Location and General Description
The more than 300 islands of Fiji are located 3,000 km east of Australia at 16-20 o S latitude and 178 E-178o W longitude. The islands of Viti Levu and Vanua Levu occupy 78% of the land area in Fiji and support the tallest mountain at 1323 m. Most islands are the remnants of once active volcanoes siting on a piece of the Pacific Plate drifting slowly southeast through an extensive zone of fracturing, volcanism, and shearing resulting from the subduction of the Pacific Plate under the Australian Plate (Mueller-Dombois & Fosberg 1998). The oldest terrestrial areas have probably been exposed for 5-20 million years but the youngest island, Taveuni, last erupted 2000 years ago (Doyle and Fuller 1998). Most soils are derived from volcanic material, but some are comprised of uplifted marine reefs and sediments and rivers on older islands have formed alluvial plains of sedimentary soils (Ash 1992).
The climate is tropical with mean monthly temperatures ranging from 22o C in July to 26o C in January and little seasonality in rainfall (Ash 1992). Most areas receive over 2,500 mm of rain per year and because of the islands’ exposure to southeasterly winds, rainfall increases with elevation on the southeast facing slopes with rainfall peaks of 5000-10000 mm per year on mountains (Ash 1992). Cyclones occasionally hit the islands between January and April. Northwest slopes at low to moderate elevations are often in the rain shadow of mountains and experience drought in winter; these areas are dominated by tropical dry forest.
The 274 km2 Wallis and Futuna Islands lie approximately 400 km northeast of the main islands of Fiji at 13-14 o S latitude and 176-178 o W longitude (Dupon 1986, Stattersfield et al. 1995). The three islands in the group, Uvea, Futuna, and Alofi, are extinct and deeply eroded volcanoes although once active craters are still visible on Uvea. Futuna and Alofi, 200 km to the east, are older with limestone terraces indicating previous higher sea levels. Uvea has an extensive barrier reef with exposed coral keys and volcanic islets. Annual rainfall in the Wallis and Futuma Islands is similar to that of Fiji with 2,500-3,000 mm falling per year (Mueller-Dombois and Fosberg 1998). Rotuma is a volcanic island (47 km2, 250m high) lying 500 km north of Fiji. It was once covered in tropical moist forest that has almost been entirely replaced by coconuts and shifting crops (Clunie 1984, Stattersfield et al. 1995, Mueller-Dombois & Fosberg 1998).
Moist tropical forest occurs as lowland rain forest, montane rain forest, and cloud forest in Fiji, Rotuma, and Wallis and Futuna. Common tree species in lowland forest include Degeneria vitiensis, Pandanus joskei, Myristica macrantha, Endiandra gillespiei, Agathis macrophylla, Calophyllum vitiense, Canarium vitiense, Calophyllum neo-ebudicum, Syzygium spp., and Garcinia myrtifolia (Kirkpatrick & Hassall 1985). On Wallis and Futuna other common trees include Rhus taitensis, Elaeocarpus angustifolia, Elaeocarpus tonganus, Planchonella spp., Pometia pinnata, and Myristica fatua (Mueller-Dombois and Fosberg 1998). Montane rain forests are found in wind-exposed areas above 400-600 m where temperatures are 4-6 o C lower than the on the coast. This wind-swept and stunted forest is dominated by Agathis vitiensis, Podocarpus spp., Calophyllum vitiense, Endospemum macrophyllum, Myristica castaneifolia, Dysoxylum spp., and Metrosideros collina (Mueller-Dombois & Fosberg 1998).
Cloud forest occurs occupies about 50-100 km2 scattered above 600-900 m on the ridges and peaks of Fiji’s largest islands and on the 765 m summit of Mount Singavi, Futuna Island. Typically rainfall in these areas exceed 4500 mm per year and temperatures range from 10-20 o C (Ash 1987). This extremely dense forest has a canopy of about 7 m is dominated by tree ferns (Cyathea spp.), Dysoxylum gillespianum, Hernandia moerenhoutiana, Fagraea spp., Syzygium spp., Macaranga seemannii, and Leptopteris ferns with an abundance of climbing Freycinetia spp. (Mueller-Dombois & Fosberg 1998).
The tropical moist forests of Fiji support a particularly rich fauna and flora relative to other oceanic island groups in the Pacific. The forests of Fiji are notable for a large number of endemic species and higher taxa. The many primitive plant taxa, including an endemic family of tree, the Degeneraceae, belie the ancient origins of the biota. The islands of Fiji have a complex geologic history spanning at least 40 million years. Under the influence of seafloor spreading and the formation and migration of oceanic arc-trench complexes, the location of the island group has varied significantly from the Eocene to the present. The Tongan Island of ‘Eua, originally part of the Gondwana supercontinent, probably came into contact with Viti Levu about 5 million years ago, and some Gondwanan plant taxa may have been transferred at that time. Viti Levu and ‘Eua still share the Gondwanic gymnosperm genus, Podocarpus. The bulk of the present-day flora, however, shows strong links with the Malesia-Asia region. Approximately 90 percent of Fiji’s 476 genera of flowering plants are also found in New Guinea, and 65 to 75 percent also occur in Australia and New Caledonia (WWF & IUCN 1995). Most of the flora was probably established by long-distance dispersal, especially by frugivorous birds or bats, along the island arcs of Melanesia (Ash 1992).
The tropical moist forests of Fiji, Rotuma, and the Wallis and Futuna Islands contain an rich diversity of flowering plants, unique palm species and endemic frogs, lizards, snakes, and birds including many single island endemics. There are 1,769 vascular plants native to Fiji with about 23% endemism; many of the remaining species are regional endemics shared with Samoa, Tonga and Vanuatu (Ash 1992, WWF & IUCN 1995). Approximately 1,350 vascular plant species are found in moist tropical forest (Smith 1979). Many plant genera reach the eastern limit of their distribution in Fiji (Doyle & Fuller 1998). Fiji is notable for having an endemic family of primitive tree, the Degeneraceae, distantly related to magnolias. There are two species, Degeneria vitiensis and D. roseiflora. Other primitive plants include the cycad, Cycas rumphii, and the giant Agathis macrophylla and Dacrydium nausoriense (Ryan 2000). A number of Fiji’s 10 gymnosperm species are considered endangered including the endemics Podocarpus affinis, Acmophyle sahniana, and Dacrydium nausoriense (Doyle 1998). All of Fiji’s 24 native palm species are endemic making Fiji a biodiversity hotspot for palms (Doyle & Fuller 1998). At least 8 of these palms are considered endangered or critically endangered, including Neoveitchia storckii, an endemic monotypic genus, now restricted to a single population of less than 200 plants on Viti Levu (Gorman & Siwatibau 1975, Doyle & Fuller 1998). Plant distributions can be quite localized. For example, Mount Kasi on Vanua levu had 8 species restricted to it (Davis et al. 1995). Futuna Island supports 3 endemic plant species.
Fiji is the eastern-most limit of natural amphibian distributions in the tropical Pacific. Endemic species include the Fiji Ground Frog (Platymantis vitianus) and the Fiji Tree Frog (Platymantis vitiensis) (Ryan 2000). One terrestrial snake, Ogmodon vitiensis, is an elapid with ancient origins. Fiji has 27 native passerines including 4 endemic species and 3 parrots, 4 pigeons, and a rail that are all endemic (Langham 1989). The striking crested and banded iguanas (Brachylophus vitiensis and B. fasciatus) are both endemic. These unusual iguanas are believed to be derived from Neotropical ancestors, many thousands of kilometers across the Pacific. Only Fiji and Tonga are known to support iguanas in the Pacific (except for the Galapagos Islands which are quite near South America).
Many species in Fiji are restricted to one or to only a few islands, making them more vulnerable to human disturbance. The Fiji petrel (Pseudobulweria macgillivrayi) is an endangered species that was originally collected in 1855 and not seen again until 1994 when a small breeding population was discovered in cloud forest on Gau Island (Watling 1986). The silktail (Lamprolia victoriae) represents an endemic genus of monarch flycatcher and is restricted to the islands of Taveuni and Vanua Levu (Olson 1980, Stattersfield et al. 1998). The orange dove (Ptilinopus victor), golden dove (P. luteovirens), and whistling dove (P. layardi) are spectacularly beautiful fruit-doves, each limited to a different set of islands. The long-legged warbler (Trichocichla rufa) and the bar-winged rail (Rallus poecilopterus) were restricted to Viti Levu and Vanua Levu, but may be extinct. Other localized endemics include the spectacular Fijian iguanas (Brachylophus fasciatus and B. vitiensis), the monkey-faced fruit bat (Pteralopex acrodonta), mastiff bat (Tadarida jobensis), pink-billed parrotfinch (Erythrura kleinschmidti), Peale’s pigeon (Ducula latrans), and red-throated lorikeet (Charmosyna amabilis). The Wallis and Futuna Islands have endemic land snails and 5 endemic bird subspecies (Gill 1995).
Limited archeological work suggests that even more species were present in Fiji, and Wallis and Futuna prehistorically. Discovered so far are a giant pigeon (Ducula david), two species of megapode, a giant land iquana, a 3 m land crocodile, a giant frog (Discodeles guppyi), a large horned tortoise (Myolania sp) (Balouet & Olson 1987, Ryan 2000). Most of these are believed to have gone extinct shortly after the arrival of the first humans on the island, perhaps due to overhunting.
Fiji and Wallis and Futuna were settled by Polynesians and Melanesians between 3300 and 4000 years ago. About 80% of the population lives on Viti Levu but it is growing rapidly on all main islands (Ash 1992). About 40% (7570 km2) of land area of Fiji remains covered in some type of tropical moist forest (Kirkpatrick & Hassall 1985). Since the 1960’s about 15 % of forest have been completely cleared and selective logging is have removed much of the standing diversity in accessible forest by about 2020 leaving approximately 2700 km2 of old growth forest in steep and inaccessible areas (Ash 1992). Most areas of the Wallis and Futuna islands have been deforested and heavily eroded with about 15% of forest remaining on Uvea and 30% on Futuna, mostly above 400 m and at the heads and on the steep slopes of deep valleys. Rotuma has been entirely deforested and support secondary vegetation (Stattersfield et al. 1998).
In Fiji, approximately 68 km2 of moist forest is currently protected in reserves including Mount Tomaniivi Nature Reserve, Viti Levu which is the only reserve containing cloud forest (Watling 1986). This reserve system protects less than 1 % of remaining forests and there is a strong need for reserves on islands other than Viti Levu and Vanua Levu to protect regional endemics. In particular, Mt. Washington, Kadavu island has substantial areas of native forest left and a large seabird breeding colony near its summit, Ovalau and Rotuma Islands supports intact lowland rain forest, and Taveuni Island has montane rainforest supporting endemic birds (Dahl 1980). Reserves on Viti Levu and Vanua Levu need to be enlarged so that they enclose viable populations of flora and fauna (Dahl 1980). In Wallis and Futuna, uninhabited Alofi Island is one of the least disturbed high islands in the Pacific (Mueller-Dombois and Fosberg 1998).
Types and Severity of Threats
The principle threat to forests in the ecoregion is logging and subsequent development of logged areas for plantations or agriculture such that in the near future isolated patches of forest may be restricted to isolated ridgelines, mountain tops, and areas unsuitable for human use. Alien species also represent a major threat to the Fijian biota. Mongoose, cats, pigs, and rats are efficient predators on native birds, reptiles, amphibians, and invertebrates, causing greatly diminished populations or extirpation on islands. Taveuni is the largest island without mongoose at this point, and Gau is still free of feral pigs. Both islands may act as important refugia for vulnerable native species. Introduced plants, such as Psidium guajava, Lantana camara, and Mikania micrantha are serious weeds degrading natural communities.
Justification of Ecoregion Delineation
This ecoregion includes the main Fijian islands of Vanua Levu, Viti Levu, Taveuni, and their satellites, as well as Rotuma, Wallis and Futuna. Allison (1996) treats the Fiji Islands as a unit herpetologically. Two species of Emoia skinks link Rotuma with the rest of Fiji. There are 24 bird species confined to the Fiji Islands, and Birdlife International (Stattersfield et al. 1998) has delineated these islands as an Endemic Bird Area. Rotuma, though it contains one endemic birds species, shares bird affinities with the rest of Fiji. Wallis and Futuna share bird species with both Fiji and Samoa, and thus have no clear affinity with either island group. Van Balgooy (1996) lumps the main Fiji Islands as a floristic unit and includes Rotuma, Wallis and Futuna in the same unit, albeit with weaker floristic affinities. We have delineated the Fiji Islands (including Rotuma, Wallis and Futuna) as one ecoregion.
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Prepared by: Tim Male
Reviewed by: In process