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Habitat and Biodiversity
Climate is largely responsible for shaping the four widespread and several restricted types of habitats that originally occurred in the Philippines. Scroll down to learn about the different types of habitat, or jump to specific habitats using the links on the right. |
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Lowland Rain-Forest:
Originally the most common type of habitat, tropical lowland rain forest best fits the popular image of rain forest. The largest trees— two to three meters in diameter, not counting the massive supporting buttresses—reach 30 to 40 meters into the canopy, and a few stretch to 60 meters in height. Many of these trees belong to a single family, the dipterocarps, known for the beautifully lustrous wood marketed as "Philippine mahogany." Lianas and other vines reach from the ground to the canopy, providing a natural highway on which monkeys, squirrels, civet-cats, and lizards move from the dark quiet of the forest floor to the sunlight far above. Huge strangler fig trees wrap their tendrils around the branches and trunks of other trees, gradually overwhelming and killing their hosts, but the fig fruit they produce provides much of the food for raucous parrots, giant fruit bats, monkeys, and dozens of insect species. High in the canopy, delicate orchids and ferns grow in profusion, creating small pockets of soil dozens of meters above ground where tiny communities of earthworms, springtails, geckoes, and other species thrive. Surprisingly, the soil on the forest floor is often very thin and rocky because the high temperatures and wet conditions allow for extremely rapid decomposition of leaves and wood. Temperatures in lowland rain-forest almost always remain high, and a breath of wind is as rare on the forest floor as it is ubiquitous in the canopy above. Humidity within the forest rarely drops below 90 percent, even when weeks pass between rainstorms. In a few parts of the Philippines, the dry season lasts long enough that some trees drop their leaves for several months, but in most places the forest remains green and vibrant throughout the year.
Click Here for Photographic Examples of Lowland Forest |
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Montane Rain-Forest:
Beginning at about 1,000 meters elevation on most mountains, but starting as high as 1,700 meters on the highest and largest mountains, the lowland forest grades into montane forest. Montane rain-forest is shorter, reaching only to about 15 to 20 meters, with a maximum of 25 meters, and the trees rarely have the buttresses that are so conspicuous at lower elevation. Trees in the oak and laurel families dominate; vines are even more abundant, including an odd viney member of the palm group called pandans (Freycinetia) that is often festooned over the large trees. Pitcher plants and orchids are increasingly abundant in the trees; on the ground, moss covers roots and tree trunks, and leaf-litter covers rich organic soil. Rainfall here is high—two to three times that at sea level—and falls through most of the year, leaving the forest dripping with water. Sunbirds, resplendent with metallic greens, blues, and reds, flit through the trees seeking nectar from flowers, and, on the southern islands, giant flying squirrels chatter noisily in the night.
Click Here for Photographic Examples of Montane Forest
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Mossy Rain-Forest:
Still higher in the mountains, montane forest gradually gives way to mossy forest (sometimes called upper montane forest), in many ways the most dramatic and mysterious forest in the Philippines. Rainfall here may be the highest in the world—our site near the top of Mount Isarog, in southern Luzon near Naga City, gets up to 12 meters of rain per year; this is almost ten times the amount that falls in Portland, Oregon, famous for its damp climate, and five times more than the rainfall in Naga City near sea level. During most of the year, clouds flow into the forest at the tops of the mountains, saturating the long strands of moss that hang from the trees and causing up to several centimeters of drip-fall on nights when, technically, no rain has fallen. Because temperatures here are quite cool (averaging just 18° C for daily high temperature) and rainfall is so amazingly high, plants grow in thick profusion. High winds and steep terrain also work to keep trees small (only two to six meters), and nearly all trees are twisted and gnarled, looking much like a fairytail elfin forest. It is a miniature world of deep jade green, where a startling array of orchids, ferns, and mosses can grow on a single rotting log. Leaves, roots, moss, and branches decay more slowly than they are produced in a mossy forest, so that huge, springy mats of partially decayed vegetation, held together by live roots, can build to four or five meters deep. Open spaces within the mats provide a matrix of soil, caverns, and tunnel-ways for dense populations of earthworms, rodents, and poorly known frogs. It is this habitat that has, proportionately, the highest numbers of unique species; on Mount Kitanglad, in nothern Mindanao, a recent survey found that all twelve of the small mammals present, including two previously unknown species, were unique to the Philippines. All 16 of the bird species native only to Mindanao were abundant as well, including such remarkable species as the Apo mynah, the Apo sunbird, and the parrot-finch. Perhaps most startlingly, all ten of the species of earthworms found there were previously unknown to biologists.
Click Here for Photographic Examples of Mossy Forest
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Pine Forest:
In a few parts of the country that lie moderately far from the sea and within the rain-shadow of other mountains, another type of forest flourishes at 900 to 1,500 meters elevation—pine forest. This habitat is dominated by two species of pines also found to the north and west in Asia (Pinus insularis and P. merkusii). The longer-than-average dry seasons in these parts of the country promote fairly frequent fires that kill other trees but are tolerated by the pines; the resulting habitat is a parkland with pine trees widely separated by grassy areas. Heavy rains fall during parts of the year, and fog can be common. These regions are home not only to the world-famous rice terraces of the Ifugao and Bontoc people, but also to several birds familiar to northerners—crossbills and bullfinches—and to an exceptionally odd but beautiful rodent the size of a large house-cat, with long, flowing, silky black hair, known as the Luzon bushy-tailed cloud rat.
Click Here for Photographic Examples of Pine Forest
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Other Habitat:
Three additional types of habitat deserve mention, even though they originally occupied only a small portion of the country (and even less today). Mangrove forest could be found in coastal areas where seawater and freshwater mixed in bays and at the mouths of rivers. Due to the influx of organic material carried by the rivers, biological productivity in such places is very high. Mangrove forest is a crucial breeding habitat for many species of marine fish and shore-birds.
In places where limestone outcrops cover extensive areas, natural erosion has given rise to a beautiful landscape referred to as "karst," dominated by white cliffs and ridges riddled with small caves. Rainwater quickly drains away into the caves, leaving behind parched conditions where only a few species of trees can prosper. The forest here, usually called limestone forest, is dominated by the molave tree (Vitex parviflora), which tends to grow in the few pockets of deep soil, with clumps of bamboo and small leguminous trees occupying much of the remaining land. The diversity of plants here is low, but but those that are present tend to be highly restricted, unique species that provide habitat for a unique set of butterflies and other insects.
The final type of forest forms where unusual rocks, called ultrabasic or serpentines, predominate. The soils that form from these rocks are extremely unproductive because they are very high in iron and magnesium and very low in most other nutrients, allowing only specialized species of plants to survive. The ultrabasic forest thus supports only a few species, although many of those are restricted to the Philippines. It is often low in stature, giving rise in some places to a shrubby, heath-like vegetation.
Each of these forest habitats contributes to the grand structure of the natural environment of the Philippines, and pssesses individual climatic features that enable a unique set of plants and animals to survive. All of the habitats may be present in form or another on all of the Ice-Age islands described above. Diversity in the Philippines is therefore determined not just geographically, but also climatically within each island. It is the combination of geological and climatic variation that has led to the profusion of life in the Philippines, a profusion not of large numbers of species residing in a single vast habitat, as in the Amazon basin, but of sets of species unique to a great number of small areas of habitat. The diversity of life indigenous to the Philippines is a story of unique places, each with its own tale to tell.
Click Here for Photographic Examples of Other Habitat
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To begin the next chapter, "Vanishing Treasures," click the forward arrow below. |
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