Marianas Tropical Dry Forests
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The Marianas tropical dry forests is a
tropical and subtropical dry broadleaf forests The tropical and subtropical dry broadleaf forest is a habitat (ecology), habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-roun ...
ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...
on the
Marianas Islands The Mariana Islands ( ; ), also simply the Marianas, are a crescent-shaped archipelago comprising the summits of fifteen longitudinally oriented, mostly dormant volcanic mountains in the northwestern Pacific Ocean, between the 12th and 21st pa ...
in the western
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
.


Geography

The Marianas Islands extend 900 km north and south. The islands were formed by the subduction of the Pacific Plate under the
Mariana Plate The Mariana plate is a micro tectonic plate located west of the Mariana Trench which forms the basement of the Mariana Islands which form part of the Izu–Bonin–Mariana Arc. It is separated from the Philippine Sea plate to the west by a dive ...
, and the
Marianas Trench The Mariana Trench is an oceanic trench located in the western Pacific Ocean, about east of the Mariana Islands; it is the deepest oceanic trench on Earth. It is crescent-shaped and measures about in length and in width. The maximum known ...
, the world's deepest, lies immediately east of the islands. The nine northern islands are volcanic and relatively young; Farallon de Pájaros, the northernmost, is an active
stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...
. Several of the northern islands have experienced recent volcanic activity. Anatahan erupted in 2003, Pagan in 1981, and Asuncion and Guguan in 1906.Williams, Laura & Radley, Paul & Castro, Tony & Vogt, Scott. (2009). Wildlife and Vegetation surveys of Asuncion Island, Technical Report #15, 2009. 10.13140/RG.2.1.1175.7600. The southern islands are older, and are composed of volcanic rocks and marine limestone uplifted by the colliding plates.
Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...
, the southernmost island, is the largest. Other southern islands include
Saipan Saipan () is the largest island and capital of the Northern Mariana Islands, an unincorporated Territories of the United States, territory of the United States in the western Pacific Ocean. According to 2020 estimates by the United States Cens ...
,
Tinian Tinian () is one of the three principal islands of the Commonwealth of the Northern Mariana Islands (CNMI). Together with uninhabited neighboring Aguiguan, it forms Tinian Municipality, one of the four constituent municipalities of the Northern ...
, and Rota. Politically the islands are divided between the territory of
Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...
and the
Commonwealth of the Northern Mariana Islands The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI), is an unincorporated territory and commonwealth of the United States consisting of 14 islands in the northwestern Pacific Ocean.Lin, Tom C.W.Amer ...
, both part of the United States.


Climate

The climate of the Mariana Islands is tropical. Temperature varies little from season to season, and average monthly temperatures range from 24º to 27º C. Rainfall averages 2,000 and 2,500 mm annually and is strongly seasonal, with a wet season from July through October. Easterly trade winds are fairly constant, with an occasional weak westerly monsoon influence during the summer months.


Flora

Plant communities on the northern islands include grassland on young volcanic soils. Older and lower-elevation lava flows are colonized by the tree ''
Casuarina equisetifolia ''Casuarina equisetifolia'', commonly known as coastal she-oak, horsetail she-oak, ironwood, beach sheoak, beach casuarina, whistling tree or Australian pine is a species of flowering plant in the family Casuarinaceae and is native to Australia, ...
'', known locally as ''gagu'', and the fern '' Nephrolepsis hirsutula''. Small patches of ''
Pisonia grandis ''Pisonia grandis'', the grand devil's-claws, is a species of flowering tree in the ''Bougainvillea'' family, Nyctaginaceae. Description The tree has broad, thin leaves, smooth bark and bears clusters of green sweet-smelling flowers that matur ...
'' forest can be found on the four younger islands which are free of grazing goats. The four larger northern islands, Agrihan, Pagan, Sarigan, and Anatahan, are home to remnant ''Aglaia–Elaeocarpus'' forests. The characteristic trees are mapunyao (''
Aglaia mariannensis ''Aglaia mariannensis'' ( Chamorro: mapunyao or mapuñao; Carolinian: ), is a tree endemic to the Mariana Islands, including Guam and the Northern Mariana Islands, with large (about 10–18 cm in length) dark green, glossy pinnately compoun ...
'') and yonga ('' Elaeocarpus joga''). Mapunyao is endemic to the Marianas, and yonga is endemic to Micronesia. Mapunyao is dominant in the forest understory on both limestone and volcanic soils. Yonga is a large tree with a spreading crown, although the Marianas' frequent typhoons often limits their growth to 15 meters. Yonga's fleshy bright-blue berries are an important food for forest birds, particularly fruit doves. Asuncion has a ''
Terminalia Terminalia may refer to: * Terminalia (festival) Terminalia () was an ancient Roman festival in honour of the god Terminus, who presided over boundaries. His statue was merely a stone or post stuck in the ground to distinguish between propert ...
'' forest, unique in the archipelago, whose principal species are endemic. Most of the natural vegetation on the older southern islands has been cleared or altered by humans, but areas of primary and secondary forest remain. The plant communities vary with elevation and soils. Areas with volcanic substrates have highly weathered lateritic clays (oxisols or ultisols) or very young inceptisols. The limestone terrain has thin to moderately thick soils, with areas of bare stone. In the remnant primary limestone forests of Saipan ''
Pisonia grandis ''Pisonia grandis'', the grand devil's-claws, is a species of flowering tree in the ''Bougainvillea'' family, Nyctaginaceae. Description The tree has broad, thin leaves, smooth bark and bears clusters of green sweet-smelling flowers that matur ...
'' is the dominant tree. ''
Dendrocnide latifolia ''Dendrocnide'' is a genus of approximately 40 species of plants in the nettle family ''Urticaceae''. They have a wide distribution across North East India, Southeast Asia, Australia and the Pacific Islands. In Australia they are commonly known a ...
,
Cynometra ramiflora A tree in the family Fabaceae, ''Cynometra ramiflora'' is found in mangroves and flooded forests from New Caledonia in the western Pacific west to Queensland in Australia, New Guinea, Maritime Southeast Asia, Island Southeast Asia, and Tropical A ...
,
Intsia bijuga ''Intsia bijuga'', commonly known as Borneo teak, ipil, merbau, Johnstone River teak, and kwila, amongst many other names, is a species of tree in the flowering plant family Fabaceae, native to coastal areas from east Africa, through India and ...
'', and ''
Erythrina variegata ''Erythrina variegata'', commonly known as tiger's claw or Indian coral tree, is a species of ''Erythrina'' native to the tropical and subtropical regions of eastern Africa, the Indian subcontinent, northern Australia, and the islands of the Ind ...
'' are very common, and ''
Premna serratifolia ''Premna serratifolia'' is a species of small tree or shrub in the family Lamiaceae. It blooms and fruits between May and November.Described by Dr. N Sasidharan (Dr. B P Pal Fellow), Kerala Forest Research Institute, Peechi in India biodiversity ...
,
Ficus prolixa ''Ficus'' ( or ) is a genus of about 850 species of woody trees, shrubs, vines, epiphytes and hemiepiphytes in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending int ...
'', and ''
Ficus tinctoria ''Ficus tinctoria'', also known as dye fig, or humped fig is a hemiepiphytic tree of genus ''Ficus''. It is also one of the species known as '' strangler fig''. It is found in Asia, Malesia, northern Australia, and the South Pacific islands. It ...
''. ''
Meiogyne cylindrocarpa ''Meiogyne cylindrocarpa'', commonly known as fingersop or native apricot in Australia, is a small tree or shrub in the custard apple family Annonaceae, native to parts of tropical Asia and Australasia. Description ''Meiogyne cylindrocarpa'' i ...
'' is a shrub or small tree common in the understory and infrequent in the canopy. Most of Guam is covered by secondary forest. Patches of primary forest survive on the northern plateau and in inaccessible areas. The limestone forests are of five types. In ''Artocarpus-Ficus'' forests, the tall wild breadfruit ''
Artocarpus mariannensis ''Artocarpus mariannensis'' ( Chamorro: ''dugdug''), also known as the Marianas breadfruit or the seeded breadfruit, is a species of plant in the mulberry / fig family, Moraceae. It is endemic to the Mariana Islands and Guam. It has been utilize ...
'' and the banyan ''Ficus prolixa'' are co-dominant. Lower-stature ''Mammea'' forests, dominated by ''
Mammea odorata ''Mammea'' is a flowering plant genus with about 70 species in the family Calophyllaceae.Stephens, P.F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008. http://www.mobot.org/MOBOT/Research/APweb/ Its members are evergreen trees ...
'', are found on the eastern escarpment. ''Cordia'' forests, dominated by ''
Cordia subcordata ''Cordia subcordata'' is a species of flowering tree in the borage family. It can be found growing in eastern Africa, South Asia, Southeast Asia, northern Australia and the Pacific Islands including Hawaii. The plant is known by a variety of na ...
'', are found on steep slopes and cliffs. ''Merrilliodendron-Ficus'' forest is dominated by '' Merrilliodendron megacarpum'' and ''Ficus prolixa'' which form a canopy 30 to 45 meters high. ''Pandanus'' forest is dominated by ''
Pandanus tectorius ''Pandanus tectorius'' is a species of ''Pandanus'' (screwpine) that is native to Malesia, Papuasia, eastern Australia, and the Pacific Islands. It grows in the coastal lowlands typically near the edge of the ocean. Common names in English inclu ...
''. Vegetation on volcanic soils is predominantly grassland with forests growing in ravines. Ravine forest trees include ''Pandanus tectorius, P. dubuis,
Hibiscus tiliaceus ''Hibiscus tiliaceus'', commonly known as the sea hibiscus or coast cottonwood, is a species of flowering tree in the mallow family, Malvaceae, with a pantropical distribution along coastlines. It has also been introduced to Florida and New Zeal ...
, Ficus prolixa, Glochidion marianum'', and ''Premna serratifolia''. Dense thickets of ''
Leucaena leucocephala ''Leucaena leucocephala'' is a small fast-growing Mimosoideae, mimosoid tree native to southern Mexico and northern Central America (Belize and Guatemala) and is now naturalized throughout the tropics including parts of Asia. Common names inclu ...
'', a South American tree widely planted after World War II, are common. Endemic plants include the endangered ''
Serianthes nelsonii ''Serianthes nelsonii'' is a large tree endemic to Guam and Rota of the Mariana Islands. Only one mature tree existed on Guam (until November 2024, when it was announced it perished to the consequences of deforestation by the U.S. Military an ...
'' on Guam and Rota, ''
Aglaia mariannensis ''Aglaia mariannensis'' ( Chamorro: mapunyao or mapuñao; Carolinian: ), is a tree endemic to the Mariana Islands, including Guam and the Northern Mariana Islands, with large (about 10–18 cm in length) dark green, glossy pinnately compoun ...
'', and ''
Heritiera longipetiolata ''Heritiera longipetiolata'' ( Chamorro: Ufa-hålomtåno) is a species of flowering plant in the family Malvaceae. It is found in Guam, Northern Mariana Islands, and possibly Micronesia. It is threatened by habitat loss. See also List of endem ...
'', which grows only in crevices on the limestone outcrops and cliffs of Saipan, Tinian, Rota, and Guam.


Fauna

There are eight endemic species of birds in the Marianas – the Mariana fruit dove (''Ptilinopus roseicapilla''),
Mariana swiftlet The Mariana swiftlet or Guam swiftlet (''Aerodramus bartschi'') is a species of swiftlet in the family Apodidae. Taxonomy It was formerly lumped with the island swiftlet (''Aerodramus inquietus''). Description The swiftlet is about in length ...
(''Aerodramus bartschi''),
Guam rail The Guam rail (''Hypotaenidia owstoni''), known locally and in Chamorro as ''ko'ko, is a small, terrestrial bird endemic to Guam in the Rallidae family. They are one of the island's few remaining endemic bird species. The species became extinc ...
(''Hypotaenidia owstoni''), Tinian monarch (''Metabolus takatsukasae''),
Mariana crow The Mariana crow (''Corvus kubaryi'') ( Chamorro name: ''åga'') is a species of the crow family from the tropical Western Pacific. It is a glossy black bird about long and known only from the islands of Guam and Rota. It is a rare bird which ...
(''Corvus kubaryi''),
golden white-eye The golden white-eye (''Cleptornis marchei'') is a species of bird in the white-eye family, Zosteropidae. It is the only species within the genus ''Cleptornis''. The golden white-eye was once considered to be a honeyeater in the family Meliphag ...
(''Cleptornis marchei''),
Rota white-eye The Rota white-eye or Rota bridled white-eye (''Zosterops rotensis'') is a species of bird in the family Zosteropidae. It is critically endangered and endemic to Rota in the Northern Mariana Islands, where it mainly occurs in mature, wet limesto ...
(''Zosterops rotensis''), and
Saipan white-eye The bridled white-eye (''Zosterops conspicillatus'') (Chamorro language, Chamorro name: ''nosa'') is a species of white-eye native to the Mariana Islands and formerly Guam. The species' natural habitat is tropical forests, shrublands and urban ar ...
(''Zosterops saypani''). The
Guam flycatcher The Guam flycatcher (''Myiagra freycineti''), or Guam broadbill, is an extinct species of bird in the family Monarchidae formerly endemic to Guam. Taxonomy and systematics Some authorities consider the Guam flycatcher to have been a subspecies o ...
(''Myiagra freycineti'') is extinct.BirdLife International (2020) Endemic Bird Areas factsheet: Mariana Islands. Downloaded from http://www.birdlife.org on 29/11/2020. Limited-range species include the
White-throated ground dove The white-throated ground dove (''Pampusana xanthonura'') is a species of ground dove in the genus ''Pampusana''. It is classified as near-threatened. This species was formerly in the genus ''Alopecoenas'' Sharpe, 1899, but the name of the gen ...
(''Alopecoenas xanthonurus'') of the Marianas and Yap; the
Micronesian myzomela The Micronesian myzomela (''Myzomela rubratra'') is a species of bird in the honeyeater family Meliphagidae. The species forms a superspecies with a number of related and similar looking island and mainland myzomelas across the Pacific and Austra ...
(''Myzomela rubratra'') of the Marianas, Caroline Islands, and Palau; the
Caroline swiftlet The Caroline swiftlet (''Aerodramus inquietus''), also known as the island swiftlet, Micronesian swiftlet, or Caroline Islands swiftlet, is a species of Swift (bird), swift in the family Apodidae. Some Taxonomy (biology), taxonomists consider it ...
(''Aerodramus inquietus'') of the Marianas and Carolines; and the
Micronesian starling The Micronesian starling (''Aplonis opaca'') is a species of starling in the family Sturnidae. It is found in Micronesia, from the Northern Mariana Islands to Palau and all the way into eastern Micronesia. Its natural habitats are subtropical or ...
(''Aplonis opaca'') of the Marianas, Carolines, and Palau. The endangered
Marianas megapode The Micronesian megapode or Micronesian scrubfowl (''Megapodius laperouse'') is an endangered megapode which inhabits islands of the Western Pacific Ocean. Description The Micronesian megapode is a stocky medium-sized bird that is mostly dark b ...
(''Megapodius laperouse laperouse'') and the skink ''
Emoia slevini ''Emoia slevini'', also known commonly as the Mariana skink, Slevin's brown skink, Slevin's emo skink, and Slevin's skink, is a species of lizard in the family Scincidae. The species is endemic to the Mariana Islands. Etymology The specific na ...
'' are now found only in the ''Terminalia'' forests of Asuncion. However, there have been recent megapode sightings on Saipan and its adjacent islet of Managaha. Guam's native bird and lizard species have been decimated by the
Australasian Australasia is a subregion of Oceania, comprising Australia, New Zealand (overlapping with Polynesia), and sometimes including New Guinea and surrounding islands (overlapping with Melanesia). The term is used in a number of different contexts, ...
brown tree snake The brown tree snake (''Boiga irregularis''), also known as the brown catsnake, is an arboreal rear-fanged colubrid snake native to eastern and northern coastal Australia, eastern Indonesia (Sulawesi to Papua), Papua New Guinea, and many island ...
(''Boiga irregularis''), which was introduced in the 1940s. The two extant native mammal species are bats. The Marianas flying fox (''Pteropus mariannus'') lives on inaccessible vegetated limestone cliffs and volcanic ravine forests. The only
Pacific sheath-tailed bat The Pacific sheath-tailed bat or Polynesian sheath-tailed bat (''Emballonura semicaudata'') is a species of sac-winged bat in the family Emballonuridae found in American Samoa, Fiji, Guam, Micronesia, Palau, Samoa (where it is called ''pe'a vai, ...
s (''Emballonura semicaudata'') in the Marianas are found on
Aguijan Aguijan (; ; also Aguiguan and Aguihan, based on the Spanish rendition of the native name) is a small bean-shaped uninhabited coralline island in the Northern Mariana Islands chain in the Pacific Ocean. It is situated south-west of Tinian, from ...
. The
Guam flying fox The Guam flying fox (''Pteropus tokudae''), also known as the little Marianas fruit bat, is an extinct species of small megabat endemic to Guam in the Marianas Islands in Micronesia that was confirmed extinct due to hunting or habitat changes. It ...
(''Pteropus tokudae'') was last seen in the 1960s and is presumed extinct. The islands are home to several endemic land snails, including '' Succinea piratarum'' and ''
Succinea quadrasi ''Succinea quadrasi'' is a species of air-breathing land snail, a terrestrial gastropod mollusc in the family Succineidae, the amber snails. Distribution This species is endemic to Guam Guam ( ; ) is an island that is an Territories of ...
''.


Protected areas

Protected areas include:UNEP-WCMC (2020). Protected Area Profile for Guam from the World Database of Protected Areas, November 2020. Available at: www.protectedplanet.net *
Guam National Wildlife Refuge The Guam National Wildlife Refuge is composed of three units: the Andersen Air Force Base Overlay Unit (Air Force Overlay Unit), the Navy Overlay Unit, and the Ritidian Unit. The Ritidian Unit ( CHamoru: ''Puntan Litekyan'') is on the northernmo ...
(4.93 km2), established in 1993, protects a portion of Guam's northern coast. * Bolanos Conservation Area (12 km2) on southern Guam * Asuncion Island Preserve (7.29 km2) on Asuncion Island * Guguan Island Preserve (4.24 km2) on Guguan * Sabana Protected Area (15.21 km2) on Rota * I Chenchon Park Wildlife Conservation Area and Bird Sanctuary (3.29 km2) on Rota * Wedding Cake Mountain Wildlife Conservation Area (1.21 km2) on Rota * Kagman Conservation Area (1.63 km2) on Saipan


References


External links

* {{WWF ecoregion, name=Marianas tropical dry forests, id=oc0203
Marianas tropical dry forests (DOPA)

Marianas tropical moist forests (Encyclopedia of Earth)
Mariana Islands Ecoregions of the United States Oceanian ecoregions Tropical and subtropical dry broadleaf forests Endemic Bird Areas