from excavations made during construction of the airfield and road on the western half of the atoll rim. These fill from rainfall and from extending into the Ghyben-Herzberg lenses found on this island.<ref>Stephen W. Surface and Edward F.C. Lau, "Fresh Water Supply System Developed on Diego Garcia", The Naval Civil Engineer, Winter 1985</ref>

===Climate===
[[File:Island couple.jpg|thumb|Eclipse Point]]
Diego Garcia has an equatorial [[tropical rainforest climate]] ([[Köppen climate classification|Köppen]] ''Af''). The surrounding sea surface temperature is the primary climatic control, and temperatures are generally uniform throughout the year, with an average maximum of {{convert|30|C|F}} by day during March and April, and {{convert|29|C|F}} from July to September. Diurnal variation is roughly {{convert|3|-|4|C-change|F-change}}, falling to the low {{convert|27|°C|°F|abbr=on}} by night.<ref name="NAVCENT_2002"/> Humidity is high throughout the year. The almost constant breeze keeps conditions reasonably comfortable.

From December through March, winds are generally westerly around {{convert|6|kn|km/h}}. During April and May, winds are light and variable, ultimately backing to an east-southeasterly direction. From June through September, the influence of the Southeast trades is felt, with speeds of 10–15 knots. During October and November, winds again go through a period of light and variable conditions veering to a westerly direction with the onset of summer in the Southern Hemisphere.<ref name="NAVCENT_2002"/>

All [[precipitation (meteorology)|precipitation]] falls as [[rainfall|rain]], characterised by air mass-type showers. Annual rainfall averages {{convert|2603.5|mm|in|abbr=on}}, with the heaviest precipitation from September to April. January is the wettest month with {{convert|353|mm|in|abbr=on}} of mean monthly precipitation, and August the driest month, averaging {{convert|106.5|mm|in|abbr=on}} of mean monthly precipitation.<ref name="NAVCENT_2002"/>

[[Thunderstorm]] activity is generally noticed in the afternoon and evening during the summer months (December through March), when the [[Intertropical Convergence Zone]] is in the vicinity of the island.<ref name="NAVCENT_2002">[[#NAVCENT|Local Area Forecaster's Handbook (2002)]], p. 14.</ref>

Diego Garcia is at minimum risk from [[tropical cyclone]]s due to its proximity to the [[equator]] where the [[Coriolis effect|coriolis parameter]] required to organise circulation of the [[upper atmosphere]] is minimal. Low-intensity storms have hit the island, including one in 1901, which blew over 1,500 coconut trees;<ref>[[#Edis|Edis (2004)]], p. 71.</ref> one on 16 September 1944,<ref>{{cite web |first=Ted |last=Morris |url=http://www.zianet.com/tedmorris/dg/pby.html |title=Diego Garcia – The PBY Catalina |publisher=Zianet.com |date=19 September 2002 |access-date=21 June 2012 |archive-date=12 May 2011 |archive-url=https://web.archive.org/web/20110512172819/http://www.zianet.com/tedmorris/dg/pby.html |url-status=live }}</ref>{{Better source needed|date=July 2023}} which caused the wreck of a Royal Air Force PBY Catalina; one in September 1990 which demolished the tent city then being constructed for United States Air Force bomber crews during Operation Desert Storm;<ref name="realhistory">{{cite web |url=http://www.zianet.com/tedmorris/dg/realhistory.html |title=Important Dates of the Provisional People's Democratic Republic of Diego Garcia |access-date=27 September 2011 |date=29 August 2011 |archive-date=11 June 2011 |archive-url=https://web.archive.org/web/20110611005507/http://www.zianet.com/tedmorris/dg/realhistory.html |url-status=live }}</ref>{{Better source needed|date=July 2023}} and one on 22 July 2007, when winds exceeded {{convert|60|kn|km/h|abbr=on}} and over {{convert|250|mm|in|abbr=on}} of rain fell in 24 hours.<ref name="realhistory"/>{{Better source needed|date=July 2023}}

[[File:Degar sunset from cannon point.jpg|thumb|left|Sunset at Cannon Point]]
The island was somewhat affected by the [[tsunami]] caused by the [[2004 Indian Ocean earthquake]]. Service personnel on the western arm of the island reported only a minor increase in wave activity. The island was protected to a large degree by its favourable [[ocean topography]]. About {{convert|80|km|mi|abbr=on}} east of the atoll lies the {{convert|650|km|mi|adj=mid|-long}} Chagos Trench, an underwater canyon plunging more than {{convert|4900|m|ft|abbr=on}}. The depth of the trench and its grade to the atoll's slope and shelf shore makes it more difficult for substantial tsunami waves to build before passing the atoll from the east. In addition, near-shore [[coral reef]]s and an algal platform may have dissipated much of the waves' impact.<ref>[http://www.estripes.com/article.asp?section=104&article=26265 "Diego Garcia Navy base reports no damage from quake, tsunamis"] {{webarchive|url=https://web.archive.org/web/20110927024535/http://www.estripes.com/article.asp?section=104&article=26265 |date=27 September 2011 }}. Leo Shane&nbsp;III, ''Stars and Stripes''. 28 December 2004. URL accessed 1 June 2006.</ref><ref name=chagosnews>{{Cite journal|last=Sheppard |first=Charles |title=The Tsunami, Shore Erosion and Corals in the Chagos Islands |journal=Chagos News |volume=25 |pages=2–7 |issn=1355-6746 |date=April 2005 |url=http://www.chagosconservationtrust.org/pages/Chagos%20News/ChagosNews25.pdf |access-date=21 February 2008 |url-status=dead |archive-url=https://web.archive.org/web/20081003104800/http://www.chagosconservationtrust.org/pages/Chagos%20News/ChagosNews25.pdf |archive-date=3 October 2008 }}</ref> A biological survey conducted in early 2005 indicated erosional effects of the tsunami wave on Diego Garcia and other islands of the Chagos Archipelago. One {{convert|200|to|300|m|yd|adj=on|abbr=on}} stretch of shoreline was found to have been breached by the tsunami wave, representing about 10% of the eastern arm. A biological survey by the Chagos Conservation Trust reported that the resulting inundation additionally washed away shoreline shrubs and small to medium-sized coconut palms.<ref name=chagosnews/>

{{Weather box
|location = Diego Garcia (extremes 1951–2021)
|metric first = yes
|single line = yes
|collapsed = Y
|width = auto
|temperature colour = pastel
|Jan record high C = 36.1
|Feb record high C = 37.2
|Mar record high C = 36.1
|Apr record high C = 35.0
|May record high C = 36.1
|Jun record high C = 35.0
|Jul record high C = 33.0
|Aug record high C = 32.4
|Sep record high C = 34.2
|Oct record high C = 34.9
|Nov record high C = 35.1
|Dec record high C = 37.2
|year record high C = 37.2
|Jan high C = 29.8
|Feb high C = 30.3
|Mar high C = 30.9
|Apr high C = 30.9
|May high C = 30.2
|Jun high C = 29.4
|Jul high C = 28.7
|Aug high C = 28.7
|Sep high C = 29.0
|Oct high C = 29.4
|Nov high C = 29.8
|Dec high C = 30.1
|year high C = 29.7
|Jan mean C = 27.1
|Feb mean C = 27.4
|Mar mean C = 27.6
|Apr mean C = 27.8
|May mean C = 27.5
|Jun mean C = 26.8
|Jul mean C = 26.3
|Aug mean C = 26.1
|Sep mean C = 26.4
|Oct mean C = 26.7
|Nov mean C = 27.0
|Dec mean C = 27.2
|year mean C = 27.0
|Jan low C = 24.7
|Feb low C = 25.0
|Mar low C = 25.4
|Apr low C = 25.7
|May low C = 25.4
|Jun low C = 24.7
|Jul low C = 24.2
|Aug low C = 24.1
|Sep low C = 24.2
|Oct low C = 24.3
|Nov low C = 24.7
|Dec low C = 24.8
|year low C = 24.8
|Jan record low C = 20.0
|Feb record low C = 20.0
|Mar record low C = 17.8
|Apr record low C = 21.1
|May record low C = 17.8
|Jun record low C = 17.8
|Jul record low C = 17.2
|Aug record low C = 20.0
|Sep record low C = 21.1
|Oct record low C = 16.1
|Nov record low C = 21.7
|Dec record low C = 18.3
|year record low C = 16.1
|rain colour = green
|Jan rain mm = 340
|Feb rain mm = 279
|Mar rain mm = 213
|Apr rain mm = 194
|May rain mm = 167
|Jun rain mm = 147
|Jul rain mm = 144
|Aug rain mm = 145
|Sep rain mm = 244
|Oct rain mm = 281
|Nov rain mm = 221
|Dec rain mm = 273
|year rain mm = 2648
|unit rain days = 0.3 mm
|Jan rain days = 22
|Feb rain days = 19
|Mar rain days = 18
|Apr rain days = 17
|May rain days = 15
|Jun rain days = 15
|Jul rain days = 17
|Aug rain days = 16
|Sep rain days = 16
|Oct rain days = 20
|Nov rain days = 19
|Dec rain days = 20
|year rain days = 212
|Jan humidity = 80
|Feb humidity = 79
|Mar humidity = 78
|Apr humidity = 77
|May humidity = 79
|Jun humidity = 79
|Jul humidity = 79
|Aug humidity = 79
|Sep humidity = 80
|Oct humidity = 79
|Nov humidity = 79
|Dec humidity = 78
|year humidity = 79
|source 1 = [[Deutscher Wetterdienst]]<ref name = DWD>{{cite web
| url = http://www.dwd.de/DWD/klima/beratung/ak/ak_619670_kt.pdf
| title = Klimatafel von Diego Garcia, Chagos-Archipel / Indischer Ozean / Großbritannien
| work = Baseline climate means (1961–1990) from stations all over the world
| publisher = Deutscher Wetterdienst
| language = de
| access-date = 18 October 2016
| archive-date = 2 April 2019
| archive-url = https://web.archive.org/web/20190402152842/https://www.dwd.de/DWD/klima/beratung/ak/ak_619670_kt.pdf
| url-status = live
}}</ref>
|source 2 =  Meteo Climat (record highs and lows)<ref name = meteoclimat>{{cite web
| url = http://meteo-climat-bzh.dyndns.org/index.php?page=stati&id=1983
| title = Station Diego Garcia
| publisher = Meteo Climat
| language = fr
| access-date = 26 August 2021
| archive-date = 24 February 2021
| archive-url = https://web.archive.org/web/20210224213049/http://meteo-climat-bzh.dyndns.org/index.php?page=stati&id=1983
| url-status = live
}}</ref>
}}

===Vegetation===
[[File:Diego Garcia Mixed Species Marsh.png|thumb|A mixed-species freshwater wetland on Diego Garcia]]

The first [[botanical]] observations of the island were made by Hume in 1883, when the coconut plantations had been in operation for a full century. Subsequent studies and collections during the plantation era were made in 1885, 1905, 1939, and 1967.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], Appendix E1, p. 1.</ref> Thus, very little of the nature of the precontact vegetation is known.

The 1967 survey, published by the [[Smithsonian]]<ref>[[#Stoddart|Stoddart & Taylor (1971)]]{{page needed|date=September 2011}}</ref> is used as the most authoritative baseline for more recent research. These studies indicate the vegetation of the island may be changing rapidly. For example, J. M. W. Topp collected data annually between 1993 and 2003 and found that on the average three new plant species arrived each year, mainly on Diego Garcia. His research added fully a third more species to Stoddart.<ref>[[#Topp|Topp (1988)]], p. 2.</ref> Topp and Martin Hamilton of [[Kew Gardens]] compiled the most recent checklist of vegetation in 2009.<ref>[[#Hamilton|Hamilton & Topp (2009)]]</ref>

[[File:Diego Garcia Cocos Forest.png|thumb|left|upright|A thick forest of coconuts on Diego Garcia]]
In 1967, Stoddart described the land area of Diego Garcia as having a [[littoral zone|littoral]] [[hedge]] of ''[[Scaevola taccada]]'', while inland, ''[[Coconut|Cocos nucifera]]'' (coconut) was the most dominant tree, covering most of the island. The substory was either managed and park-like, with understory less than 0.5 m in height, or consisted of what he called "Cocos Bon-Dieu"&nbsp;– an intermediate story of juvenile trees and a luxuriant ground layer of self-sown seedlings&nbsp;– causing those areas to be relatively impenetrable.<ref name="Stoddart_143_160">F. R. Fosberg & A. A. Bullock (1971): "List of Diego Garcia vascular plants". In: [[#Stoddart|Stoddart & Taylor (1971)]], pp. 143–160.</ref>

Also, areas of remnant tropical hardwood forest are at the sites of the plantation-era villages, as well as ''[[Casuarina equisetifolia]]'' (iron wood pines) woodlands.<ref name="Stoddart_127_142"/>

In 1997, the United States Navy contracted a vegetation survey that identified about 280 species of terrestrial [[vascular plant]]s on Diego Garcia.<ref>[[#Sheppard Seaward|Sheppard & Seaward (1999)]], p. 225.</ref> None of these was [[Endemism|endemic]], and another survey in 2005 identified just 36 species as "native", meaning arriving without the assistance of humans, and found elsewhere in the world.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], Appendix E2, paragraph E2-2.</ref> No [[terrestrial plant]] species are of any conservation-related concern at present.<ref>[[#Sheppard Spalding|Sheppard & Spalding (2003)]], p. 40.</ref>
[[File:Diego Garcia Hernandia Forest.png|thumb|A ''Hernandia''-dominated forest on Diego Garcia]]

Of the 36 native vascular plants on Diego Garcia, 12 are trees, five are [[shrub]]s, seven are [[dicotyledon]] herbs, three are grasses, four are [[vine]]s, and five are [[fern]]s.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], Appendix E1, p. 4-3.</ref>

The 12 tree species are: ''[[Barringtonia asiatica]]'' (fish-poison tree), ''[[Calophyllum inophyllum]]'' (Alexandrian laurel), ''[[Cocos nucifera]]'', ''[[Cordia subcordata]]'', ''[[Guettarda speciosa]]'', ''[[Intsia bijuga]]'', ''[[Hernandiaceae|Hernandia sonora]]'', ''[[Morinda citrifolia]]'', ''[[Neisosperma oppositifolium]]'',<ref>{{cite web|url=http://www.ars-grin.gov/~sbmljw/cgi-bin/taxon.pl?412139 |archive-url=https://web.archive.org/web/20150903221255/http://www.ars-grin.gov/~sbmljw/cgi-bin/taxon.pl?412139 |url-status=dead |archive-date=3 September 2015 |title=''Neisosperma oppositifolium'' (Lam.) Fosberg & Sachet |publisher=[[United States Department of Agriculture]] |work=[[Germplasm Resources Information Network]] |access-date=27 September 2011 }}</ref> ''[[Pisonia grandis]]'', ''[[Terminalia catappa]]'', and ''[[Heliotropium foertherianum]]''. Another three tree species are common, and may be native, but they may also have been introduced by humans: ''Casuarina equisetifolia'', ''[[Hibiscus tiliaceus]]'', and ''[[Pipturus|Pipturus argenteus]]''.

The five native shrubs are: ''[[Caesalpinia bonduc]]'', ''[[Pemphis|Pemphis acidula]]'', ''[[Premna|Premna serratifolia]]'', ''Scaevola taccada'' (often mispronounced "Scaveola"), and ''[[Suriana|Suriana maritima]]''.

[[File:Premna Shrubland.png|thumb|right|A ''Premna''-dominated scrub land on Diego Garcia]]
Also, 134 species of plants are classified as "weedy" or "naturalised alien species", being those unintentionally introduced by man, or intentionally introduced as ornamentals or crop plants which have now "gone native", including 32 new species recorded since 1995, indicating a very rapid rate of introduction.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], Appendix E1, p. 4-5.</ref> The remainder of the species list consists of cultivated food or ornamental species, grown in restricted environments such as a planter's pot.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], Appendix E1, p. 4-6.</ref>

[[File:Diego Garcia Cattail Marsh.png|thumb|upright|A freshwater marsh composed entirely of cattails located on the eastern edge of the bomber ramp on Diego Garcia]]

[[File:Diego Garcia Littoral Scrub 1.png|thumb|A typical oceanside littoral hedge with ''Casuarina'' fringe]]

In 2004, 10 [[plant community|plant communities]] were recognised on the atoll rim:<ref name="ReferenceA"/>
* ''Calophyllum'' forest, dominated by ''Calophyllum inophyllum'', with trunks that can grow in excess of {{convert|2|m|ft}} in diameter. This forest often contains other species such as ''Hernandia sonora'', ''Cocos nucifera'', and ''Guettarda speciosa'' with a ''Premna obtusifolia'' edge. When found on the beaches, ''Calophyllum'' often extends over the lagoon water and supports nesting red-footed boobies, as does ''Barringtonia asiatica'' found mostly on the eastern arm of the atoll.
* ''Cocos'' forest, essentially monotypic (''Cocos bon Dieu''), with the understory consisting of coconut seedlings
* ''Cocos-Hernandia'' forest, dominated by two canopy species—''C. nucifera'' and ''H. sonora''
* ''Cocos-Guettarda'' forest, dominated by the canopy species ''C. nucifera'' and ''G. speciosa'': The understory consists of a mix of ''Neisosperma oppositifolium'', with ''Scaevola taccada'' and ''Tournefortia argentea'' on the beach edge.
* ''Hernandia'' forest, dominated at the canopy level by ''H. sonora'': The most representative areas of this forest type are on the eastern, undeveloped part of the atoll. ''Calophyllum inophyllum'' and ''C. nucifera'' are often present. Understory species in this forest are often ''Morinda citrifolia'', ''Cocos'' seedlings, and ''[[Asplenium nidus]]'' (bird's nest fern), and occasionally, ''N. oppositifolium'' and ''G. speciosa''.
* ''Premna'' shrubland, occurring generally between marshy areas and forested areas: The most conspicuous vegetation is primarily ''P. obtusifolia'', with ''Casuarina equisetifolia'' and ''Scaevola taccada'' on the margins. The dense groundcover consists of species such as ''[[Fimbristylis|Fimbristylis cymosa]]'', ''[[Ipomoea pes-caprae]]'' (beach morning glory) and ''[[Triumfetta|Triumfetta procumbens]]''. ''Premna'' shrubland appears mostly adjacent to the developed areas of the atoll, particularly in the well fields.
* Littoral scrub lines almost the entire seashore and lagoon shore of the island. It is dominated by ''S. taccada'', but it also contains scattered coconut trees, ''G. speciosa'' and ''Pisonia grandis''. On the seaward side, it also contains ''Tournefortia argentea'' and ''Suriana maritima''. On the lagoon side, it may also contain ''[[Lepturus|Lepturus repens]]'', ''[[Triumfetta|Triumfetta procumbens]]'' and ''[[Cyperus|Cyperus ligularis]]''. Large pockets of ''Barringtonia asiatica'' are also on the eastern edge of the lagoon.
* Maintained areas of grasses and sedges routinely mowed: Aerial photographs of the island clearly display large areas of grasslands and park-like [[savanna]] upon which the United States military has constructed large outdoor facilities such as antenna fields and the airport.<ref>{{cite web |author=President for Life |url=http://www.zianet.com/tedmorris/dg/aerial2.html |title=Aerial Photographs of Diego Garcia |publisher=Zianet.com |access-date=21 June 2012 |archive-date=11 June 2011 |archive-url=https://web.archive.org/web/20110611010333/http://www.zianet.com/tedmorris/dg/aerial2.html |url-status=live }}</ref>{{Better source needed|date=July 2023}}
* Mixed native forest, with no dominant canopy species
* Marshes are divided into three different types: cattail (''[[Typha domingensis]]''), wetland, and mixed species. Cattail marshes contained almost entirely cattails. These areas are often man-made reservoirs or drainages that have been almost entirely monotypic. Wetlands were based upon vegetation that occurred in the area with fresh water. Mixed-species marshes were highly variable and usually had no standing water.

===Wildlife===
[[File:Coconut Crab.jpg|thumb|[[Coconut crab]]s are protected on Diego Garcia.]]
All the terrestrial and aquatic fauna of Diego Garcia are protected, with the exception of certain game fish, rats, and cats; hefty fines are levied against violators.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], Appendix B.</ref>

====Crustaceans====
The island is a haven for several types of [[crustacean]]; "warrior crabs" (''[[Cardisoma carnifex]]'') overrun the jungle at night. The extremely large {{convert|4|kg|lb|adj=on}} [[coconut crab]] or robber crab (''Birgus latro'') is found here in large numbers. Because of the protections provided the species on this atoll, and the isolation of the east rim of the atoll, the species is recorded in greater densities there than anywhere else in its range (339 crabs/ha).<ref>[[#NRMP|Natural Resources Management Plan (2005)]], Appendix G, p. G-7.</ref>

====Mammals====
No [[mammal]] species are native on Diego Garcia, with no record of bats.<ref name="Stoddart_163_170">Stoddarrt, D. R. (1971): "Terrestrial fauna of Diego Garcia and other Chagos atolls". In: [[#Stoddart|Stoddart & Taylor (1971)]], pp. 163–170.</ref> Other than rats (''[[Rattus rattus]]''), all "wild" mammal species are feral descendants of domesticated species. During the plantation era, Diego Garcia was home to large herds of Sicilian donkeys (''[[Equus asinus]]''), dozens of horses (''[[Equus caballus]]''), hundreds of dogs (''[[Canis familiaris]]''), and house cats (''[[Felis catus]]''). In 1971, the BIOT Commissioner ordered the extermination of [[Free-ranging dog#Feral dogs|feral dogs]] following the departure of the last plantation workers, and the program continued through 1975, when the last feral dog was observed and shot.<ref>Bruner, Phillip, "Avifaunal and Feral Mammal Survey of Diego Garcia, Chagos Archipelago, British Indian Ocean Territory", 17 October 1995, pp. 3–23.</ref> Donkeys, which numbered over 400 in 1972, were down to just 20 individuals in 2005.<ref name="NRMP_G_4_27">[[#NRMP|Natural Resources Management Plan (2005)]], Appendix G, p. 4.27.</ref> The last horse was observed in 1995,<ref name="NRMP_G_4_27"/> and by 2005, just two cats were thought to have survived an island-wide eradication program.{{Citation needed|date=August 2010}}

====Native birds====
[[File:Red-tailed Tropicbird3.jpg|thumb|left|Several pairs of [[red-tailed tropicbird]] nest near the cantonment area.]]

The total bird list for the Chagos Archipelago, including Diego Garcia, consists of 91 species, with large breeding populations of 16 species. Although no birds are endemic, internationally important seabird colonies exist. Diego Garcia's seabird community includes thriving populations of species which are rapidly declining in other parts of the Indian Ocean. Large nesting colonies of [[brown noddy|brown noddies]], [[bridled tern]]s, the [[lesser noddy]], [[red-footed booby]] and [[lesser frigatebird]]s exist on Diego Garcia.

Other nesting native birds include [[red-tailed tropicbird]]s, [[wedge-tailed shearwater]]s, [[tropical shearwater]], [[black-naped tern]]s, [[white tern]]s, [[striated heron]]s, and [[white-breasted waterhen]]s.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], paragraph 4.2.2.1.1.</ref> The 680-hectare [[Barton Point Nature Reserve]] was identified as an [[Important Bird Area]] for its large breeding colony of red-footed boobies.<ref>{{cite web|url=http://www.birdlife.org |title=Barton Point Nature Reserve |access-date=21 October 2012 |work=Important Bird Areas factsheet |publisher=BirdLife International |year=2012 |url-status=dead |archive-url=https://web.archive.org/web/20070710124603/http://www.birdlife.org/ |archive-date=10 July 2007 }}</ref>

====Introduced birds====
The island hosts introduced bird species from many regions, including cattle egrets (''[[Bubulcus ibis]]''), Indian barred ground dove, also called the zebra dove (''[[Geopelia striata]]''), turtle dove (''[[Nesoenas picturata]]''), Indian mynah (''[[Acridotheres tristis]]''), Madagascar fody (''[[Foudia madagascariensis]]''), and chickens (''[[Gallus gallus]]'').<ref>[[#NRMP|Natural Resources Management Plan (2005)]], paragraph 4.2.2.1.3.</ref>
{{Clear left}}

====Terrestrial reptiles and freshwater amphibians====
Currently, three lizards and one toad are known to inhabit Diego Garcia, and possibly one snake. All are believed to have been introduced by human activity. The house gecko (''[[Hemidactylus frenatus]]''), the mourning gecko (''[[Lepidodactylus lugubris]]''), the garden lizard (an agamid) (''[[Calotes versicolor]]''), and the cane toad (''[[Bufo marinus]]'').<ref>[[#NRMP|Natural Resources Management Plan (2005)]], paragraph 4.2.2.6.</ref> A viable population of a type of blind snake from the family Typhlopidae may be present, probably the brahminy blind snake (''[[Ramphotyphlops braminus]]''). This snake feeds on the larvae, eggs, and pupae of [[ant]]s and [[termite]]s, and is about the size of a large earthworm.

====Sea turtles====
Diego Garcia provides suitable foraging and nesting habitat for both the hawksbill turtle (''[[Eretmochelys imbricata]]'') and the green turtle (''[[Chelonia mydas]]''). Juvenile hawksbills are quite common in the lagoon and at Barachois Sylvane (also known as Turtle Cove) in the southern part of the lagoon. Adult hawksbills and greens are common in the surrounding seas and nest regularly on the ocean-side beaches of the atoll. Hawksbills have been observed nesting during June and July, and from November to March. Greens have been observed nesting in every month; the average female lays three clutches per season, each having an average clutch size of 113 eggs. [[Diurnality|Diurnal]] nesting is common in both species. An estimated 300–700 hawksbills and 400–800 greens nest in the Chagos.<ref>[[#NRMP|Natural Resources Management Plan (2005)]], Appendix K, pp. K-2–K-3.</ref>

====Endangered species====
Four reptiles and six cetaceans are endangered and may or may not be found on or around Diego Garcia:<ref>[[#NRMP|Natural Resources Management Plan (2005)]], paragraph 4.4.</ref>
Hawksbill turtle (''[[hawksbill turtle|Eretmocheyls imbricata]]'') – known; leatherback turtle (''[[Dermochelys coriacea]]'') – possible; green turtle (''Chelonia mydas'') – known; olive ridley turtle (''[[olive ridley|Lepidochelys oliveacea]]'') – possible; sperm whale (''[[Physeter macrocephalus]]'') – possible; sei whale (''[[Sei whale|Balaeonoptera borealis]]'') – possible;
finback whale (''[[Fin whale|Balaeonoptera physalus]]'') – possible; Bryde's whale (''[[Bryde's whale|Balaeonoptera edeni]]'') – possible; blue whale (''[[blue whale|Balaeonoptera musculus]]'') – possible; humpback whale (''[[Megaptera novaeangliae]]'') – possible; southern right whale (''[[Eubalaena australis]]'') – possible.<ref>Carroll L.E.. 2011. [https://researchspace.auckland.ac.nz/bitstream/handle/2292/11541/whole.pdf?sequence=9 Return of the Right Whale: Assessment of Abundance, Population Structure and Geneflow in the New Zealand Southern Right Whale] {{Webarchive|url=https://web.archive.org/web/20160304134152/https://researchspace.auckland.ac.nz/bitstream/handle/2292/11541/whole.pdf?sequence=9 |date=4 March 2016 }}. [[University of Auckland]]. Retrieved on 25 November 2015</ref>