Editing Guam (section)

== Geography and environment ==
{{Main|Geography of Guam}}
{{see also|Geology of Guam}}
[[File:Guam ali 2011364 lrg.jpg|thumb|A photograph of Guam from space captured by [[NASA]]'s now decommissioned [[Earth observation satellite]], ''[[Earth Observing-1]]'' (EO-1), December 2011.]]

Guam is {{convert|30.17|mi|km|2|sigfig=4|abbr=off|sp=us}} long and {{convert|4|to|12|mi|km|0|abbr=off|sp=us}} wide. It has an area of {{convert|212|sqmi|km2|0|abbr=off|sp=us}}. It is the [[List of islands of the United States by area|32nd largest island of the United States]]. It is the southernmost and largest island in the [[Mariana Islands]], as well as the largest in [[Micronesia]].<ref>{{Cite web|title=Education Resources: Regional Information, Guam{{!}} PacIOOS|url=https://www.pacioos.hawaii.edu/education/region-guam/|access-date=March 16, 2021|website=Pacific Islands Ocean Observing System (PacIOOS)|language=en-US|archive-date=March 1, 2021|archive-url=https://web.archive.org/web/20210301223100/http://www.pacioos.hawaii.edu/education/region-guam/|url-status=live}}</ref> Guam's [[Point Udall (Guam)|Point Udall]] is the [[List of extreme points of the United States#Interpretation of easternmost and westernmost|westernmost point of the U.S.]], as measured from the [[geographic center of the United States]].<ref>{{cite web |title=The Most Extreme Points of the United States |url=https://www.worldatlas.com/articles/the-most-extreme-points-of-the-united-states.html |website=WorldAtlas |access-date=March 13, 2021 |date=May 28, 2018 |archive-date=February 25, 2021 |archive-url=https://web.archive.org/web/20210225054940/https://www.worldatlas.com/articles/the-most-extreme-points-of-the-united-states.html |url-status=live }}</ref><ref>{{cite web |title=Congressional Record - Proceedings and Debates of the 106th Congress, First Session - House of Representatives (Vol. 145, No. 34) |url=https://www.govinfo.gov/content/pkg/CREC-1999-03-04/pdf/CREC-1999-03-04-house.pdf |archive-url=https://web.archive.org/web/20210508113549/https://www.govinfo.gov/content/pkg/CREC-1999-03-04/pdf/CREC-1999-03-04-house.pdf |archive-date=May 8, 2021 |url-status=live |website=govinfo.gov |access-date=March 13, 2021 |page=H982 |date=March 4, 1999}}</ref>

The Mariana chain, of which Guam is a part, was created by collision of the Pacific and Philippine Sea [[tectonic plate]]s. Guam is located on the micro [[Mariana Plate]] between the two. Guam is the closest land mass to the [[Mariana Trench]], the deep [[subduction|subduction zone]] that runs east of the Marianas. Volcanic eruptions established [[Volcanic island|the base of the island]] in the [[Eocene]], roughly 56 to 33.9 million years ago. The north of Guam is a result of this base being covered with layers of [[coral reef]], turning into [[limestone]], and then being thrust upward by [[Tectonics|tectonic]] activity to create a plateau.<ref name="Guam"/>

The rugged south of the island is a result of more recent volcanic activity. [[Cocos Island (Guam)|Cocos Island]] off the southern tip of Guam is the largest of the many small [[islet]]s along the coastline. Guam's highest point is [[Mount Lamlam]] at {{convert|1334|ft|m|0|abbr=off|sp=us}} above sea level.<ref name="Guam">"Geography of Guam". ''Official site of Guam'', April 19, 2014. Retrieved April 19, 2014, from {{cite web|url=http://ns.gov.gu/geography.html|title=Guam's Geography|access-date=May 2, 2016|url-status=dead|archive-url=https://web.archive.org/web/19961027163532/http://ns.gov.gu/geography.html|archive-date=October 27, 1996}}.</ref> If its base is considered to be the nearby [[Challenger Deep|''Challenger'' Deep]], the deepest surveyed point in the [[Oceans]], Mount Lamlam is the [[List of tallest mountains on Earth|world's tallest mountain]] at {{convert|37820|feet|m}}.<ref>{{cite web |last1=McMahon |first1=Mary |title=How do Scientists Determine the World's Tallest Mountain? |url=https://www.infobloom.com/how-do-scientists-determine-the-worlds-tallest-mountain.htm |website=Info Bloom |access-date=March 13, 2021 |date=January 23, 2021 |archive-date=May 20, 2021 |archive-url=https://web.archive.org/web/20210520184712/https://www.infobloom.com/how-do-scientists-determine-the-worlds-tallest-mountain.htm |url-status=live }}</ref><ref>{{cite web |last1=Fichtl |first1=Marcus |title=Guam's Mount Lamlam technically world's tallest mountain, though most of it is underwater |url=https://www.stripes.com/lifestyle/guam-s-mount-lamlam-technically-world-s-tallest-mountain-though-most-of-it-is-underwater-1.485437 |website=Stars and Stripes |access-date=March 13, 2021 |date=August 31, 2017 |archive-date=November 18, 2020 |archive-url=https://web.archive.org/web/20201118105200/https://www.stripes.com/lifestyle/guam-s-mount-lamlam-technically-world-s-tallest-mountain-though-most-of-it-is-underwater-1.485437 |url-status=live }}</ref>

Politically, Guam is divided into [[villages of Guam|19 villages]]. The majority of the population lives on the coralline limestone plateaus of the north, with political and economic activity concentrated in the central and northern regions. The rugged geography of the south largely limits settlement to rural coastal areas. The western coast is [[Windward and leeward|leeward]] of the [[trade winds]] and is the location of [[Apra Harbor]], the capital [[Hagåtña, Guam|Hagåtña]], and the tourist center of [[Tumon, Guam|Tumon]]. The [[United States Department of Defense|U.S. Defense Department]] owns about 29% of the island,<ref name="VOA_20170809">{{cite news|title=Guam: Small But Important Piece of US Territory in Pacific |url=https://www.voanews.com/a/guam-small-but-important-us-pacific-territory/3979325.html|publisher=Voice of America|language=en |date=August 9, 2017 |archive-date=March 10, 2021 |archive-url=https://web.archive.org/web/20210310070638/https://www.voanews.com/east-asia-pacific/guam-small-important-piece-us-territory-pacific |url-status=live}}</ref> under the management of [[Joint Region Marianas]].
===Climate===
{{further|Climate change in Guam|List of typhoons in Guam}}
[[File:Ritidian Beach - Guam NWR.jpg|thumb|[[Guam National Wildlife Refuge]] beach at [[Ritidian Point]]]]
Guam has a [[tropical rainforest climate]] on the [[Köppen climate classification|Köppen scale]] (Köppen ''Af''). Its driest month of March almost qualifies as a [[tropical monsoon climate]] (Köppen ''Am''). The weather is generally hot and humid throughout the year with little seasonal temperature variation. Guam is known to have equable temperatures year-round. [[Trade winds]] are fairly constant throughout the year. There is often a weak westerly monsoon influence in the summer months.

Guam has two distinct seasons: Wet and dry season. The dry season runs from January through May. June is the transitional period. The wet season runs from July through November. Guam's average annual rainfall was {{convert|98|in|mm|-1|disp=or|sp=us}} between 1981 and 2010.

The wettest month on record at Guam Airport has been August 1997 with {{convert|38.49|in|mm|1}}. The driest was February 2015 with {{convert|0.15|in|mm|1}}. The wettest calendar year was 1976 with {{convert|131.70|in|mm|1}}. The driest year was in 1998 with {{convert|57.88|in|mm|1}}. The most rainfall in a single day occurred on October 15, 1953, when {{convert|15.48|in|mm|1|disp=or|sp=us}} fell.

The mean high temperature is {{convert|86|°F|°C|disp=or}}. The mean low is {{convert|76|°F|°C|1}}. Temperatures rarely exceed {{convert|90|°F|°C|1}} or fall below {{convert|70|°F|°C|1}}. The [[relative humidity]] commonly exceeds 84 percent at night throughout the year, but the average monthly humidity hovers near 66 percent.<ref name="Climatological Report">{{cite web|url=http://www.nws.noaa.gov/climate/getclimate.php?date=&wfo=guam&sid=GUM&pil=CLM&recent=yes&specdate=2013-03-04+15%3A20%3A44|title=Climatological Report|publisher=National Weather Service|access-date=February 26, 2014|date=February 26, 2014|url-status=dead|archive-url=https://web.archive.org/web/20140307004247/http://www.nws.noaa.gov/climate/getclimate.php?date=&wfo=guam&sid=GUM&pil=CLM&recent=yes&specdate=2013-03-04+15%3A20%3A44|archive-date=March 7, 2014}}</ref>

The highest temperature ever recorded in Guam was {{convert|96|F|C|1}} on April 18, 1971, and April 1, 1990.<ref name="Climatological Report"/> A record low of {{convert|69|F|C}} was set on February 1, 2021.<ref>{{cite web |last1=Lloyd |first1=Bruce |title=Guam sets a 71-year record for cold temperature on Saturday |url=https://www.guampdn.com/story/news/2021/01/31/guam-weather-cold-temperature-record-saturday/4334204001/ |website=Pacific Daily News |access-date=March 18, 2021 |date=February 1, 2021}}</ref> The lowest recorded temperature was 65&nbsp;°F (18.3&nbsp;°C), set on February 8, 1973.

Guam lies in the path of [[typhoon]]s<ref>{{cite web|title=National Weather Service Dedicated Forecast Office in Typhoon Alley|url=http://www.publicaffairs.noaa.gov/releases2000/apr00/noaa00r235.html|publisher=US NOAA NWS|access-date=August 19, 2012|date=April 27, 2000|url-status=dead|archive-url=https://web.archive.org/web/20130107012415/http://www.publicaffairs.noaa.gov/releases2000/apr00/noaa00r235.html|archive-date=January 7, 2013}}</ref> and it is common for the island to be threatened by tropical storms and possible typhoons during the wet season. The highest risk of typhoons is from August through November, where typhoons and tropical storms are most probable in the western Pacific. They can, however, occur year-round. Typhoons that have caused major damage on Guam in the American period include the [[1900 Pacific typhoon season#Guam typhoon|Typhoon of 1900]], [[Typhoon Karen|Karen]] (1962), [[Typhoon Pamela (1976)|Pamela]] (1976), [[Typhoon Paka|Paka]] (1997), [[Typhoon Pongsona|Pongsona]] (2002), and [[Typhoon Mawar|Mawar]] (2023).

Since [[Typhoon Pamela (1976)|Typhoon Pamela]] in 1976, wooden structures have been largely replaced by concrete structures.<ref>{{cite web|url=http://www.rms.com/Catastrophe/Models/Guam.asp|work=Risk Management Solutions|title=Guam Catastrophe Model|access-date=June 16, 2007|url-status=dead|archive-url=https://web.archive.org/web/20110207111227/http://www.rms.com/catastrophe/models/Guam.asp|archive-date=February 7, 2011}}</ref><ref>{{cite web|url=http://www.pacificworlds.com/guam/land/winds.cfm|title=Winds|publisher=PacificWorlds.com|access-date=June 16, 2007|url-status=dead|archive-url=https://web.archive.org/web/20070827132157/http://www.pacificworlds.com/guam/land/winds.cfm|archive-date=August 27, 2007}}</ref> During the 1980s, wooden utility poles began to be replaced by typhoon-resistant concrete and steel poles. After the local Government enforced stricter construction codes, many home and business owners have built their structures out of reinforced concrete with installed [[typhoon shutters]].

{{Weather box 
|location = [[Guam International Airport]] (1991–2020 normals, extremes 1945–present)
|single line = Y
|Jan record high F = 94
|Feb record high F = 93
|Mar record high F = 93
|Apr record high F = 96
|May record high F = 94
|Jun record high F = 95
|Jul record high F = 95
|Aug record high F = 94
|Sep record high F = 94
|Oct record high F = 93
|Nov record high F = 92
|Dec record high F = 91
|year record high F = 96

|Jan avg record high F = 88.4
|Feb avg record high F = 88.5
|Mar avg record high F = 89.2
|Apr avg record high F = 90.2
|May avg record high F = 90.8
|Jun avg record high F = 91.1
|Jul avg record high F = 90.8
|Aug avg record high F = 90.6
|Sep avg record high F = 90.4
|Oct avg record high F = 90.4
|Nov avg record high F = 89.9
|Dec avg record high F = 88.8
|year avg record high F = 92.0

|Jan high F = 85.7
|Feb high F = 85.7
|Mar high F = 86.7
|Apr high F = 87.9
|May high F = 88.5
|Jun high F = 88.5
|Jul high F = 87.7
|Aug high F = 87.0
|Sep high F = 87.0
|Oct high F = 87.2
|Nov high F = 87.4
|Dec high F = 86.6
|year high F = 87.2
|Jan mean F = 80.3
|Feb mean F = 80.1
|Mar mean F = 81.0
|Apr mean F = 82.3
|May mean F = 83.0
|Jun mean F = 83.1
|Jul mean F = 82.2
|Aug mean F = 81.5
|Sep mean F = 81.5
|Oct mean F = 81.7
|Nov mean F = 82.2
|Dec mean F = 81.6
|year mean F = 81.7
|Jan low F = 75.0
|Feb low F = 74.6
|Mar low F = 75.4
|Apr low F = 76.7
|May low F = 77.5
|Jun low F = 77.7
|Jul low F = 76.8
|Aug low F = 76.1
|Sep low F = 76.0
|Oct low F = 76.3
|Nov low F = 77.0
|Dec low F = 76.5
|year low F = 76.3

|Jan avg record low F = 71.6
|Feb avg record low F = 71.4
|Mar avg record low F = 71.9
|Apr avg record low F = 73.3
|May avg record low F = 74.1
|Jun avg record low F = 74.6
|Jul avg record low F = 73.8
|Aug avg record low F = 73.4
|Sep avg record low F = 73.3
|Oct avg record low F = 73.4
|Nov avg record low F = 73.9
|Dec avg record low F = 73.3
|year avg record low F = 70.2

|Jan record low F = 66
|Feb record low F = 65
|Mar record low F = 66
|Apr record low F = 68
|May record low F = 70
|Jun record low F = 70
|Jul record low F = 70
|Aug record low F = 70
|Sep record low F = 70
|Oct record low F = 67
|Nov record low F = 68
|Dec record low F = 68
|year record low F = 65
|precipitation colour = green
|Jan precipitation inch = 5.34
|Feb precipitation inch = 4.15
|Mar precipitation inch = 2.77
|Apr precipitation inch = 3.50
|May precipitation inch = 4.45
|Jun precipitation inch = 6.51
|Jul precipitation inch = 12.25
|Aug precipitation inch = 17.66
|Sep precipitation inch = 15.17
|Oct precipitation inch = 12.73
|Nov precipitation inch = 8.29
|Dec precipitation inch = 5.30
|year precipitation inch = 98.12
|unit precipitation days = 0.01 in
|Jan precipitation days = 20.1
|Feb precipitation days = 18.0
|Mar precipitation days = 18.3
|Apr precipitation days = 18.9
|May precipitation days = 19.7
|Jun precipitation days = 23.2
|Jul precipitation days = 26.0
|Aug precipitation days = 25.9
|Sep precipitation days = 25.1
|Oct precipitation days = 25.4
|Nov precipitation days = 23.9
|Dec precipitation days = 22.7
|year precipitation days = 267.2
|Jan humidity = 83.7
|Feb humidity = 81.9
|Mar humidity = 83.1
|Apr humidity = 82.0
|May humidity = 82.7
|Jun humidity = 82.7
|Jul humidity = 87.3
|Aug humidity = 88.7
|Sep humidity = 88.8
|Oct humidity = 88.3
|Nov humidity = 86.6
|Dec humidity = 83.0
|year humidity = 84.9
|Jan sun = 176.0
|Feb sun = 173.7
|Mar sun = 216.4
|Apr sun = 214.0
|May sun = 219.9
|Jun sun = 193.8
|Jul sun = 156.1
|Aug sun = 142.2
|Sep sun = 132.7
|Oct sun = 132.6
|Nov sun = 135.0
|Dec sun = 143.4
|year sun = 2035.8
|Jan percentsun = 50
|Feb percentsun = 53
|Mar percentsun = 58
|Apr percentsun = 57
|May percentsun = 56
|Jun percentsun = 50
|Jul percentsun = 39
|Aug percentsun = 37
|Sep percentsun = 36
|Oct percentsun = 36
|Nov percentsun = 39
|Dec percentsun = 41
|year percentsun = 46
|source 1 = [[NOAA]] (relative humidity and sun 1961–1990)<ref name= NOAA>{{cite web
| url = https://www.weather.gov/wrh/Climate?wfo=gum
| title = NowData - NOAA Online Weather Data
| publisher = National Oceanic and Atmospheric Administration
| access-date = September 11, 2021
| archive-date = September 6, 2021
| archive-url = https://web.archive.org/web/20210906150411/https://www.weather.gov/wrh/Climate?wfo=gum
| url-status = live
}}</ref><ref name=NCEI>{{cite web
| url = https://www.ncei.noaa.gov/access/services/data/v1?dataset=normals-monthly-1991-2020&startDate=0001-01-01&endDate=9996-12-31&stations=GQW00041415&format=pdf
| title = Station: Guam INTL AP, GU GQ
| work = U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991-2020)
| publisher = National Oceanic and Atmospheric Administration
| access-date = September 11, 2021
| archive-date = September 11, 2021
| archive-url = https://web.archive.org/web/20210911151301/https://www.ncei.noaa.gov/access/services/data/v1?dataset=normals-monthly-1991-2020&startDate=0001-01-01&endDate=9996-12-31&stations=GQW00041415&format=pdf
| url-status = live
}}</ref><ref name=NOAAsun>
{{cite web
| archive-url = https://web.archive.org/web/20210911151125/https://www.ncei.noaa.gov/pub/data/normals/WMO/1961-1990/TABLES/REG__V/U1/91217.TXT
| archive-date = September 11, 2021
| url = https://www.ncei.noaa.gov/pub/data/normals/WMO/1961-1990/TABLES/REG__V/U1/91217.TXT
| title = WMO Climate Normals for Guam/Marshall Islands, PI 1961–1990
| publisher = National Oceanic and Atmospheric Administration
| access-date = September 11, 2021}}</ref> 
}}

=== Ecology ===
{{main|Marianas tropical dry forests}}
{{further|List of endemic plants in the Mariana Islands|List of threatened, endangered and extinct species in the Mariana Islands|Invasive species in Guam|Climate change in Guam|Guam National Wildlife Refuge}}
[[File:Ficus prolixa interwoven canopy. 1000 Steps hiking trail, Pagat, Guam.jpg|thumb|Hiking in Guam's limestone forest.]]
Guam is home to a diverse array of ecosystems,<ref>{{Cite web |title=Natural Environment - Guampedia |url=https://www.guampedia.com/category/natural-environment/ |access-date=2025-01-02 |website=www.guampedia.com}}</ref><ref>{{Cite web |last=Murphy |first=Shannon |date=2011-02-13 |title=Ancient Guam's Environment - Guampedia |url=https://www.guampedia.com/ancient-guams-environment/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref> including coral reefs,<ref>{{Cite web |last=Pereda |first=Nathalie |date=2019-10-10 |title=Coral Reefs: Essential Ecosystems on Guam - Guampedia |url=https://www.guampedia.com/coral-reefs-essential-ecosystems-on-guam/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref> deep seas, sea grasses,<ref>{{Cite web |last=Murphy |first=Shannon |date=2009-10-01 |title=Seagrasses Overview - Guampedia |url=https://www.guampedia.com/seagrasses-overview/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref> beach strand, mangroves,<ref>{{Cite web |last=Pereda |first=Nathalie |date=2017-08-04 |title=Mangroves: The Forest Between Land and Sea - Guampedia |url=https://www.guampedia.com/mangroves-the-forest-between-land-and-sea/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref> a variety of different [[Marianas tropical dry forests|limestone forest]] types,<ref>{{Cite web |last=Pereda |first=Nathalie |date=2019-10-02 |title=Limestone Forests of Guam - Guampedia |url=https://www.guampedia.com/limestone-forests-of-guam/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref><ref>{{Cite journal |last=Fosberg |first=F. Raymond |date=1960 |title=The Vegetation of Micronesia. 1, General descriptions, the vegetation of the Marianas Islands, and a detailed consideration of the vegetation of Guam |url=https://digitallibrary.amnh.org/items/b7a6abd7-e958-47d7-98aa-89efd6c2da30 |journal=Bulletin of the AMNH |volume=119 |issue=1 |via=American Museum of Natural History}}</ref> volcanic forests and grasslands,<ref>{{Cite web |last=Pereda |first=Nathalie |date=2017-08-04 |title=Badlands in Southern Guam - Guampedia |url=https://www.guampedia.com/badlands-in-southern-guam/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref> [[List of rivers of Guam|riparian systems]], and caves.<ref>{{Cite web |last=Pereda |first=Nathalie |date=2019-10-02 |title=Guam's Amazing Caves - Guampedia |url=https://www.guampedia.com/guams-amazing-caves/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref> There are approximately 17 species of plant that are endemic only to the island of Guam, and many more that are [[List of endemic plants in the Mariana Islands|endemic to the Mariana Islands]].  Numerous endemic insects have been described.<ref>{{Cite book |url=http://hbs.bishopmuseum.org/pubs-online/pdf/bull172.pdf |title=Insects of Guam-I, Bulletin 172 |date=1942 |publisher=Bernice P. Bishop Museum}}</ref><ref>{{Cite book |url=http://hbs.bishopmuseum.org/pubs-online/pdf/bull189.pdf |title=Insects of Guam-II, Bulletin 189 |date=1946 |publisher=Bernice P. Bishop Museum}}</ref><ref>{{Cite web |title=Insects of Micronesia |url=http://hbs.bishopmuseum.org/pubs-online/iom.html |access-date=2025-01-02 |website=hbs.bishopmuseum.org}}</ref>  There are approximately 29 [[List of land snails of the Mariana Islands|land snails]] listed as endemic to the island of Guam, although many are now endangered or presumed extinct.<ref>{{Cite web |last=Murphy |first=Shannon |date=2013-04-23 |title=Land Snails (Akaleha') of the Mariana Islands - Guampedia |url=https://www.guampedia.com/land-snails-akaleha-of-the-mariana-islands/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref><ref>{{Cite book |last1=Kerr |first1=Alexander M. |url=https://www.uog.edu/_resources/files/ml/technical_reports/148Kerr_and_Bauman_2013_UOGMLTechReport148.pdf |title=Annotated Checklist of the Land snails of the Mariana Islands, Micronesia |last2=Bauman |first2=Scott |date=2013 |publisher=University of Guam (UOG)}}</ref>  Guam once hosted 14 kinds of terrestrial [[List of birds of Guam|birds]], 7 of which were endemic to Guam on the species or subspecies level, although all but one of the 14 are now [[List of threatened, endangered and extinct species in the Mariana Islands|extinct, extirpated, or endangered]].<ref>{{Cite web |last=Murphy |first=Shannon |date=2009-09-30 |title=Native Forest Birds of Guam - Guampedia |url=https://www.guampedia.com/a-native-forest-birds-of-guam/ |access-date=2025-01-02 |website=www.guampedia.com |language=en-US}}</ref> Three locations on Guam ([[Guam National Wildlife Refuge]], [[Cocos Island (Guam)|Cocos Island]], and Mahlac Caves) have been identified as [[Important Bird Area|Important Bird Areas]] (IBA) by [[BirdLife International]] because they support populations of [[Micronesian starling|Micronesian starlings]], [[Mariana swiftlet|Mariana swiftlets]], [[Mariana crow|Mariana crows]], and Guam rails. The [[Guam rail]] became the second bird species to ever be downlisted from [[Extinct in the wild]] after a population was established on Cocos Island.<ref>{{Cite web |date=2019-12-10 |title=Species recoveries bring hope amidst the biodiversity crisis - IUCN Red List {{!}} IUCN |url=https://iucn.org/news/species/201912/species-recoveries-bring-hope-amidst-biodiversity-crisis-iucn-red-list |access-date=2025-01-07 |website=iucn.org |language=en}}</ref> Guam was home to three native bat species: the [[Guam flying fox|little Mariana fruit bat]] (''Pteropus tokudae''), now extinct; the endangered [[Pacific sheath-tailed bat]] (''Emballonura semicaudata rotensis''); and the endangered [[Mariana fruit bat]] (''Pteropus mariannus mariannus'').

[[File:20140402-APHIS-UNK-0004 (13592983734).jpg|thumb|The introduction of the [[brown tree snake]] nearly eradicated the native bird population.]]
Guam has experienced severe effects of [[invasive species]] upon the natural [[biodiversity]] of the island. These include the [[local extinction]] of endemic bird species after the introduction of the [[brown tree snake]], an infestation of the [[Oryctes rhinoceros|coconut rhinoceros beetle]] destroying [[coconut]] palms, and the effect of introduced [[feral]] [[mammal]]s and [[amphibian]]s.

[[Wildfire]]s plague the forested areas of Guam every [[dry season]] despite the island's humid climate. Most fires are caused by humans with 80% resulting from [[arson]].<ref>{{cite web|url=http://www.guamforestry.org/docs/final_guam_2004.pdf|title=Territory of Guam Fire Assessment January 2004|access-date=March 24, 2009|url-status=dead|archive-url=https://web.archive.org/web/20090324224423/http://www.guamforestry.org/docs/final_guam_2004.pdf|archive-date=March 24, 2009}}, pp. 6–7, guamforestry.org</ref> Poachers often start fires to attract deer to the new growth. Invasive grass species that rely on fire as part of their natural life cycle grow in many regularly burned areas. Grasslands and "barrens" have replaced previously forested areas leading to greater soil erosion.<ref name="National Park Service">{{cite web|url=http://www.nps.gov/archive/wapa/indepth/Park/Natural/fire/fireguam.htm|archive-url=https://web.archive.org/web/20071213232039/http://www.nps.gov/archive/wapa/indepth/Park/Natural/fire/fireguam.htm|archive-date=December 13, 2007|work=[[United States Department of the Interior]]|author=National Park Service|title=Fire and Guam|access-date=June 16, 2007|author-link=National Park Service}}</ref>

During the rainy season, sediment is carried by the heavy rains into the [[Fena Lake]] Reservoir and [[Ugum River]], leading to water quality problems for southern Guam. Eroded silt also destroys the marine life in reefs around the island. Soil stabilization efforts by volunteers and forestry workers (planting trees) have had little success in preserving natural habitats.<ref name="National Park Service" />[[File:Fish and coral in Tumon Bay Marine Preserve, Guam.jpg|thumb|Previously extensively [[dredging|dredged]], [[Tumon Bay]] is now a marine preserve.]]
Efforts have been made to protect Guam's coral reef habitats from pollution, eroded silt and overfishing, problems that have led to decreased fish populations. This has both ecological and economic value, as Guam is a significant [[Underwater diving on Guam|vacation spot for scuba divers]], and one study found that Guam's reefs are worth [[US$]]127 million per year.<ref>{{cite news |last1=Brown |first1=Val |title=Guam's Reefs are Important to Guam's Culture and Economy |url=https://www.newspapers.com/image/646794275 |access-date=October 1, 2021 |work=Pacific Daily News |date=May 30, 2008 |location=Agana Heights, Guam |page=5 |quote=The results indicated that Guam's reefs are worth $127 million per year |archive-date=October 1, 2021 |archive-url=https://web.archive.org/web/20211001213252/http://www.newspapers.com/image/646794275/ |url-status=live }}</ref> In recent years, the Department of Agriculture, Division of Aquatic and Wildlife Resources has established several new marine preserves where fish populations are monitored by biologists.<ref>{{cite news |url=http://www.guampdn.com/guampublishing/special-sections/mlsea/8-future.htm |archive-url=https://archive.today/20130103031256/http://www.guampdn.com/guampublishing/special-sections/mlsea/8-future.htm |url-status=dead |archive-date=January 3, 2013 |work=Pacific Daily News |title=Guam's Marine Preserves |last=Brown |first=Valerie |date=2006}}</ref> These are located at [[Pati Point]], [[Piti Bomb Holes]], [[Sasa Bay]], Achang Reef Flat, and [[Tumon Bay]].<ref>{{cite web |title=Sea Life |url=https://www.visitguam.com/chamorro-culture/nature/sea-life/ |website=Guam Visitors Bureau |access-date=May 20, 2020 |archive-date=May 31, 2020 |archive-url=https://web.archive.org/web/20200531225300/https://www.visitguam.com/chamorro-culture/nature/sea-life/ |url-status=live }}</ref>

Before adopting [[United States Environmental Protection Agency|U.S. Environmental Protection Agency]] standards, portions of Tumon Bay were dredged by the hotel chains to provide a better experience for hotel guests.<ref>{{cite web|url=http://www.guamepa.govguam.net/programs/epr/sediment_report.pdf|work=EPA Guam Report|title=Management of Contaminated Harbor Sediments in Guam|url-status=live|archive-url=https://web.archive.org/web/20070808031615/http://www.guamepa.govguam.net/programs/epr/sediment_report.pdf|archive-date=August 8, 2007}}</ref><ref>{{cite web|url=http://www.pcrguam.com/press_releases/Tumon_Bay.htm|work=Directions Magazine; June/July 1996|title=Tumon Bay – Engineering a Better Environment|author=Packbier, Paul E.R.|access-date=October 19, 2011|url-status=dead|archive-url=https://web.archive.org/web/20110726141402/http://www.pcrguam.com/press_releases/Tumon_Bay.htm|archive-date=July 26, 2011}}</ref> Tumon Bay has since been made into a preserve. A federal [[Guam National Wildlife Refuge]] in northern Guam protects the decimated [[sea turtle]] population in addition to a small colony of [[Mariana fruit bats]].<ref>{{cite journal|last=Holmes III|first=Rolston|title=Environmental Ethics in Micronesia, Past and Present, Part II—Guam Today: Still "on the Edge." Colonial Legacy and American Presence|journal=International Society for Environmental Ethics Newsletter|volume=12|issue=3|year=2001|url=http://www.cep.unt.edu/ISEE/n12-3-01.htm|access-date=June 16, 2007|archive-url=https://web.archive.org/web/20070609092403/http://www.cep.unt.edu/ISEE/n12-3-01.htm|archive-date=June 9, 2007|url-status=live}}</ref>

Harvest of sea turtle eggs was a common occurrence on Guam before World War II. The [[green sea turtle]] (''Chelonia mydas'') was harvested legally on Guam before August 1978, when it was listed as threatened under the Endangered Species Act. The [[hawksbill sea turtle]] (''Eretmochelys imbricata'') has been on the endangered list since 1970. In an effort to ensure the protection of sea turtles on Guam, routine sightings are counted during aerial surveys and nest sites are recorded and monitored for hatchlings.