The Beauty of the Philippines: Its Biodiversity

Blogger's Note: An article by the former DENR Secretary showing the richness of species diversity of our country.

The Philippines & its rich biodiversity
by Angel C. Alcala, Siliman University, 15 May 2005. Manila Bulletin

THE term biodiversity, coined by Walter Rozen of the United States Academy of Science in 1986, was first used by E.O. Wilson, the famous Harvard biologist, in 1988. Since that time, it has become increasingly popular among biologists, and is now entrenched in the scientific literature. The term encompasses the total richness and variety of life on earth. Biodiversity studies are directed at five levels of biological organization: Gene, species, population, community, and ecosystem. This paper will focus on Philippine biodiversity at the species level.

The Philippines, with a land area of 300,000 square kilometers, is one of the countries in the world with a very rich diversity of species. It has an estimated 13,500 species of terrestrial plants, 8,000 of which belong to the flowering group. About 40 percent of these flowering plants are endemic. Of economic and scientific interest are 39 species of trees in the Family Dipterocarpaceae, the source of Philippine mahogany.

Its biodiversity in vertebrate animals compares favorably with that of Brazil and Madagascar, two countries known for their outstanding biodiversity — Brazil, which is 28 times larger than the Philippines, and Madagascar, which is two times larger than the archipelago. The country is home to about 911 species of resident and breeding terrestrial vertebrate animals. These compose approximately 100 amphibians (80 percent endemic), 240 reptiles (70 percent endemic), 396 birds (44 percent endemic), and 175 mammals (64 percent endemic). We have about 529 endemic species as compared to Brazil’s 725 endemic species, considering that Brazil is 28 times larger than the Philippines. Madagascar, which is twice larger than the Philippines, has only 90 unique mammals vis-à-vis our 111 unique mammals.

While the country possesses no extensive freshwater habitats, Lake Lanao was reported to harbor about a dozen endemic species in three or four genera of true freshwater fish of the Family Cyprinidae. The species richness of corals, shells and fish is very high in the fertile triangle formed by the Philippines, New Guinea and the Malay Archipelago. Some 400-500 species in 90 genera of hermatypic (reef-forming) corals and 4,000 species of marine fishes are believed to have existed in this area. The 900,000-square-kilometer Sulu-Sulawesi Sea (part of this fertile triangle) is home to 2,500 species of fish including a species of coelacanth, five species of marine turtles, and 22 species of marine mammals. However, small reef systems harbor much fewer fish species. For example, 200 species have been observed on two reefs in the Central Visayas over a period of 30 years. Pristine reefs in the country such as Tubbataha Marine Park should have more than this number.

For the Philippines, the factors that are responsible for the high species richness in old-growth tropical rainforests are: (1) geologic age (main land masses more than 50 million years old), (2) tropical location providing equable climatic conditions, (3) environmental heterogeneity as shown by diversification and complexity of microhabitats, (4) insular (island) condition, and (5) contiguity to a large land mass (Asia) and islands in the south and southeast serving as source of immigrants. The first four factors have favored the development of new species (speciation) through evolutionary processes operating on biological and genetic materials of immigrants. Movements and distribution of terrestrial species are limited by natural barriers that influence speciation processes such as bodies of water, high mountain peaks, and in modern times by cultivated areas.

In contrast, oceans and seas tend to be connected to each other. Oceanographic processes, including water mass movements, ocean currents, etc., provide the mechanisms to transport marine propagules and to connect distantly located marine areas. For example, the Pacific Ocean connects to the Sulu Sea through ocean currents in the Bohol (Mindanao) Sea moving southwestward, and the South China Sea connects to the Sulu Sea through the Mindoro and Balabac Straits. Because of this connectivity, mixing of genes in the population of marine species occurs, and endemism is lower in marine organisms than in terrestrial ones. This is illustrated by the similarity and the low endemism of corals and reef fishes of the Philippines. Because of the wide distribution of marine propagules over large areas of oceans, the incidence of species extinction among marine species is also low. The differences between terrestrial and marine environments imply that approaches to biodiversity conservation would also differ between terrestrial and marine species.

As widely known, Philippine biodiversity has been affected not only by natural events but also by human-induced factors especially during the past 50-60 years. The effects of man’s activities on Philippine biodiversity may be assessed in a general way in terms of two measures, species richness and abundance using groups of terrestrial organisms (rainforest trees and land vertebrates), and marine organisms (corals and reef fishes), for which there are some data.

The Family Dipterocarpaceae, comprising 39 species in the Philippines, is now represented by only 14 species in several limestone forest fragments with a total area of ca 300 hectares in southwestern Negros Island. The number of species that may have gone extinct during the past years is not known. However, there is little doubt that the abundance of this tree family has been reduced because of forest degradation. The various vertebrate groups in these forest fragments have shown variable responses to human impacts. The amphibians and reptiles have lost more than 20 percent of the species occurring there 50 years ago. The birds appear to have lost a few endemic species. The mammals, especially the volant species’ (fruit bats), have not lost any species during the past 50 years, but a couple of species have become rarer and are on the verge of extinction. The population of large herbivores has also been reduced.

The degradation of Philippine coral reefs has been sufficiently documented. Only about 5 percent of coral reef sites explored have at least 75 percent live coral cover, and 70 percent of the surveyed sites have only 25 percent cover or less. Majority of coral reefs have much reduced numbers of carnivorous fishes (fish eaters or top carnivores) and some have virtually none of these fishes anymore. However, no coral or top carnivores have been shown to be extinct. Density of reef fishes in general is low (< 200/500 square meters) on heavily exploited reefs. Target (or food) fish biomass on such reefs is usually less than 10 kilograms per 1,000 square meters, in contrast to more than 100 kilograms per 1,000 square meters in more pristine or protected reefs.

The loss or decline of species richness and abundance of terrestrial and marine species in the Philippines has serious negative effects on the social and economic well-being of our people. Hence, efforts to protect what remain of our biodiversity are urgently needed.