The Philippines, a country of more than 7,000 islands with a combined landmass of 300,780 square kilometers, is the second-smallest of the 17 megadiversity countries in the world. It is also one of the most threatened hotspots, due to its population density - the highest in Southeast Asia except for Singapore. The islands, most of which are now inhabited by humans, feature diverse topographic landscapes ranging from rugged volcanic mountains, plateaus, and vast fertile plains - now cropland for rice, corn, and coconut - to long coastlines with some of the world's most colorful coral reefs.
The varied geological histories of the different parts of the archipelago, with diverse climates and topography, contribute to the exceptionally diverse biota in the country. Each biogeographically distinct set of islands is home to a unique community of species of plants and animals, with larger islands holding more unique species than most countries, and even small islands supporting greater biodiversity than the biologically richest countries in Europe. The diversity of small biogeographic regions in such a compact area makes the Philippines ecologically unique.
The Philippines is probably the most biologically diverse country in the world, in terms of unique terrestrial and marine plant and animal species per unit area. Moreover, the country has more endemic species than some larger megadiversity centers. Plant endemism is reported to be between 45-60%. The 2000 IUCN Red List of Threatened Species includes 193 species considered Threatened (Critically Endangered, Endangered and Vulnerable) in the Philippines.Invertebrate diversity is also high in the Philippines, with butterflies alone accounting for 895 species, 39% of which are endemic - the second-highest number of endemics in the world after Indonesia.
There are five major centers of endemism in the country and at least five minor ones, each supporting its own unique set of mammals, amphibians, plants, birds, reptiles, and butterflies, and each geographically isolated from the others.
The Sierra Madre Corridor is mostly terrestrial, but includes some of the Batanes-Babuyan islands straddling the South China Sea and the Northern Pacific zones. The terrestrial side is within the Greater Luzon Biogeographic Region and is largely defined by the Sierra Madre mountain range, the "backbone of Luzon" and the longest mountain range in the country. The corridor has a land area of about 1.8 million hectares in 10 provinces (Batanes, Cagayan, Isabela, Nueva Vizcaya, Quirino, Nueva Ecija, Aurora, Bulacan, Rizal, and Quezon) in Administrative Regions 2, 3 and 4.
Sierra Madre contains the greatest number of protected areas - 68 national parks, watershed forest reserves, natural monuments, marine reserves, protected landscapes and seascapes in all. Of these, the Northern Sierra Madre Natural Park is the largest and most important because it was the precursor to the biodiversity corridor concept and has served as a model for other regions in the Philippines. The corridor is not only rich in species diversity and endemism, but is home to many indigenous peoples, including the Agtas/Dumagats, Isneg, Ibanags, Ikalahans, Gaddangs, Ifugao, Ilonggots, and the Bugkalots or Negritos.
The forest cover in the Sierra Madre Corridor is the most extensive in the Philippines - about 1.4 million hectares, accounting for 25% of the country's forest resources, including more than 40% of the remaining old growth forests. Of the 13 forest types in the Philippines recognized by Whitmore (1984a), 11 were reported present in the corridor, including tropical evergreen rainforest, upper and lower montane rainforests, limestone forest, forest on ultramafic substrate, beach forest, and wetlands such as mangrove forest and freshwater swamp.
The biological importance of the corridor is not only due to the remaining intact forest in the central part of the mountain range, but also to the high plant biodiversity, with more than 3,500 species recorded in the area. This represents about 45% of species recorded in the country. The highest number of endemic plant species is found in this corridor, with 58% endemism within the corridor and 41% relative to the national figure. Generic endemism is also high, with 68% of endemic genera found in the corridor. The number of threatened plant species in the IUCN Red List is 106 for the corridor - or 42% of the total threatened species of Philippine flora.
The Sierra Madre corridor has the highest species diversity of birds in Luzon, accounting for at least 80% of all resident breeding birds of Luzon. Fourteen (20%) of the country's 65 threatened bird species have been recorded in Luzon. Diversity of other taxa is only partially documented, but species diversity generally is high, including 38 mammals, 40 reptiles and 17 amphibians. Five mammals and six reptiles are threatened with extinction. A total of 25 threatened higher vertebrates are present in the corridor, 75% of them endemic to the Philippines.
The corridor has 12 endemic amphibians (71%). Of the endemic bird species recorded in Luzon, 83% are present in the corridor - 84 species. At least 55% of the mammal species in the corridor are endemic (21 species, or 24% of all endemic mammals found in Luzon). At least 16 reptile species (40%) are endemic.
Palawan is geologically part of the Sunda Shelf (which includes Borneo, Sumatra, the Malay Peninsula, and Java), and is a biogeographic region of its own. Palawan is the fifth-largest island in the Philippine archipelago with an area of more than 11,000 square kilometers. It has a long mountainous backbone with three peaks above 1,500 meters.
Several land formations in Palawan are of botanical importance: the Balabac islands; the ultrabasic formations in the mountain peaks of Mt. Mantalinghangan, Victoria/Anapahan, and Mt. Bloomfield; primary forest of Mt. Puyos (Cleopatra's Needle); karst formation of the rugged limestone terrain in the northern and northwest portion of the mainland (including El Nido); and the Calamianes group.
The biological importance of Palawan is recognized both nationally and internationally. In 1990, UNESCO declared the entire area as a Biosphere Reserve. The region includes several existing Proclaimed Conservation Areas - namely, Coron Islands (7,580 hectares), El Nido Marine Reserve (89,140 hectares), Malampaya Sound (90,000 hectares), and St. Paul's Subterranean River National Park. The entire province has also been declared a mangrove reserve.
Palawan encompasses various types of forest formations ranging from mangrove and beach forests to forests on ultramafic and limestone rocks, tropical lowland evergreen, moist deciduous, and upper montane rain forests. The northern part of the island is home to the endemic plant genus
Adonidia (Palmae). It has been estimated that the island contains about 1,522 species of flowering plants with 15-20% endemism.
Palawan supports 11 amphibians (46%) endemic to the Philippines - eight of which are found only in Palawan. The island is also home to 25 Philippine endemic birds (15%), including 16 (62%) that occur only in Palawan, 18 endemic mammals (33%), including 15 (83%) that are endemic to Palawan, and 24 endemic reptiles (36%).
In terms of conservation status, 23 faunal species are threatened: nine birds, six mammals, five reptiles, and one amphibian. At least 14 of the threatened species (61%) are endemic.
Eastern Mindanao forms part of the Greater Mindanao Biogeographic Region. Its northern boundary is Siargao Island, and it extends south to where Mt. Hamiguitan rises. To the west, portions of the Agusan Marsh delineate the area.
Agusan Marsh has been declared a Wildlife Sanctuary and one of the 10 priority protected areas in the Integrated Protected Areas System; meanwhile, Siargao Island, Bucas Grande, and other smaller adjacent islands and islets were declared as a unit having a Protected Landscape and Seascape status. Thirty-four sites have been prioritized by the National Conservation Priority-setting Workshop process for conservation within this region. Of these, 15 are classified as
extremely high priority - critical, 5
extremely high priority -
urgent, and 11
extremely high priority.
One of the largest remaining blocks of dipterocarp forest in the country is found along the eastern portion of Mindanao. In fact, 75% of the country's extracted timber comes from this area. Plant diversity in the corridor comprises more than 2,300 plant species, accounting for some 31% of the Philippines' total. Of these, 60% are endemic to the corridor and account for 29% of Philippines' endemics. Eight endemic genera, 26% of the country's total, are found in this region. Thirty-one floral species in the corridor are threatened.
Bird diversity comprises about 178 species (67%) of resident breeding birds and mammal species (37) represent 42% of the native mammals in the Mindanao Biogeographic Region. Diversity of other taxonomic groups is only partially documented, but species diversity is high, including 26 amphibians and 62 reptiles.
Eastern Mindanao has 16 amphibian species endemic to the Philippines (42%), several of which are confined to Mindanao. The corridor is home to 85 bird species, 81% of all Philippine endemics recorded in the Mindanao Biogeographic Region. It has 25 endemic mammal species (57%), including two species found only on Dinagat Island. Finally, Eastern Mindanao has 36 endemic reptiles (53%), several of which are confined to Mindanao.
In terms of conservation status, at least 22 species are threatened, including the Philippine Eagle, Philippine Cockatoo, the Golden-crowned flying fox, and the Philippine crocodile. Siargao Island is home to the second-largest mangrove forest in Mindanao (86 square kilometers) and the largest contiguous stand of mangroves in the country (40 square kilometers).
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