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Southeastern Asia: Philippines

The Greater Negros-Panay Rain Forests [IM0114] ecoregion, including the Western Visayas and parts of additional political regions, appears as a number of isolated islands, but during the last ice ages these islands were (for the most part) part of one continuous island. The islands contain a unique mix of Sundaic and Philippine mammals and birds, including leopard cats and endemic pigs and deer species. Sibuyan, a small mountainous island surrounded by deep water, contains five endemic mammals and several restricted-range birds and nearly qualifies as an ecoregion in itself. 

  • Scientific Code
    (IM0114)
  • Ecoregion Category
    Indo-Malayan
  • Size
    13,500 square miles
  • Status
    Critical/Endangered
  • Habitats

 Location and General Description

The ecoregion includes the large island of Negros, Panay, and Cebu and the smaller islands of Masbate, Ticao, and Guimaras; Sibuyan, Romblon, Tablas, and Siquijor are moderately isolated and distinctive (Heaney and Regalado 1998). The climate of the ecoregion is tropical wet (National Geographic Society 1999). The Visayas receive approximately 2,419 mm of rainfall annually. July and August are the wettest months. The west coasts of Panay and Negros experience a dry season between November and February (Davis et al. 1995).

Most of these islands have been uplifted above water in the last 6 million years or less (Hall and Holloway 1998). Sibuyan Island contains pre-Tertiary schists, marble, volcanics, and ultramafics (Davis et al. 1995). Cebu contains a rugged mountain spine, and 73 percent of the island contains slopes greater than 18 percent. The geology of Cebu includes limestones, marls, and karst topography (Wood et al. 2000). Negros contains a string of volcanic mountains (Wood et al. 2000).

The channel between Greater Negros-Panay and the surrounding islands of Luzon and Greater Mindanao is more than 120 m deep. During the last ice age (late Pleistocene), sea level was approximately 120 m below current levels and Greater Negros-Panay was separated from ice age Luzon and the Eastern Visayas by a narrow channel (Heaney 1986). Except for the eastern portion of Panay and much of Masbate, the islands generally are fairly rugged, with the highest elevation being 2,465 m Mt. Canlaon in north-central Negros.

Vegetation types in the ecoregion are diverse and include beach vegetation, mangroves, tropical lowland rain forest, montane forests, and grasslands and heath forests. Beach forest merges with other forest types away from the coast and includes Casuarina and Barringtonia mixed with other lowland species. Palms, vines, bamboo, and Pterocarpus indicus are present only in rare back-beach swamps. This habitat type is extremely rare because of coastal habitation (Davis et al. 1995; Dickinson et al. 1991).

The lowland evergreen dipterocarp rain forest was once the dominant vegetation of the ecoregion and contained Dipterocarpus spp., Shorea spp., Hopea spp., Pterocarpus indicus, and pandans (Davis et al. 1995). Philippine dipterocarp forest is quite tall (45-65 m) and dense, with three layers of canopy. Lianas and bamboo are rare in mature forest but common in poorly developed evergreen forest. Ferns, orchids, and other epiphytic plants are found on the larger trees. At higher elevations there are only two canopy layers, tree stature is lower, and there are more epiphytes. Upper hill dipterocarp forest is found at elevations of 650-1,000 m and contains dominant Shorea polysperma and oaks, chestnuts, and elaeocarps. At approximately 1,000 m the montane forest contains oaks and laurels (Heaney and Regalado 1998). The mossy upper montane forest generally is found at elevations over 1,200 m, where humidity is constantly high. This stunted, single-story moss- and epiphyte-covered forest contains tree ferns up to 10 m high. (Dickinson et al. 1991).

 

 Biodiversity Features

Greater Negros-Panay contains a unique mix of Sundaic and Philippine mammals and birds, including leopard cats and endemic pig and deer species. Fifty-eight mammals inhabit the ecoregion, and thirteen mammal species are endemic or near endemic (table 1). Six of these species (Crocidura mindorus, two Apomys spp., and Chrotomys, Tarsomys, and Haplonyteris spp.) are limited to Sibuyan Island within the ecoregion (Crocidura mindorus is also found on Mindoro); most of these species have yet to be named. Two endemic large vertebrates are especially notable: the Philippine spotted deer (Cervus alfredi) and the Visayan warty pig (Sus cebifrons). The Visayan warty pig is critically endangered, and the Philippine spotted deer is endangered (IUCN 2000). One found only on Negros and Cebu, the Philippine bare-backed fruit bat (Dobsonia chapmani), is now believed to be extinct because of guano mining, deforestation, and hunting (Heaney et al. 1998).

Table 1. Endemic and Near-Endemic Mammal Species.

Family
 Species
 
Sorcidae
 Crocidura mindorus
 
Sorcidae
 Crocidura negrina*
 
Muridae
 Apomys sp. A*
 
Muridae
 Apomys sp. B* (Sibuyan only)
 
Muridae
 Apomys sp. C* (Sibuyan only)
 
Muridae
 Chrotomys sp. A* (Sibuyan only)
 
Muridae
 Crateromys heaneyi*
 
Muridae
 Tarsomys sp. A* (Sibuyan only)
 
Pteropodidae
 Nyctimene rabori*
 
Pteropodidae
 Dobsonia chapmani*
 
Pteropodidae
 Haplonycteris sp. A* (Sibuyan only)
 
Suidae
 Sus cebifrons*
 
Cervidae
 Cervus alfredi*
 

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

Sibuyan, a small mountainous (to 2,052 m) island surrounded by deep water within the ecoregion, is outstanding in itself. Sibuyan contains six endemic mammals (five strict endemics; Heaney et al. 1998; Heaney and Regalado 1998; Goodman and Ingle 1993) and is considered a Secondary Area by BirdLife International (Stattersfield et al. 1998) because of the existence of three restricted-range birds. These restricted-range birds are also found elsewhere but have no clear affinities. One hundred thirty-one bird species have been recorded on the island, a high number for an isolated island of only 463 km2. Sibuyan still contains about half of its original forest cover (100-150 km2), including some extremely rare (in the Philippines) lowland forest; unfortunately, logging threatens the remainder (Goodman and Ingle 1993; Stattersfield et al. 1998). Sibuyan Island is also a Centre of Plant Diversity (CPD) (Davis et al. 1995), containing beach vegetation, mangroves, lowland rain forest, montane forests, and grasslands and heath forests. There are an estimated 700 vascular plant species on the island, including 54 endemic species. The flora is closely related to that of Luzon. Sibuyan contains valuable timber trees, almaciga (Agathis philippensis) resins, and ornamental plants and has good potential for tourism (Davis et al. 1995).

The Asian leopard cat (Prionailurus bengalensis), an Asian species, is found on Negros, Panay, and Cebu within the ecoregion. Also found on Palawan, the Negros leopard cat is a subspecies (Heaney et al. 1998). Threatened endemic or near-endemic mammals include the critically endangered Negros shrew (Crocidura negrina) and Philippine tube-nosed fruit bat (Nyctimene rabori), the endangered Mindoro shrew (Crocidura mindorus) and Panay bushy-tailed cloud rat (Crateromys heaneyi), and the widespread but endangered golden-crowned fruit bat (Acerodon jubatus) (IUCN 2000).

The Visayan warty pig has been extirpated from Masbate, Guimaras, Cebu, and Siquijor and now lives only in isolated areas of Negros and Panay, where hunting of them is still intense. There are no effective protected areas in the fragmented range of S. cebifrons. The Visayan warty pig is smaller than its closer relative, the Philippine warty pig (Sus philippensis), which the IUCN considers rare and declining. The Visayan warty pig once inhabited both lowland and montane rain forests and may have thrived in disturbed areas as well (Oliver 1993).

The Philippine spotted deer (Cervus alfredi) has been extirpated from Guimaras, Cebu, and Siquijor and is now limited to the Mt. Madja-Mt. Baloy area of west Panay and some scattered forest fragments on Negros. A very small population apparently was located on Masbate in 1991. Small populations are protected in Mt. Canlaon National Park, North Negros Forest Reserve, and the Mount Talinis/Lake Balinsasayao Reserve. The Philippine spotted deer prefers dipterocarp rain forests but also frequents open grassland patches and secondary forest. The population has been reduced by habitat loss and hunting, which are still the main threats (Wemmer 1998).

The Greater Negros-Panay ecoregion encompasses two EBAs (Negros and Panay; Cebu) and two Secondary Areas (Tablas, Romblon, and Sibuyan; Siquijor). There are seventeen restricted-range bird species in the Negros and Panay EBA, six restricted-range species in Cebu (five additional species), and several others in the adjacent Secondary Areas. A total of twenty-three endemic or near-endemic species are found in the ecoregion (Kennedy et al. 2000; table 2). An extremely high proportion of these birds are threatened. These include the critically endangered Negros bleeding-heart (Gallicolumba keayi), Negros fruit-dove (Ptilonopus arcanus), Tarictic hornbill (Penelopides panini), writhed-billed hornbill (Aceros waldeni), white-throated jungle flycatcher (Rhinomyias albigularis), scarlet-collared flowerpecker (Dicaeum retrocinctum), Cebu flowerpecker (Dicaeum quadricolor), and twelve endangered restricted-range bird species (Stattersfield et al. 1998). Almost no forest remains on Cebu, and the species with these habitats on Cebu are in a critical situation.

Table 2. Endemic and Near-Endemic Bird Species.

Family
 Common Name
 Species
 
Turnicidae
 Spotted buttonquail
 Turnix ocellata
 
Columbidae
 Negros bleeding-heart
 Gallicolumba keayi*
 
Columbidae
 Negros fruit-dove
 Ptilinopus arcanus*
 
Strigidae
 Mantanani scops-owl
 Otus mantananensis
 
Apodidae
 Philippine needletail
 Mearnsia picina
 
Bucconidae
 Tarictic hornbill
 Penelopides panini*
 
Bucconidae
 Writhed-billed hornbill
 Aceros waldeni*
 
Monarchidae
 Celestial monarch
 Hypothymis coelestis
 
Campephagidae
 Blackish cuckoo-shrike
 Coracina coerulescens
 
Campephagidae
 White-winged cuckoo-shrike
 Coracina ostenta*
 
Irenidae
 Philippine leafbird
 Chloropsis flavipennis
 
Muscicapidae
 Negros jungle-flycatcher
 Rhinomyias albigularis*
 
Muscicapidae
 Ash-breasted flycatcher
 Muscicapa randi
 
Muscicapidae
 Black shama
 Copsychus cebuensis*
 
Pycnonotidae
 Streak-breasted bulbul
 Ixos siquijorensis*
 
Timaliidae
 Flame-templed babbler
 Stachyris speciosa*
 
Timaliidae
 Panay striped-babbler
 Stachyris latistriata*
 
Timaliidae
 Negros striped-babbler
 Stachyris nigrorum*
 
Estrildidae
 Green-faced parrotfinch
 Erythrura viridifacies
 
Dicaeidae
 Cebu flowerpecker
 Dicaeum quadricolor*
 
Dicaeidae
 Visayan flowerpecker
 Dicaeum haematostictum*
 
Dicaeidae
 Scarlet-collared flowerpecker
 Dicaeum retrocinctum
 
Lanidae
 Grey-capped shrike
 Lanius validirostris
 

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

The critically endangered Philippine crocodile (Crocodylus mindorensis) was historically found on the islands of Luzon, Mindoro, Masbate, Samar, Jolo, Negros, Busuanga, and Mindanao, but the only remaining populations are found on Mindoro, Negros, Mindanao, and Busuanga. Whereas the decline of the species initially was driven by overexploitation, habitat loss and human persecution are now the principal threats to the Philippine crocodile. Surveys in 1980-1982 revealed a total wild population of approximately 500-1,000 individuals, but current wild populations may be approximately 100 nonhatchlings. Captive breeding efforts are being led by the Crocodile Farming Institute, an entity of the Philippine government (Ross 1998; IUCN 2000).

 Current Status

"Nowhere in the Philippines is environmental degradation quite so acute, and the need for immediate conservation action quite so pressing, as in the West Visayas, or Negros Faunal Region" (Oliver 1993, p. 151). This ecoregion harbors the some of the highest levels of endemism but has suffered a disproportionate share of deforestation, and to compound the problem the area is underrepresented in the national protected area system (Oliver 1993).

The Philippines were once almost completely forested (Dickinson et al. 1991), but forests have been significantly reduced in this ecoregion and the rest of the Philippines. Aerial surveys indicate that Sibuyan Island still contains substantial areas of closed-canopy forest. Forests on Masbate Island have been devastated by improper farming and pasture practices. Remaining closed-canopy forests on Panay straddle the main mountain range. Open-canopy dipterocarp forests can still be found on Panay in steep areas at elevations between 690 and 2,150 m. Closed-canopy forests can also be found on Negros. Mt. Canlaon contains broadleaf and mossy forest on steep slopes at elevations of 490 to 1,870 m; there was little to no buffer zone between this forest and cultivation in 1992. On Mt. Mandalagan, remaining mossy forest is surrounded by a large buffer of residual open-canopy forest. A patch of closed canopy forest also remains above Dumaguete City in Negros (Development Alternatives 1992). In 1988, Negros was only 4 percent forested and Panay was 8 percent forested (SSC 1988).

Cebu contains approximately 15 km2, or 0.3 percent, of its original dipterocarp forest cover (SSC 1988; Brooks et al. 1995); this has led to the near extinction of the island's endemic species. Little of the ecoregion is protected (table 3).

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

Protected Area
 Area (km2)
 IUCN Category
 
Sampunong-Bolo Bird Sanctuary
 3
 I
 
Bulabog-Putian
 30
 III
 
Central Cebu
 200
 VI
 
Mt. Canlaon
 320
 II
 
Sudlon
 30
 VI
 
Olango Island Complex
 50
 I
 
Guadalupe Mabugnao-Mainit Hot Spring
 20
 PRO
 
Total
 653
  

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

 Types and Severity of Threats

Habitat destruction is the main threat to biodiversity in the Philippines, and Greater Negros-Panay is no different. Logging and shifting cultivation (kaingin) are cited as the primary forces of habitat conversion. Logging takes many forms, from industrial-scale to smaller-scale operations that use water buffalo to haul logs out of the forest. Mangroves are used locally for firewood, dyes, and tannins (Davis et al. 1995).

Hunting and the wild pet trade are also significant threats in Greater Negros-Panay. Leopard cats have been hunted for their pelts, and kittens are sold as pets (Heaney and Regalado 1998).

 

 Justification of Ecoregion Delineation

MacKinnon (1997) identified seven subunits in the Philippines, and the Philippine Biodiversity Action Plan (Philippine BAP 1997) demarcated fifteen biogeographic units. Udvardy (1975) identified the Philippines as a single biogeographic province. We delineated nine ecoregions in the Philippine islands, including Palawan. We deviated from Udvardy (1975), MacKinnon (1997), Stattersfield et al. (1998), and the Philippine BAP (1997) in varying degrees and based our delineation of the Philippine ecoregions on Heaney (1993), except that Heaney placed Sibuya, Tablas, and Romblon in a separate region.

We placed the islands of Negros, Panay, Tablas, Sibuyan, Masbate, Ticao, Siquijor, and Cebu into the Greater Negros-Panay Rain Forests [IM0114] ecoregion. MacKinnon also grouped these islands into a single subunit (26b). However, he also included the island of Bohol in this subunit. We followed Heaney (1993) and included Bohol as part of the Mindanao-Eastern Visayas Rain Forests [IM0129] because during the Pleistocene ice ages it was connected to Leyte Island. 

 References

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


Prepared by: John Morrison
Reviewed by:

 

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