Tropical Rainforest Heritage of Solomon Islands

Date of Submission: 23/12/2008
Criteria: (vii)(ix)(x)
Category: Natural
Submitted by:
Ministry of Education and Human Resources Development
State, Province or Region:
Makira-Ulawa, Western, Choiseul and Guadalcanal Provinces
Ref.: 5416

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Property names are listed in the language in which they have been submitted by the State Party


Bauro Highlands of Makira-Ulawa Province - S10 38 E161 54

Mt. Maetambe region of Choiseul Province - S7 08 E156 57

Central caldera forests of Kolombangara of Western Province - S7 58 E157 4

Mt. Popomanaseu region of Guadalcanal Province - S9 42 E159 56

Mixed Cultural/Natural Property :

The Tropical Rainforest Heritage of Solomon Islands property is a natural serial site comprising representative tropical rainforest areas of Solomon Islands, including the Bauro Highlands of Makira-Ulawa Province, the central caldera volcanic skirt of Kolombangara in Western Province, the Mt. Maetambe area of Choiseul Province and the Mt. Popomanaseu area of Guadalcanal Province. The four sites that comprise the proposed property, which together cover over approximately 1500 km², are located within the Udvardy Papuan biogeographic province of the Oceanian realm.

Nearly three quarters of the global diversity of birds exists within 4.5% of the Earth's land area (Stattersfield et al. 1998). Within this small, intensely rich fraction of the planet's surface, no other area of comparable size holds more unique bird species than the Solomon Archipelago. Sandwiched between the depauperate avifauna of an expansive South Pacific and the rich continental biotas of the Australasian region, the birds of the Solomon Archipelago inhabit a biogeographic crossroads that has played a disproportionate role in influencing the development of classical biogeographic and speciation theory (see Mayr and Diamond 2001; Mayr 1942, MacArthur and Wilson 1967).

Of the 163 land birds that breed in the Solomon Islands, an astonishing 72 species (44% of Solomon Islands land birds) are found nowhere else in the world, while another 62 (38%) are considered unique subspecies. This represents the highest degree of avian endemism on an area basis on Earth. In addition to this rich avian endemism, the Solomon Islands rainforests also support numerous endemic amphibians, reptiles, molluscs,insects and several endemic plant groups reflecting unique patterns of speciation, isolation and dispersal.

The proposed properties are:

  • located within the Solomon Islands Rainforest Ecoregion, which forms part of the Solomon-Vanuatu-Bismarck Moist Forests - a WWF Global 200 Ecoregion
  • part of Conservation International's East Melanesian Islands Biodiversity Hotspot
  • considered a Centre of Plant Diversity, as part of the Bismarck Archipelago forests and those of nearby New Guinea

Floristically, the forests of Solomon Islands are related to Malesia, although there are fewer genera and species and the trees are generally smaller. While Solomon Islands vegetation generally exhibits low endemism relative to Western Melanesia, some plant groups exhibit high levels of endemism. More than 50% of the palm and orchid species, and 75% of climbing Pandanus species are endemic. The "ancient" plants such as the Winteraceae family are also of particular interest to scientists, with several species considered rare and endangered.

The forests of the Solomon Islands are comprised primarily of lowland and hill rainforest, with several broad vegetation types including coastal strand vegetation, mangrove forests, freshwater swamp forests, lowland rainforests, seasonally dry forest and grassland, and montane forest. One of the key features of interest is the high degree of compression in forest zones compared to larger and higher mountain ranges in nearby New Guinea. The montane rainforest zone occurs at altitudes as low as 700m on Kolombangara, Makira and Guadalcanal.

Rainforest dynamics in Solomon Islands rainforests are strongly influenced by natural disturbance, specifically cyclones, and successional patterns are influenced by the creation of gaps in the forest canopy. Human impacts, including 19th century large-scale taro field terracing, past settlement patterns, and traditional swidden agricultural practices have created a mosaic of secondary forest successions in many lowland forest areas.

The proposed property is within the Solomon Group Endemic Bird Area (EBA) which has more restricted range species than any other EBA in the world. The White-eye birds (Zosterops sp.) of the New Georgia Island group, including two species on Kolombangara, are considered a classic textbook example of speciation and island biogeography, with distinct species and sub-species occurring on each of the six major islands in this group.

Of the 47 mammals, 26 species of rodents and bats are endemic or unique sub-species. Reptiles and amphibians also exhibit high endemism. Of particular note is the Solomon Islands endemic Prehensile-tailed Skink (Corucia zebrata), the world's largest skink. Frogs show particularly high endemism at the genus level, while many other endemic species are likely to exist although the area is still poorly surveyed. Several endemic and unique sub-species throughout the proposed properties are critically endangered.

The sites of the proposed property are sparsely settled, with only a few small villages scattered throughout, notably along the coastal areas. The traditional landowners are subsistence agriculturalists and fishers who are highly dependant on the forests for their livelihoods. Of the 4500 plants present in Solomon Islands rainforests, over 600 are used by indigenous communities for food, housing materials, medicines and cultural uses (Henderson and Hancock, 1988). These forests have traditionally played, and continue to play, critical roles in defining and maintaining cultural identities of their traditional landowners.

Land is held under customary tenure throughout most of the proposed property. The one exception Kolombangara Island in Western Province, which is partly under government ownership.

Bauro Highlands of Makira Ulawa Province : The Bauro Highlands of the central Makira in Makira Ulawa Province contain some of the country's last extensive lowland forest tracts and an impressive range of endemic bird species. A dramatic southern coastline of rocky cliffs reach inland to the montane forest on some of the island's highest peaks at 1200m, encompassing full transitional gradients of forest zones. The Raro and Warihito River catchments are bounded by steep-sided wide valleys, with numerous streams and waterfalls and small perched floodplains as high as 400m in elevation. While this spectacular landscape provides some of the most dramatic rainforest vistas in the Solomons, it is the area's unusual ecology, influenced by its separation from the rest of the Solomons archipelago by deep water which results in its international significance. Makira's lowland and montane forest is home to 12 endemic bird species, as well as two endemic fig  species. The proposed property is approximately 630km2 in size, and with an increasing proportion of the area under a community-managed conservation area.

Kolombangara Island of Western Province :

The montane forest of Kolombangara Island in Western Province supports some of the richest bird communities of the New Georgia Groups islands, including at least two endemic species of bird as well as numerous unique forms of widespread Pacific species represented nowhere else in the Solomons. Additionally, it is likely that the rare and endangered Heinroth's shearwater (Puffinus heinrothi) and possibly Beck's petrel (Pseudobulweria becki) nest along the lush and inaccessible interior walls of the montane crater rim - nesting areas for both of these species have never been documented. The moss-covered montane forests of the central caldera support numerous rare Solomon Islands bird species such as the pale mountain pigeon (Gymnophaps solomonensis), the yellow-legged pigeon (Columba pallidiceps), Meek's lorikeet (Charmosyna meeki), and Mayr's swiftlet (Collocalia orientalis), as well as some widespread birds with poorly documented occurrence in the Solomons such as a probable resident form of the peregrine falcon (Falco peregrinus). Other vertebrate groups are sure to show similar or higher levels of endemism once surveyed, and frogs are already bearing this out with a spectacular new species of Platymantine frog currently being described from the island's elfin cloud forests. The forests of Kolombangara contain some of the oldest known survey plots in tropical rainforest and provide an important baseline for scientific research.

Mt. Maetambe area of Choiseul Province :

Mt. Maetambe region of central Choiseul is the best preserved example of forest growing on karst limestone in the Solomon Islands, covering the greatest altitudinal range from sea level to 800m. This 200 km2 area supports the principal rich lowland rainforest on Choiseul and supports a unique biodiversity, including at least seven endemic species of frog, and the endemic and endangered Poncelet's Giant Rat (Solomys Poncelti), the country's largest land mammal.

This limestone karst country has eroded overtime to form a distinctive landscape of caves with subterranean rivers, which are likely to be found to support more endemics after further survey. Further inland from coastline is the extinct volcano of Mt. Maetambe, whose past eruptions resulted in the cover of most of central Choiseul with lava and ash. These volcanic deposits of up to 600m thick form the high ridges that are drained to the south by the Vurulata river and the Kolombangara river to the north. A distinctive disturbed forest type inside the crater and in the montane forest covers these areas.

Mt. Popomanaseu area of Guadalcanal Province : Mt. Popomanaseu region of Guadalcanal Province, including its nearby forest catchments and the lowland valleys of the Itina River and its tributaries, includes a full forest community transition of lowland riverine forest to montane forest. Mt. Popomanaseu (2330m) and Mt. Makarakomburu (2249m) are the highest mountains in the country. The proposed property supports the largest contiguous area of montane forest the country, including forests on ultrabasic soils which may support as yet unidentified species. Above 1000m, mossy forest supporting podocarps and myrtle species is common, while endemic plant species and bird species are present. Mt. Popomanaseu is home to the only known endemic montane snail species in country. This 300km2 area has been subject to very limited survey, and further research is likely to uncover other areas of high conservation value.

Protection and Management :

WWF has developed a forests conservation programme to establish community-managed protected areas Choiseul, Kolombangara, and Guadalcanal, and to strengthen the existing community-managed protected area in Makira. Conservation International works in partnership with the Makira Community Conservation Foundation in supporting and expanding the existing protected area in the Bauro Highlands of Makira. Several community partnerships have also been developed on Kolombangara, Guadalcanal and recently Choiseul through cooperation with the American Museum of Natural History. There is a need to increase technical and financial support for these initiatives, and to develop national legislation to provide a legal basis for such protected areas and their traditional owners who wish to sustainably manage their land. The Ministry of Forests, Environment and Conservation aims to develop this legislation as part of the government's commitments under the Convention on Biological Diversity.

The majority of the intact forest on Kolombangara Island is in the process of being included in a Biodiversity and Customary Use Reserve collaboratively managed by local landowning communities and a local plantation timber company. Kolombangara Forest Products Ltd remains a model for sustainable tropical forest management in the South Pacific, and has established several reserve areas within their forest management area. The company works in cooperation with the American Museum of Natural History and WWF to support the development of protected areas on the island.

Justification of Outstanding Universal Value

The proposed Tropical Rainforest Heritage of Solomon Islands is a serial property comprising four components. They contain globally outstanding biodiversity and have an exceptional proportion of endemic plant and animal species. The level of endemism within the property is approximately 50-75% for several groups, and endemic families and genera are common. The serial property comprises a representative selection of the most important habitats of the unique rainforest biota of the Solomon Islands, including many threatened and endemic plant and animal species.

The proposed properties are areas of exceptional of natural beauty comprising rainforest covered extinct volcanic craters, large tracts of lowland rainforest with sweeping vistas, rugged valleys and deeply incised gorges with numerous rivers and waterfalls, and dramatic coastlines.

The proposed properties demonstrate classic examples of island biogeographic patterns and some of the most extreme geographic differentiation among island vertebrates, including histories of speciation and dispersal. The isolation of the Solomon Islands archipelago from neighbouring landmasses has resulted in globally outstanding avian communities that are unparalleled anywhere else on earth, internationally significant plant communities, and high levels of faunal endemism.

Makira Island and the New Georgia Island Group in particular are noted bird conservation priorities within the Solomon Islands for their high numbers of endemic species, while both these islands and Guadalcanal also have high numbers of restricted range species. Choiseul and Guadalcanal support several threatened tree species. Collectively these properties are the best representative examples of the rainforests of Solomon Islands and are home to both rare and endangered species.

Statements of authenticity and/or integrity

The proposed property includes full transitional gradients from sea level to montane forests. Bauro Highlands of Makira, Mt. Maetambe in Choiseul and Mt. Popomanaseu in Guadalcanal all represent some of the most intact montane and lowland forest areas in the country. On Kolombangara, much of the lowland forest (below 400m) has been cleared for plantations although relatively large tracts of lowland rainforest still connect the montane forest to the coastal areas throughout the plantations providing corridors to the coastlines, including along the Vila river catchment.

While the areas are not functionally linked, as a group these properties are considered some of the best representative examples of the exceptional terrestrial biodiversity of the Solomon Islands, in particular its avian and faunal diversity. The most unique element of the living diversity of the Solomon Islands - extreme inter-island variation among its fauna - requires disjunct representation by its very nature. Further, the WH Operational Guidelines define natural serial properties as:

  •  "the same type of property which is characteristic of the geographical zone;
  •  the same geological, geomorphological formation, the same biogeographic province, or the same ecosystem type"

The four sites that comprise this proposed property, while having ecosystem variability, are characteristic of eastern Melanesia and representative of the eastern insular component of the Papuan biogeographic province.

Comparison with other similar properties

In its description of the East Melanesian Biodiversity Hotspot, Conservation International (2007) notes:

"Because most of the islands of this hotspot have never been in land contact with New Guinea, their fauna and flora are a mix of recent long-distance immigrants and indigenous lineages derived from ancient Pacific-Gondwanaland species. Thus, the hotspot contains classic examples of relatively recent adaptive radiation typical of oceanic islands, such as the white-eyes (family Zosteropidae) and monarch flycatchers (family Monarchidae), but also carries some odd colonizers from times past such as the giant prehensile-tailed skink (Corucia zebrata), whose closest living relatives are the blue-tongued skinks (genus Tiliqua) of Australia, New Guinea, and Indonesia. The East Melanesian Islands Hotspot also has affinities with Fiji (included as part of the Polynesia-Micronesia Hotspot), such as the Platymantis frogs, ancient "monkey-faced" fruit bats of the genus Pteralopex, and Nesoclopeus rails....The isolation of many of the islands and local adaptive radiation have led to very high levels of endemism, with numerous species endemic to the hotspot and many others endemic to subsets of the hotspot or even confined to single islands."

In this context the proposed property contains the best representative examples of lowland and montane rainforests of the Solomon Islands, including the areas that offer the best chance of conservation of a representative and distinctive biodiversity that is found nowhere else on earth. On an area basis, the avian endemism of the proposed property is unmatched internationally, while mammalian and amphibian diversity is also of particular importance though more survey work is needed to assess this. The Solomon Islands has a higher faunal diversity and endemism than any other Pacific island nation except Papua New Guinea.

Precedent already exists for WH listing of forest serial sites: the Gondwana Rainforests of Australia (previously Central Eastern Rainforest Reserves) WH Site and the Tropical Rainforest  Heritage of Sumatra. In both cases a geographically separate series of protected areas form the WH property: 50 reserves in the Australian example and three national parks on Sumatra. In addition, the Wet Tropics of Queensland WHA in Australia is comprised of over 730 separate parcels of land including national parks, State forest, freehold land and a range of leases over public land. Many of the government-owned reserves are geographically separated.

Of particular comparative value is Madagascar's Rainforests of the Atsinanana WHA listed in 2007, which comprises six national parks distributed along the eastern part of the island. The justification for inscription states that "these relict forests are critically important for maintaining ongoing ecological processes necessary for the survival of Madagascar's unique biodiversity". Although the endemism and biodiversity in Madagascar is higher on a global basis, these remaining unlogged and/or uncleared forest areas of the Solomon Islands are of equally outstanding conservation value for the survival of the country's unique biodiversity in the context of the western Pacific and eastern Melanesia.

Any comparative analysis of the natural terrestrial values of oceanic properties needs to take into account the characteristics of Pacific island biogeography. That is, the generally west to east gradient of decreasing diversity and increasing endemism from Southeast Asia to the oceanic islands of the Pacific. It is difficult to compare, therefore, outstanding species diversity values between the "megadiverse" countries and larger sites and the Solom on Islands. However, even in this context the proposed properties have outstanding value. For example, the Solomon Island forests have 4,500 species of plants and are recognised as one of the world's great Centres of Plant Diversity rich in unique palms, orchids and climbing pandanus, and 25 tree species are threatened. This compares with the 2,984 plant species in Madagascar, 1,625 species in the Gondwana Rainforests of Australia WHA and 2,500 species in the 6,000 km² Dong Phayayen-Khao Yai Forest Complex of Thailand. Avian endemism is clearly an outstanding value of the proposed property, and the Solomon Islands 72 endemic bird species compare favourably with the 35 endemic birds in the 25,000 km² Lorentz National Park WHA in Indonesia (also in the Papuan biogeographic province), 21 species in the 25,000 km² Tropical Rainforest Heritage of Sumatra and the 13 species in Wet Tropics of Queensland WHA.

In the context of the historically diminished and highly threatened living diversity of the tropical Pacific, the Solomon Islands are the last great oceanic archipelago still maintaining a rich compliment of its natural heritage on a truly inter-island scale.