BIODIVERSITY
It is generally accepted that the Philippine Islands contain some of the highest levels of terrestrial and marine biodiversity on the planet. Much of there amazing biodiversity comes from several synergistic factors such as geological history, variety of habitats and geography.
To understand Philippine biodiversity, we need a bit of history about the origins of biodiversity within the entire Indonesia-Pacific region (Indo-Pacific). Probably one of the most important geological events that lead to increased diversity was the Pleistocene glacial period, which lasted until from about 1.5 million yeas BP (Before Present) to about 10,000 years BP. During the ‘ice age', much of the world's ocean was locked up in the northern and southern latitudes, thus exposing much of the land around Southeast Asia and Indonesia (called the Sunda Shelf). Islands in the region were now connected via land bridges and the once nearly continuous sea was fragmented in many areas. This had a major affect on the marine and terrestrial animal distributions and diversity. On land, animals that were restricted to islands or to the mainland, primarily due to their inability to cross the sea, were now able to move freely about the larger area and even access other islands via land-bridges. In the marine environment, the once nearly continuous bodies of water were now ‘isolated' or separated from each other due to the increase exposure of land and land-bridges. For hundreds of thousands of years, animals in the sea and on land continued to evolve. Terrestrially, many animals adapted to their new regions. In the ocean, many fish and invertebrates evolved within the isolated marine environments.
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| No island archipelago was more affected than the Philippines. Thousands of islands in the archipelago were now joined together or close enough that the physical barrier of the sea presented little challenge for the migration of bird and mammal species. Palawan benefitted like few other islands in the Philippines. Its probable land-bridge with Borneo allowed for dozens of species of mammals and birds to migrate over from Borneo. The deep sea still in existence between Palawan and the rest of the Philippine islands, however, prevented many of these animals from continuing on. This has been suggested as the reason why Palawan shares many of the same mammals and birds as Borneo, unlike any other island in the archipelago. |
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The relatively isolated seas around the Philippines; the South China Sea, Sulu Sea, Celebes Sea, Philippine Sea, and Pacific Ocean all contained numerous distinct marine species by the end of the Pleistocene.
When global temperatures started to rise, the glaciers melted and within a relatively short period of time flooded the Sunda Shelf, re-forming thousands of islands and re-joining several bodies of water. This event stranded and isolated many animals on land, leading to many of the distributions we currently see today. Many of these animals evolved into distinctive species within their habitats. In the ocean, organisms that evolved in relative isolation were now mixed with thousands of other species from other parts of the Indo-Pacific Region. It was the diversity of habitats, however, that played an important role in maintaining the high diversity we see today…
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The number of habitats in the Philippines is staggering. Between the tallest mountains to the deep Philippine trench are subalpine, montane, and lowland forests growing on a variety of substrates such as limestone and basalt. Mangroves, shallow marine bays, isolated and deep lagoons, fringing, plateau and barrier reefs and the list goes on. All of these habitats provide niches for organisms and was never more important than when the sea level rose and either mixed marine species together or isolated dozens of terrestrial animals on smaller areas of land. Since no two species can occupy the same niche, it was the un-imaginable number of niches within the habitats that allowed for so many species to coexist in the same area. Habitat, however, is often a function of location… |
The entire Philippine archipelago is located in the Tropical Zone, an area with stable temperatures, periods of torrential rainfall and high levels of sunlight. To explain how these conditions result in high biodiversity is a several page explanation in itself, but essentially these factors lead towards increased levels of symbiosis (two different species living together, yet using different resources on which to survive) and forcing organisms to ‘re-define' or partition niches into smaller ‘units'. As more species made or filled a particular niche, more niches ultimately were ‘opened' for even more species to fill. In other words, biodiversity leads to higher levels of biodiversity.
Geographically, the Philippines are situated between several bodies of water including the Philippine Sea, Celebes Sea, South China Sea, Sulu Sea, and Pacific Ocean. Since almost all marine bony fishes and invertebrates have a planktonic, or free-swimming, stage in their life cycles as the bodies of water circulate, the potential to bring larva of coral, fish, and invertebrates to the Philippines from different parts of the Indo-Pacific region is very high.
Finally, it has recently been recognized that one area in particular has the highest marine biodiversity on the planet. This area is called ‘The Coral Triangle' of which the Philippine Islands make up the entire northern border. Within this triangle, only western Papua New Guinea is reported to contain more marine species than the Philippines…but just barely. It is argued even to this day that the Philippines, particularly around Mindoro and northern Palawan Islands, are the center of the center of marine fish biodiversity. For scholars, it is a question of species per area rather than species per region. But for us, the joy and awe at gazing at over 1600 species of fish, over 600 species of invertebrates, and over 500 species of coral makes the details academic! |
