New Georgia Island, Solomon Islands Photograph by Don Henry   Solomon Islands, east of New Guinea Tropical and Subtropical Moist Broadleaf Forests   13,900 square miles (35,900 square kilometers) -- about the size of New Hampshire and Connecicut combined Vulnerable

· Location and General Description
· Biodiversity Features
· Current Status
· Threats
· Ecoregion Justification
· References
More Photos

The Solomon Islands Rain Forests [AA0119] are true oceanic islands with high vertebrate endemism, including single-island endemics, restricted-range mammals, and an astounding sixty-nine bird species found nowhere else in the world. Large areas of naturally restricted lowlands below 400 m either have been or are under threat of logging or clearance for subsistence agriculture. Introduced cats have eliminated most native mammals on Guadalcanal.

Location and General Description

This ecoregion consists of tropical lowland and montane forests on Bougainville and Buka Islands in PNG and most of the island nation of the Solomon Islands (not including the Santa Cruz Group). The climate of the Solomon Island is tropical wet (National Geographic Society 1999). The islands are predominantly hill forest, although only small portions of a few of the islands extend beyond 1,000 m in elevation. The mountains on Guadalcanal reach past 2,000 m. The Solomons are the result of the subduction of the Australian tectonic plate beneath the Pacific tectonic plate, and the islands are a very active tectonic area. The surface geology of the islands consists predominantly of volcanic rocks, with some metamorphic rocks, uplifted coral islands (Rennell, Bellona, and Ontong Java), and recent (Pliocene to recent) alluvium in the lowlands. The islands increase in age from northwest to southeast (Mueller-Dombois and Fosberg 1998).

Mueller-Dombois and Fosberg (1998) outlined seven broad natural vegetation types in the ecoregion, including coastal strand vegetation, mangrove forests, freshwater swamp forests, two types of lowland rain forests, seasonally dry forest and grassland (only on Guadalcanal), and montane rain forest. Bougainville also contains floodplain forest, a transitional submontane rain forest, forest on ancient limestone, and vegetation on recent volcanic surfaces.

Coastal strand vegetation consists of mixed Spinifex-Canavalia containing Ipmoea, Spinifex, Canavalia, Thuarea, Cyperus, Scaevola, Hibiscus, Pandanus, Tournefortia, Cerbera, Calophyllum, Barringtonia, Terminalia, and Casuarina. Two types of mangrove vegetation are identified for the Solomons: a low forest dominated by Rhizophora apiculata and a tall forest dominated by Rhizophora spp. and Brugiera spp. Brugiera sexangula, B. parviflora, and Ceriops tagal reach their eastern limits in the Solomons. Most of the islands have large areas of freshwater swamp forest. Easily recognized subunits of freshwater swamp forest include Campnosperma brevipetiolata forests, closed-canopy Terminalia brassi forests, sago swamp (Metroxlyon solomonense), low-canopy Pandanus spp., and mixed swamp forest (Mueller-Dombois and Fosberg 1998).

The most widespread vegetation type is lowland rain forest. The canopy is uneven as a result of frequent natural disturbance (tropical storms, landslips, treefalls). The twelve most common tree species are Calophylum kajewskii, C. vitiense, Dillenia salomonensis, Elaeocarpus sphaericus, Endospermum medullosum, Parinari salomonensis, Maranthes corymbosa, Pometia pinnata, Gmelina mollucana, Schizomeria serrata, Terminalia calamansanai, and Campnosperma brevipetiolata. Whitmore (1974) recognized six lowland rain forest types, distinguished by whether the forest was on the northern or western side of the islands, elevation, and level of disturbance (Whitmore 1974; Mueller-Dombois and Fosberg 1998). Two groups of low-diversity lowland rain forest are recognized. The first group consists of monodominant forests of Campnosperma brevipetiolata (Santa Isabel, New Georgia, Choisel) or those with co-dominant C. brevipetiolata and Dillenia or C. brevipetiolata, Pometia pinnata, and Teysmanniodendron (Verbenaceae). It is thought that these forest types are related to disturbance. The second group of low-diversity forests is associated unusual soils, including limestone (Vitex cofassus and Pometia pinnata), flooding (Pterocarpus indicus and Terminalia brassi), or ultramafic soils (Casuarina papuana, Dillenia crenata, Syzygium, or Dacrydium) (Mueller-Dombois and Fosberg 1998).

Seasonally dry forest is found only on the leeward (north) side of Guadalcanal. These forests consist of mixed deciduous forest and Themeda australis grassland. The canopy is composed of Pometia pinnata, Vitex cofassus, and Kleinhovia hospita. The deciduous species are Pterocarpus indicus, Antiais toxicaria (Moraceae), Ficus spp., and Sterculia spp. The grassland probably is related to periodic burning by humans (Mueller-Dombois and Fosberg 1998).

The Fagaceae species that generally mark montane rain forest in the region (Castanopsis, Nothofagus, and Lithocarpus) are absent in the Solomons. Instead, a reduction in stature (from 25 to 35 m in the lowlands to 15 to 20 m in the uplands) is apparent. Syzygium, Metrosideros, Ardisia, Psychotria, Schefflera, Ficus, Rhododendron, Dacrydium, and Podcarpus pilgeri have been collected in the mountains of the Solomons (Mueller-Dombois and Fosberg 1998).

The outlying coral atolls support depleted lowland rain forest, remnant coastal and swamp vegetation, and Pandanus thickets. The vegetation is a product of generally poor soils combined with human alteration (Mueller-Dombois and Fosberg 1998).

Biodiversity Features

Overall richness and endemism in the Solomon Islands range from low to high when compared with those of other ecoregions in Indo-Malaysia. Bird and mammal endemism are high.

There is a clear difference between the mammalian faunas of the Solomon Islands and the Bismarck Archipelago and richer New Guinea to the west. Except for pteropodid bats, the Solomons and Bismarcks have many fewer mammals than New Guinea, and the Solomons, unlike New Britain, contain no marsupials. East beyond the Solomons there are even fewer mammal species. Almost all the mammal species have their origins in or via New Guinea (Flannery 1990).

Although the Solomon Islands contain only forty-seven mammal species, a remarkable twenty-six of those species are endemic or near endemic, including nine murid rodents (Melomys, Solomys, Uromys), fifteen pteropodid bats (Dobsonia, Melonycteris, Nyctimene, Pteralopex, Pteropus), a horseshoe bat (Anthops), and one molossid bat (Chaerephon) (Flannery 1995) (table 1). Three of the fruit bats-Bougainville monkey-faced bat (Pteralopex ancep), Guadalcanal monkey-faced bat (Pteralopex atrata), and montane monkey-faced bat (Pteralopex pulchra)-are critically endangered, and three of the rodents-Specht's mosaic-tailed rat (Melomys spechti), Poncelet's giant rat (Solomys ponceleti), and emperor rat (Uromys imperator)-are endangered (IUCN 2000; Wilson and Cole 2000; Flannery 1995).

Table 1. Endemic and Near-Endemic Mammal Species.

Family	Species
Pteropodidae	Melonycteris fardoulisi*
Pteropodidae	Melonycteris woodfordi*
Pteropodidae	Dobsonia inermis*
Pteropodidae	Nyctimene vizcaccia*
Pteropodidae	Nyctimene major
Pteropodidae	Pteralopex anceps*
Pteropodidae	Pteralopex atrata*
Pteropodidae	Pteralopex pulchra*
Pteropodidae	Pteralopex sp.*
Pteropodidae	Pteropus admiralitatum
Pteropodidae	Pteropus howensis*
Pteropodidae	Pteropus mahaganus*
Pteropodidae	Pteropus rayneri*
Pteropodidae	Pteropus rennelli*
Pteropodidae	Pteropus woodfordi*
Rhinolophidae	Anthops ornatus*
Molossidae	Chaerephon solomonis*
Muridae	Melomys bougainville*
Muridae	Melomys spechti*
Muridae	Solomys ponceleti*
Muridae	Solomys salamonis*
Muridae	Solomys salebrosus*
Muridae	Solomys sapientis*
Muridae	Uromys imperator*
Muridae	Uromys porculus*
Muridae	Uromys rex*

An asterisk signifies that the species' range is limited to this ecoregion.

Bird diversity drops off sharply from New Guinea as one moves east across the Pacific to the Solomons. Whereas New Guinea has seventy-one families and subfamilies of birds, the Solomons have forty-four. The Solomons are considered a center of bird endemism, with at least seven endemic genera. The dropoff in diversity seen in other animal groups as one moves east from New Guinea is also consistent with that seen in birds. Whereas New Guinea has seventy-one families and subfamilies of birds, and the Solomons have forty-four, Vanuatu has thirty-one (Keast 1996).

A total of 199 bird species inhabit the Solomons (Doughty et al. 1999). The Solomon Islands ecoregion has an almost exact correspondence with the Solomon group EBA (Stattersfield et al. 1998). This EBA contains more restricted-range bird species (seventy-eight) than any other EBA. Several of the islands, especially Makira (San Cristobal) and the New Georgia group, have their own endemic species and would qualify as important EBAs by themselves. The unique islands of Rennell and Bellona, separated from the rest of the Solomons by a submarine trench, are also an EBA, containing a total of twelve endemic species, and seven additional species. The atolls of Ontong Java, which are also part of this ecoregion, qualify as a Secondary Area because they provide habitat for an additional species, the atoll starling (Aplonis feadensis), which is also found off of small islands in the Bismarck Archipelago. Of these ninety-one restricted-range bird species, an incredible sixty-nine species are found nowhere else in the world; thus the Solomons are a global priority for bird conservation. Ninety species are endemic or near endemic (table 2). Three bird species are critically endangered: Makira moorhen (Gallinula silvestris), yellow-legged pigeon (Columba pallidiceps), and thick-billed ground-dove (Gallicolumba salamonis). Four additional bird species are endangered: imitator sparrowhawk (Accipiter imitator), Woodford's rail (Nesoclopeus woodfordi), chestnut-bellied imperial pigeon (Ducula rubricera), and white-eyed starling (Aplonis brunneicapilla) (Stattersfield et al. 1998; IUCN 2000). The Choisel pigeon (Microgoura meeki) was last reliably seen in 1904 and is presumed extinct (Stattersfield et al. 1998).

Table 2. Endemic and Near-Endemic Bird Species.

Family	Common Name	Species
Accipitridae	Imitator sparrowhawk	Accipiter imitator*
Accipitridae	Solomon sea-eagle	Haliaeetus sanfordi*
Accipitridae	Pied goshawk	Accipiter albogularis
Megapodiidae	Melanesian scrubfowl	Megapodius eremita
Rallidae	Woodford's rail	Nesoclopeus woodfordi*
Rallidae	Roviana rail	Gallirallus rovianae*
Rallidae	San Cristobal moorhen	Gallinula silvestris*
Columbidae	Yellow-bibbed fruit-dove	Ptilinopus solomonensis
Columbidae	Yellow-legged pigeon	Columba pallidiceps
Columbidae	Red-knobbed imperial-pigeon	Ducula rubricera
Columbidae	Crested cuckoo-dove	Reinwardtoena crassirostris*
Columbidae	Thick-billed ground-dove	Gallicolumba salamonis*
Columbidae	Choiseul pigeon	Microgoura meeki*
Columbidae	Silver-capped fruit-dove	Ptilinopus richardsii*
Columbidae	White-headed fruit-dove	Ptilinopus eugeniae*
Columbidae	Chestnut-bellied imperial-pigeon	Ducula brenchleyi*
Columbidae	Pale mountain-pigeon	Gymnophaps solomonensis*
Cacatuidae	Ducorps's cockatoo	Cacatua ducorpsii*
Loriidae	Cardinal lory	Chalcopsitta cardinalis
Loriidae	Yellow-bibbed lory	Lorius chlorocercus*
Loriidae	Meek's lorikeet	Charmosyna meeki*
Loriidae	Duchess lorikeet	Charmosyna margarethae*
Psittacidae	Singing parrot	Geoffroyus heteroclitus
Psittacidae	Finsch's pygmy-parrot	Micropsitta finschii
Cuculidae	Buff-headed coucal	Centropus milo*
Strigidae	Solomon hawk-owl	Ninox jacquinoti*
Strigidae	Fearful owl	Nesasio solomonensis*
Apodidae	Mayr's swiftlet	Aerodramus orientalis
Alcedinidae	Ultramarine kingfisher	Todirhamphus leucopygius*
Alcedinidae	Moustached kingfisher	Actenoides bougainvillei*
Pittidae	Black-faced pitta	Pitta anerythra*
Meliphagidae	Cardinal myzomela	Myzomela cardinalis
Meliphagidae	Bougainville honeyeater	Stresemannia bougainvillei*
Meliphagidae	Scarlet-naped myzomela	Myzomela lafargei*
Meliphagidae	Yellow-vented myzomela	Myzomela eichhorni*
Meliphagidae	Red-bellied myzomela	Myzomela malaitae*
Meliphagidae	Black-headed myzomela	Myzomela melanocephala*
Meliphagidae	Sooty myzomela	Myzomela tristrami*
Meliphagidae	Guadalcanal honeyeater	Guadalcanaria inexpectata*
Meliphagidae	San Cristobal honeyeater	Melidectes sclateri*
Pachycephalida	Mountain whistler	Pachycephala implicata*
Rhipiduridae	White-winged fantail	Rhipidura cockerelli*
Rhipiduridae	Brown fantail	Rhipidura drownei*
Rhipiduridae	Dusky fantail	Rhipidura tenebrosa*
Rhipiduridae	Rennell fantail	Rhipidura rennelliana*
Rhipiduridae	Malaita fantail	Rhipidura malaitae*
Monarchidae	Rennell shrikebill	Clytorhynchus hamlini*
Monarchidae	Bougainville monarch	Monarcha erythrostictus*
Monarchidae	Chestnut-bellied monarch	Monarcha castaneiventris*
Monarchidae	White-capped monarch	Monarcha richardsii*
Monarchidae	Black-and-white monarch	Monarcha barbatus*
Monarchidae	Kulambangra monarch	Monarcha browni*
Monarchidae	White-collared monarch	Monarcha viduus*
Monarchidae	New Caledonian flycatcher	Myiagra caledonica
Monarchidae	Steel-blue flycatcher	Myiagra ferrocyanea*
Monarchidae	Ochre-headed flycatcher	Myiagra cervinicauda*
Dicruridae	Solomon Islands drongo	Dicrurus solomenensis*
Corvidae	White-billed crow	Corvus woodfordi*
Corvidae	Bougainville crow	Corvus meeki*
Campephagidae	Melanesian cuckoo-shrike	Coracina caledonica
Campephagidae	Long-tailed triller	Lalage leucopyga
Campephagidae	Solomon cuckoo-shrike	Coracina holopolia*
Turdidae	New Britain thrush	Zoothera talaseae
Turdidae	Olive-tailed thrush	Zoothera lunulata*
Turdidae	San Cristobal thrush	Zoothera margaretae*
Sturnidae	Rennell starling	Aplonis insularis*
Sturnidae	Atoll starling	Aplonis feadensis
Sturnidae	Brown-winged starling	Aplonis grandis*
Sturnidae	San Cristobal starling	Aplonis dichroa*
Sturnidae	White-eyed starling	Aplonis brunneicapilla*
Zosteropidae	Louisiade white-eye	Zosterops griseotinctus
Zosteropidae	Rennell white-eye	Zosterops rennellianus*
Zosteropidae	Banded white-eye	Zosterops vellalavella*
Zosteropidae	Ganongga white-eye	Zosterops splendidus*
Zosteropidae	Splendid white-eye	Zosterops luteirostris*
Zosteropidae	Solomon Islands white-eye	Zosterops kulambangrae*
Zosteropidae	Kulambangra white-eye	Zosterops murphyi*
Zosteropidae	Yellow-throated white-eye	Zosterops metcalfii*
Zosteropidae	Grey-throated white-eye	Zosterops rendovae*
Zosteropidae	Malaita white-eye	Zosterops stresemanni*
Zosteropidae	Bare-eyed white-eye	Woodfordia superciliosa*
Sylviidae	Shade warbler	Cettia parens*
Sylviidae	San Cristobal leaf-warbler	Phylloscopus makirensis*
Sylviidae	Kulambangra leaf-warbler	Phylloscopus amoenus*
Sylviidae	Guadalcanal thicketbird	Megalurulus whitneyi
Sylviidae	Bougainville thicketbird	Megalurulus llaneae*
Dicaeidae	Midget flowerpecker	Dicaeum aeneum*
Dicaeidae	Mottled flowerpecker	Dicaeum tristrami*
Estrildidae	Bismarck munia	Lonchura melaena
Acanthizidae	Fan-tailed gerygone	Gerygone flavolateralis

An asterisk signifies that the species' range is limited to this ecoregion.

Buka, Bougainville, and the rest of the Solomon Islands (excluding the Santa Cruz Group) form a distinct and rather uniform phytogeographic unit. About a third of the Solomon Islands' flora is of Malesian (southeast Asian) origin, a third has Paleotropical origins, and a third is cosmopolitan, with a small Pacific contribution. There is a distinct break in floristic compositions with the nearby Bismarck Archipelago to the west, corresponding with the New Britain Trench that separates the submarine platforms. Two important Indo-Malayan tree families, Fagacae and Dipterocarpaceae, are not present in the Solomons. There are only about a dozen common tree species in the Solomons (Mueller-Dombois and Fosberg 1998).

Between November and April of each year the Solomon Islands are subject to tropical cyclones, which are an important source of natural disturbance to the islands' forests. Extreme droughts are also a natural event and occur irregularly at intervals of six to twenty years (Mueller-Dombois and Fosberg 1998).

Davis et al. (1995) identified two Centres of Plant Diversity on Bougainville Island: Mt. Balbi to southern coast, containing the largest stands of bamboo forest in Papuasia and remnant stands of Terminalia brassii, and Mt. Takuan-Tonolei Harbour, containing natural stands of Terminalia brassii and more than 1,000 vascular plant species.

Current Status

A large Australian-run copper mine was located in Bougainville, but it was shut down because of civil unrest several years ago. Introduced species are a special concern here, and most native mammals have been eliminated from Guadalcanal by cats. Hunting native species is common (Stattersfield et al. 1998,). Many bird species in the Solomons are vulnerable simply because of their small natural ranges (Stattersfield et al. 1998).

Only one protected area, 930 km² surrounding Mt. Balbi on Bougainville, exists in the ecoregion (table 3). A gap analysis, based on detailed vegetation and habitat type mapping, has never been performed to determine whether the existing protected area network adequately covers all habitats with protected areas that are large enough to maintain all critical ecological processes.

Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.

Protected Area	Area (km2)	IUCN Category
Mt. Balbi	930	?

Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

Types and Severity of Threats

Justification of Ecoregion Delineation

Distinct island groups were placed in their own ecoregions: the Solomon Islands Rain Forests [AA0119] and the Vanuatu Rain Forests [AA0126]. We followed Stattersfield et al. (1998) in delineating these ecoregions. MacKinnon (1997) did not extend his assessment beyond the island of Bougainville in the Solomon Islands. However, we followed Bouchet et al. (1995) and separated the distinctive dry forests in New Caledonia from the moist forests to delineate the New Caledonia Rain Forests [AA0113] and the New Caledonia Dry Forests [AA0202]. Stattersfield et al. (1998) did not show this distinction.

Udvardy (1975) placed all the ecoregions in the New Guinea and Melanesia bioregion, with the exception of New Caledonia, into the Papuan biogeographic province of the Oceanian Realm. New Caledonia was placed in the New Caledonian biogeographic province.

References

References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List

For more general information on this ecoregion, go to the WildWorld version of this description.