archaeological, linguistic, or human biological evidence.
However, it is certain that later Polynesian voyaging canoes
had the technical capability to reach the Americas, and
to return. That the Polynesians did indeed reach South
America and return is strongly suggested by preserved
remains of the sweet potato (Ipomoea batatas), a South
American domesticate, recovered from several prehistoric
Polynesian sites (such as the Tangatatau rockshelter on
Mangaia, Cook Islands). Further evidence of contact has
recently been provided by the bones of chickens (Gallus gallus, a Polynesian domesticate) from a pre-Columbian archeological site in Chile. More controversial has
been the claim that Polynesians may have introduced the
technology of plank-built canoes to the Chumash of the
Channel Islands, off the coast of California.
SEE ALSO THE FOLLOWING ARTICLES
Archaeology / Cook Islands / Easter Island / Exploration and
Discovery / Human Impacts, Pre-European / Kon-Tiki /
Polynesian Voyaging / Tonga
FURTHER READING
Bellwood, P. 1985. Prehistory of the Indo-Malaysian archipelago, revised ed.
Honolulu: University of Hawaii Press.
Irwin, G. 1992. The prehistoric exploration and colonisation of the Pacific.
Cambridge: Cambridge University Press.
Kirch, P. V. 2000. On the road of the winds: an archaeological history of
the Pacific Islands before European contact. Berkeley: University of
California Press.
Kirch, P. V., and R. C. Green. 2001. Hawaiki, Ancestral Polynesia: an essay
in historical anthropology. Cambridge: Cambridge University Press.
Lilley, I., ed. 2006. Archaeology of Oceania: Australia and the Pacific Islands.
Oxford: Blackwell Publishing.
Spriggs, M. 1997. The island Melanesians. Oxford: Blackwell Publishing.
PHILIPPINES, BIOLOGY
RAFE M. BROWN
University of Kansas, Lawrence
ARVIN C. DIESMOS
National Museum of the Philippines, Manila
The Philippines (Fig. 1) is one of the Earth’s most spectacular island archipelagoes. The country spans the Asian–
Australian faunal zone interface at the sharpest biotic
demarcation (Wallace’s Line) on the planet. Although
collectively comprising a land mass approximately the
size of the U.S. state of Arizona, the Philippines is a complex archipelago with more than 7100 distinct islands.
Geographically situated on the edge of multiple colliding tectonic plates, the Philippines has an ancient and
complex geological history that has only recently come to
light. Ancient land mass movements, environmental gradients along steep volcanic slopes, and sea level–induced
alterations of connectivity between neighboring islands
have all presumably fueled the in situ evolutionary process of diversification on a magnitude seen in few other
island systems. The result is a spectacular array of biodiversity, unparalleled levels of vertebrate endemism, and
some of the planet’s most spectacular examples of life on
islands. The Philippines is a global superpower of biodiversity that may possess one of the highest concentrations
of vertebrate life on Earth.
FIGURE 1 The position of the
Philippines (darkly shaded islands) in relation to surrounding
Southeast
Asian
and
Australasian land masses. The
positions of Wallace’s and
Huxley’s lines are indicated
for reference. Wallace’s line
marks the edge of the Sunda
Shelf
and
the
transition
between Asian and Australian
faunal regions. Huxley’s line
separates Palawan and associated land bridge islands
from the truly oceanic portions of the Philippines.
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FIGURE 2 Species exemplars from the extraordinarily diverse endemic
Philippine rodent radiation: (A) Luzon hairy-tailed rat, Batomys granti;
(B) Cordillera striped earth-mouse, Chrotomys whiteheadi; (C) Luzon
needle-nosed shrew-rat, Rynchomys cf soricoides; (D) Kalinga shrewmouse, Archboldomys kalinga; (E) silver earth-mouse, Crotomys
silaceus; and (F) common Philippine forest rat, Rattus everetti. Photographs by Rafe M. Brown.
GEOGRAPHICAL AND GEOLOGICAL SETTING
The Philippines is situated south of Taiwan and north
of Borneo and Sulawesi (between the equator and the
Tropic of Cancer), separated from the Asian mainland by
the South China Sea. Collectively the archipelago covers
2 million km2 with a total land mass of approximately
300,000 km2.
The western part of the archipelago (Palawan, Balabac,
Busuanga, Coron, and smaller associated islands) has had
a stable geologic configuration and has been intermittently
connected (or nearly connected) to northern Borneo via
a narrow land bridge during maximum exposure of the
world’s largest continental shelf (the Sunda Shelf ). The
remaining portions of the Philippines are classified as oceanic islands and are believed to have risen directly from
the ocean floor as a result of volcanic activity associated
with subduction of the Philippine Plate at the western
boundary of the Pacific Ring of Fire.
BIODIVERSITY AND ENDEMISM
The Philippines is recognized internationally as a global
stronghold of biodiversity. The shallow, warm seas sur724
Gillespie08_P.indd 724
rounding the country support the richest coral reef communities on the planet and are literally the epicenter of
Southeast Asian and southwestern Pacific marine diversity. Terrestrial ecosystems in the Philippines are similarly
diverse, supporting a wealth of natural resources, habitat
heterogeneity, and a rich array of species diversity. High
levels of alpha-diversity (species richness) and beta-diversity (variation among adjacent regions) place the Philippines among the world’s most biodiversity-rich countries.
Some of this diversity is truly astonishing. Highlights
include dwarf water buffalos or “Tamaraw” (Bubalus
mindorensis), the largest extant forest eagle in the world
(Pithecophaga jefferyi), a radiation of the world’s largest
flowers (genus Rafflesia), the rarest batagurid turtle in the
world (Siebenrockiella leytensis), an extensive and exceptionally diverse rodent radiation (including such novelties
as raccoon-sized “cloud rats” and needle-nosed shrew-rats
that feed entirely on worms; Fig. 2), four endemic genera of snakes, five endemic species of spectacularly maned
wild pigs, and such “living fossils” as the primitive and
relictual flat-headed frog (Barbourula busuangenis). The
fossil record shows that many extraordinary, large-bodied animals have gone extinct with the arrival of modern
humans, including dwarf buffalos, elephants, and giant
land tortoises.
Terrestrial ecosystems are fantastically diverse. Recent
summaries of birds recognized 593 species (32% endemic);
mammal diversity currently is estimated at 175 native terrestrial mammals (65% endemic). Recent reviews of the
classification of Philippine amphibians and reptiles recognized 105 species of amphibians (79% endemic) and
264 reptiles (68% endemic). These estimates emphasize
conspicuous terrestrial vertebrates, but total country estimates (Table 1) are awe inspiring, with as many as 15,000
plants (and their relatives) and 38,000+ animals (vertebrates and invertebrates), for a startling total of 53,500
species. These numbers should be viewed as conservative
approximations; numerous recent studies have shown
that terrestrial biodiversity of the Philippines is substantially underestimated, in some cases grossly so. In poorly
studied groups such as earthworms, more than a hundred
TABLE 1
A Summary of Recent Estimates of Total Countrywide Philippine
Species Diversity
Taxonomic Group
Philippine Total
Vertebrates
Invertebrates
Plants
Others (algae, lichens, fungi, etc.)
Total
3,308–3,325
34,940–35,000
14,000–15,310
6,100+
53,500+
PHILIPPINES, BIOLOGY
4/22/09 3:33:49 PM
FIGURE 3 Estimated Cenozoic movements of Philippine land masses
(modified from work of Hall 1998) 10, 20, and 30 million years ago.
new species have recently been discovered. Molecular
phylogenetic studies have confirmed the exceptional species diversity of numerous Philippine radiations; many
have uncovered suites of previously unrecognized, cryptic
species. Several of these key studies of species boundaries have produced startling results and increased species
diversity in selected groups by 30–50%. Virtually every
molecular phylogenetic study that has been published in
the last 10 years has included the discovery of new hidden
species, including many groups of frogs, lizards, insects,
worms, forest mice, bats, rats, and birds.
One example is the case of the Philippine forest frogs
of the genus Platymantis. Past studies were based solely
on morphology; species numbers grew slowly from 7 to
12 named species between 1950 and 1990. It was at this
point that a group of herpetologists began to focus on
bioacoustic characters (analysis of the mating calls of male
frogs) and applied molecular techniques (DNA sequence
data) to the problem of species boundaries in this group.
By emphasizing different aspects of the phenotype, these
workers provided fine-scale taxonomic partitioning of
FIGURE 4 Spectacular Philippine endemic species: (A) the endemic
Philippine freshwater crocodile, Crocodylus mindorensis (photograph
by Rafe M. Brown); (B) the newly discovered Calayan Island flightless rail, Gallirallus calayanensis (photograph by Marge Babon/CEAE);
(C) the giant flower Rafflesia manillana (photograph by Arvin Diesmos); (D) and one of the world’s only fruit-eating monitor lizards, Varanus olivaceus (photograph by Charles Linkem).
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forest frogs and opened the way for a flood of discoveries
and new species descriptions. It is clear that Platymantis, currently estimated at 27 described species, represents
one of the Earth’s major island radiations of frogs. Several
dozen species remain to be described. When the same analytical tools are applied to other frog groups throughout
the archipelago, it becomes clear that the species diversity
of Philippine Amphibia has been underestimated by as
much as 30–40%.
Despite the lack of a complete knowledge of the biodiversity of the Philippines, today’s taxonomic estimates allow
researchers to calculate the number of species per unit area.
When this calculation is carried out for terrestrial species,
given the available land mass (300,000 km2), the end result
is the highest concentration of biodiversity on Earth.
BIOGEOGRAPHY AND PROCESSES
OF DIVERSIFICATION
FIGURE 5 Spectacular Philippine endemic species: (A) the recently
discovered Mindoro stripe-faced flying fox, Styloctenium mindorensis
(photograph by Jake Esselstyn); (B) the rarest batagurid turtle in the
world, the Philippine forest turtle, Siebenrockiella leytensis (photograph
by Rafe M. Brown); (C) the endemic Philippine dwarf water buffalo or
Tamaraw, Bubalus mindorensis (photograph courtesy of Department
of the Environment and Natural Resources–Protected Areas and Wildlife Bureau Tamaraw Conservation Program); (D) the brightly colored
Igorot frog, Rana igorota (photograph by Rafe M. Brown).
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Several generations of biologists have converged on a
startling consensus: The extraordinary biodiversity of the
Philippines has likely been produced by three major processes of the geographic template (i.e., geology + climate).
We consider these process to be the major “generators” of
diversity in the Philippines. The first involves the complex
geological history of the archipelago. Briefly, the formation
of the Philippines involves more than 50 million years of
collisions of multiple separate plates of the earth’s crust,
resulting in a history characterized by constantly changing
configurations of islands. The Philippines of 10, 20, or 30
million years ago looked almost nothing like the country
today (Fig. 3). The inferred result of these ancient movements of land masses is that the distant ancestors of many
of today’s Philippine endemic species may have first invaded
and become isolated on Philippine paleo-islands several to
many tens of millions of years before present. These events
appear to have given rise to deep phylogenetic diversity and
the presence of numerous “old endemics,” or highly divergent, taxonomically distinctive taxa (Figs. 4 and 5).
The second generator of biodiversity in the Philippines is the process of evolutionary differentiation along
dramatic elevational, atmospheric, and environmental
gradients from sea level to 2000+ meters (Fig. 6). The
oceanic portions of the Philippines are islands produced
primarily by volcanism. Many of the smaller islands (and
many isolated peaks within larger islands) were formed as
active volcanoes arose from the ocean floor over the last
100 million years. Steep elevational gradients (replicated
PHILIPPINES, BIOLOGY
4/30/09 10:38:49 AM
numerous times along dozens of isolated volcanic peaks)
have given rise to atmospheric variation, microclimate
variability, and forest community heterogeneity—resulting in biodiversity gradients along these sheer mountain
slopes. As a result, the study of Philippine biodiversity is
largely the study of species succession along environmental gradients. The last 50 years of biodiversity research in
the Philippines have documented the enormous impact
that elevation-associated atmospheric and habitat gradients that have played a prominent role in the evolutionary
processes of diversification.
The third generator of Philippine biodiversity (and
the one that is, for better or for worse, most often
invoked) is the repeated “species pump” action of rising and falling sea levels between the mid- to late Pleistocene (350,000–12,000 years ago). Repeated cooling
episodes during this recent time period resulted in the
capture of the Earth’s water at the expanding polar ice
caps and a concomitant lowering of sea levels throughout the globe. In the Philippines the result of these sea
level oscillations was repeated episodes of connectivity
and isolation between islands separated by channels of
120–180 meters (Fig. 7). Biogeographers now recognize
at least eight faunal provinces that correspond to these
Pleistocene Aggregate Island Complexes (PAICs), which
represent maximum exposure of expanded islands. Each
PAIC is a major center of biodiversity and endemism,
with distinctive flora and fauna. The tracing of submarine bathymetric contours to reveal Pleistocene exposure
of land provides biologists with an estimate of former
paleoisland connection and serves as a basis for predictions of taxonomic affinity (in the absence of phylogenetic data) for the species inhabiting those islands. This
exercise has also identified several minor subcenters of
biological diversity in the form of small islands. Finally,
it is clear that both in situ evolutionary diversification
and repeated colonization events have contributed to the
accumulation of diversity in the archipelago.
The development of molecular phylogenetic methods
has allowed for unprecedented study of both biodiversity
in general and the historical and temporal framework for
FIGURE 6 Striking elevational gradients and volcanic landscapes of
the Philippines: (A) Pagudpud area, northern Luzon Island; (B) Lake
Danao, a high-elevation volcanic crater lake in northern Leyte Island;
(C) the saw-toothed peaks of Mt. Guiting-guiting, Sibuyan Island; and
(D) terraced fields along the slopes of the northern Cordillera Mountain
range (between Bontok and Banaue). Photographs by Rafe M. Brown.
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FPO
FIGURE 7 A detailed map of the Philippines (light green shaded islands) with Pleistocene Aggregate Island Complexes (PAICs) indicated by tracing
of 120 m underwater bathymetric contour. Areas shaded purple indicate shallow seas that may have been exposed as many as ten times during the
middle- to late Pleistocene. These land-positive connections (land bridges) may have allowed for past floral and faunal exchange between islands
that today are isolated by marine channels.
the generation of Philippine biodiversity. Several modern
phylogenetic studies have produced surprises that contradict earlier hypotheses and threaten to topple the prevailing view of diversification in the Philippines. The result is
an emerging consensus suggesting that Philippine biodiversity is far more complex than previously thought.
Recent studies of Philippine flying lizards, forest
geckos, spotted stream frogs, and forest mice suggest
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that for some taxa, periodic sea level oscillations have
had a profound impact on the production and distribution of species diversity. These studies have all demonstrated a near complete adherence of species to PAIC
boundaries and Pleistocene seashores. For much of the
terrestrial vertebrate life in the Philippines, these historical events have played a predominant role in shaping
species distributions—much more so, in fact, than the
PHILIPPINES, BIOLOGY
4/22/09 3:33:56 PM
traditional biogeographic variables such as island size
and distance from mainland. This dominant paradigm
of Philippine biogeography is so prevalent, in fact, that
the shared presence of species across PAIC boundaries is
now viewed as an extreme outlier. For the most part, this
has been a healthy development for the understanding
of Philippine biodiversity. By heightened attention to the
unique evolutionary histories of PAIC endemics, biogeographers are now beginning to arrive at an appreciation
of Philippine biodiversity that is concordant with evolutionary history—one that recognizes distinct and cohesive
lineage segments as evolutionary species. The end result is
that a truly evolutionary classification of Philippine vertebrate life is now perceived as an obtainable goal.
Several recent studies have dramatically upset accepted
scenarios concerning the predominant processes of evolutionary diversification in the Philippines. One study, a phylogenetic analysis of Asian “Fanged Frogs” conducted by
Ben Evans and colleagues, revealed a pervasive and entirely
unexpected zoogeographic link between Sulawesi and the
Philippines. In that study, DNA sequence data revealed
that multiple over-water dispersal events have allowed for
successive waves of exchange between Sulawesi and the
Philippines. As might be expected, the oldest invasions
gave rise to proportionately more species and have spread
across more PAICs than the younger arrivals. This Philippine–Sulawesi connection stands in opposition to all previous zoogeographic evidence provided by the last 25 years of
studies of Philippine vertebrates, particularly mammals.
Additional studies have upset the land-bridge (Palawan)
versus oceanic (remaining Philippines) dichotomy. Phylogenetic studies of fanged frogs, spiny rats, shrews, litter
frogs, spotted stream frogs, slender stream frogs, emerald
tree skinks, flying lizards, geckos, fresh water fish, river
shrimp, and numerous groups of insects all demonstrate
that a large portion of Palawan’s endemics are most closely
related to the truly oceanic portions of the Philippines, to
the exclusion of the (expected) species from the islands
of the Sunda Shelf. In fact, many Palawan endemics are
nested within the truly Philippine radiation, suggesting
recent dispersal to Palawan from the oceanic portions
of the Philippines, and a lack of faunal exchange with
Borneo. The simple depiction of Palawan as a faunal
extension of northern Borneo (based largely on mammal
and bird taxonomy) is a taxon-biased expectation that is
not supported by the bulk of available phylogenetic evidence. In fact, Palawan is an exceptional amalgamation of
greatly divergent ancient taxa, recent dispersal events from
Borneo (e.g., mammals), and much older biogeographic
elements that are nested within Philippine radiations
and represent old dispersal events from the oceanic portions of the archipelago. In this sense, the slender island
of Palawan represents a true biogeographic novelty, literally a crossroads spanning the most prominent biogeographic boundary in the world and one of the exceptions
to expectations based on Wallace’s and Huxley’s Lines.
An additional class of exceptions to the PAIC-centric
tradition of biogeography in the Philippines is the increasingly prevalent pattern of micro-endemism on small
land bridge islands. Because small land bridge (or even
deep-water) islands next to the larger land masses in the
Philippines were expected to possess a nested subset of
species diversity observed on large neighboring islands,
they have often gone unsurveyed and unscrutinized by
biologists. Many of these tiny, seemingly irrelevant islands
are now known to harbor endemics, some of which are
spectacularly divergent evolutionary novelties. Examples
include Lubang, Camiguin Sur, Dinagat, Siargao, Sibuyan,
and the Gigante Islands. All demonstrate extensive levels
of endemism, commensurate with their status as deepwater minor subcenters of diversity. Recent work suggests
that our collective knowledge of these minor subcenters of
Philippine biodiversity is far from complete.
A final exception to the prevailing paradigm of PAIClevel partitioning of biodiversity of the Philippines is an
emerging pattern of autochthonous speciation on the large
islands. Numerous recent phylogenetic studies involving
amphibians, reptiles, shrews, bats, rats, birds, plants, and
insects have drawn attention to patterns of endemism within
the large islands of Luzon, Palawan, Mindanao, Negros,
Panay, and Samar-Leyte. These studies provide evidence
of evolutionary and ecological processes (e.g., other than
rising sea level vicariance) fueling diversification. Many of
these are very interesting because they provide support for
adaptive evolution, sympatric, and/or ecological speciation
within larger islands. As such, these examples stand in contrast to the “passive” process of non-adaptive divergence
following isolation inferred for the diversification of many
other groups of species in the archipelago.
HUMAN HISTORY AND IMPACT
Colonizing from mainland Asia, humans first arrived in
the Philippines many thousands of years ago. Before the
arrival of the Spanish (sixteenth century), the Philippines
was 90–95% forested, with only scattered settlements surrounding various coastal areas. Despite a growing population and a great demand for timber, the next 300 years
probably resulted in the loss of only an additional 20%
of forest cover. We know that at the turn of the twentieth
century, Cebu Island (Ferdinand Magellan’s capitol) was
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almost completely deforested and that nearby islands of
Negros, Guimaras, and Panay were covered by less than
half of their original forest area. But other islands maintained vast expanses of intact forest, and perhaps as much
as 70% of the country’s forest persisted. The industrial
and agricultural revolution, periods of American and
Japanese occupation, plus the period of economic expansion following World War II took an extremely heavy toll
on Philippine forests. During this the last century, it is
estimated that the Philippines lost between 50% and 70%
of its original forest cover.
During this post-war period, many factors weighed
heavily on Philippine biodiversity, including high human
population growth associated with the industrial revolution (and a concomitant application of low-level pressure
on forests; Fig. 8), a long tradition of colonial control and
exploitation, shortcomings in the country’s (U.S.-installed)
education system, crippling poverty in many undeveloped
portions of the country, and chronic government graft
FIGURE
8 Primary
causes of deforestation in the Philippines:
(A) Large-scale commercial logging was introduced to the Philippines
by the Americans. In this image, loggers use refurbished World War II
weapons carriers to skid mature hardwood trunks from lowland forest of Mt. Busa, South Cotobato Province, southern Mindanao Island.
(B) Small-scale timber poaching and clearing of land for agricultural
purposes. Kaingineros like this man from Mt. Malinao, Albay Province,
Luzon Island, routinely clear small patches of forest, burn debris, and
then plant a single crop of rapidly-growing vegetables for sustenance
and sale at local markets. Photographs by Rafe M. Brown.
730
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and corruption that have pandered to a wealthy elite and
foreign hegemony.
However, by far the most destructive force has been
unchecked environmental destruction associated with largescale logging and mining. Large-scale logging and mining
were introduced to the country during the American occupation. Over the last century, the Philippines has been the
target of wholesale exploitation of natural resources combined with wide-scale plantation-style agricultural efforts
(principally hemp, bananas, copra, and sugar cane), which
have converted many of the country’s most fertile natural
ecosystems into monoculture and barren wasteland. The
end result of this unchecked colonial rule and political
instability has been systematic exploitation of Philippine
natural resources, and catastrophic environmental destruction at rates exceeding those almost anywhere on the planet.
Originally >90% forested, the Philippines now retain only
4–8% of its original old-growth forest.
CONSERVATION PROSPECTS AND
CHALLENGES FOR THE FUTURE
The Philippines shares only with Madagascar the distinction of being both a megadiverse country and a Global
Conservation Hotspot. Despite a greater understanding
of Philippine biodiversity gained during the past 15 years,
such knowledge is accumulating too slowly to conserve
and stem the loss of the archipelago’s spectacular biodiversity. There can be no doubt: the Philippines is of the
planet’s highest conservation priorities.
Part of the roots of the global conservation crisis currently
unfolding in the Philippines is related to the so-called Linnaean shortfall: the disparity between where taxonomists
have focused their attention over the last 400 years (e.g., predominantly vertebrates, selected insect groups, and angiosperms) and where the greatest proportions of undescrbed
biodiversity remain to be studied (invertebrates, other plants,
parasites, and soil microbes, among many other groups).
The Linnaean shortfall represents a failure of taxonomy and
at the same time a tremendous opportunity for future generations of researchers who choose to focus their attention
on these lesser-known groups. Nevertheless, because a lack of
knowledge of biodiversity in part contributes to its wanton
exploitation and neglect, the end result of this ignorance is
biodiversity loss and extinction.
Despite these bleak assessments, there is increasing cause
for hope and renewed efforts towards fostering sustainable
development, ecosystem restoration, and reliance on renewable natural resources (e.g., nontimber forest products such
as rattan). The National Integrated Protected Areas System
(NIPAS) Act has established a protocol for the establish-
PHILIPPINES, BIOLOGY
4/30/09 10:42:08 AM
ment and support of nationally protected areas, and establishment of new parks continues to this day at a growing
rate. Grassroots community environmentalism has sprung
up throughout the country, and a growing protectedarea system continues to spread coverage and jurisdiction
over the remaining forested regions. The country’s National
Commission on Indigenous Peoples has taken a strong
leadership role in protecting natural resources through management of tribal ancestral homelands, and an expanding
base of young, energetic conservation biologists have enthusiastically taken up the battle to protect the country’s natural
heritage. There is great cause for hope in Philippine conservation, and unique Philippine flagship species (Fig. 9) play
an increasingly important role in spreading environmental
awareness to the Filipino public.
An understanding of Philippine biodiversity will be
greatly enhanced by renewed, vigorous attention to four
primary avenues of conservation-related research. First and
foremost, these include a need for large-scale, countrywide,
and faunistically comprehensive surveys of the remaining
natural habitats of the Philippines. Great progress has been
made by a handful of researchers over the past 20 years, but
this progress needs to be increased by an order of magnitude in both scope and urgency. The next several decades
must see a massive resurgence in biodiversity studies if the
Philippine conservation crisis (and expected catastrophic
extinction event) is to be averted. Second, thorough taxonomic revisionary studies will be required to avert the Linnaean shortfall in the Philippines and promote biodiversity
conservation as a global priority. This field of study is surprisingly thankless and increasingly threatened by changing academic landscapes and emphasis on “high-impact”
publications in science. Third, the future is very bright
for molecular phylogenetic studies of endemic Philippine
radiations. Many of the truly spectacular Philippine radiations have gone unstudied. A much-needed synthesis of
geological evidence and time-calibrated phylogenetic studies shows tremendous promise for exposing the temporal
framework for evolutionary diversification of Philippine
biodiversity. Finally, for a variety of reasons, it is clear that
the future of biodiversity research and conservation in the
Philippines is an effort that must be led by Filipinos. For
this to occur, public and government perception of biologists, societal values, and educational emphasis must all
shift to endorse the preservation of natural resources and
environmental quality. Aside from their inherent value, biodiversity, forested ecosystems, and environmental health all
provide societal services such as clean water, food, renewable resources, and buffering from inclement weather.
Filipinos have a rich cultural and historical legacy that is
tightly linked to their natural heritage through these natural resources. These must all be celebrated and preserved
for future generations.
FIGURE 9 Flagship species of Philippine biodiversity conservation
and symbols of an emerging surge in environmentalism: (A) the
poorly-known Philippine tarsier, Tarsius syrichta; (B) the largest eagle
in the world, the Philippine “monkey-eating” eagle, Pithecophaga jefferyi. Photographs by Rafe M. Brown.
SEE ALSO THE FOLLOWING ARTICLES
Borneo / Frogs / Indonesia, Biology / Madagascar / Philippines,
Geology / Sustainability / Wallace’s Line
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FURTHER READING
Brown, R. M. 2007. Introduction, in Systematics and zoogeography of
Philippine Amphibia. R. F. Inger. Kota Kinabalu, Malaysia: Natural
History Publications, 1–17.
Brown, R. M., A. C. Diesmos, and A. C. Alcala. 2002. The state of
Philippine herpetology and the challenges for the next decade. The
Silliman Journal 42: 18–87.
Catibog-Sinha, C. S., and L. R. Heaney. 2006. Philippine biodiversity:
principles and practice. Quezon City, Philippines: Haribon Foundation
for Conservation of Natural Resources.
Collar, N. J., N. A. D. Mallari, and B. Tabaranza, Jr. 1999. Threatened birds
of the Philippines. Makati City, Philippines: Bookmark, Inc.
Department of Environmental Resources and United Nations Environment Programme. 1997. Philippine biodiversity: as assessment and action
plan. Makati City, Philippines: Bookmark, Inc.
Diesmos, A. C., R. M. Brown, A. C. Alcala, R. V. Sison, L. E. Afuang, and
G. V. A. Gee. 2002. Philippine amphibians and reptiles, in Philippine
Biodiversity Conservation Priorities: a Second Iteration of the National
Biodiversity Strategy and Action Plan. P. S. Ong, L. E. Afuang, and R. G.
Rosell-Ambal, eds. Quezon City, Philippines: Department of the Environment and Natural Resources, 26–44.
Environmental Center of the Philippines Foundation. 1998. Environment
and natural resources atlas of the Philippines. Manila, Philippines: ECRF.
Hall, R. 1998. The plate tectonics of Cenozoic SE Asia and the distribution of land and sea, in Biogeography and geological evolution of southeast
Asia. R. Hall and J. D. Holloway, eds. Leiden: Brackhuys, 99–132.
Mallari, N. A. D., B. R. Tabaranza, Jr., and M. J. Crosby. 2001. Key conservation sites in the Philippines. Makati City, Philippines: Bookmark, Inc.
Posa, M. R. C., A. C. Diesmos, N. S. Sodhi, and T. M. Brooks. 2008.
Hope for threatened tropical biodiversity: lessons from the Philippines.
BioScience 58: 231–240.
PHILIPPINES, GEOLOGY
GRACIANO YUMUL, JR., AND CARLA
DIMALANTA
University of the Philippines, Quezon City
KARLO QUEAÑO
Department of Environment and Natural Resources,
Quezon City, Philippines
EDANJARLO MARQUEZ
University of the Philippines, Manila
Island arc systems such as the Philippines are produced
through accretion brought about by collision of geologic
blocks, resulting in volcanism and emplacement of crust
and mantle fragments on land. The various igneous,
sedimentary, and metamorphic rock types in island arcs
reflect the complex processes involved in their generation
and evolution. Island arc-related processes involve interactions of geological features (e.g., trenches, volcanoes, and
faults) that result in specific tectonic evolution, geologic
hazards, and mineral deposits.
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GEOLOGIC AND TECTONIC SETTING OF
AN ISLAND ARC SYSTEM
The Philippines, an arc system lying off the Asian land mass,
is trapped at the margins of the Eurasian–Sundaland and
the Philippine Sea Plates. The northwest-southeast oblique
convergence between these plates is currently being absorbed
by two oppositely dipping subduction zones, namely (1) the
Manila–Negros–Sulu–Cotobato trench system along which
the marginal basins (i.e., South China Sea, Sulu Sea, and the
Celebes Sea) on the eastern edge of the Eurasian–Sundaland
Plate are being subducted west of the Philippine arc, and
(2) the East Luzon Trough–Philippine Trench system, along
which the West Philippine Basin of the Philippine Sea Plate
is being subducted east of the arc (Fig. 1).
The subduction zones extend approximately 1500 km,
delineating an approximately 400-km-wide, seismically
active deformed zone known as the Philippine Mobile Belt
within the archipelago. Intense deformation also affects different parts of the Philippine Mobile Belt with the activity
of the Philippine Fault Zone (Fig. 1). This major left-lateral
strike-slip fault system transects the archipelago for more
than 1200 km, from northwestern Luzon to eastern
Mindanao. It has both transpressional and transtensional
components and both horizontal and vertical displacements. Several major strike-slip faults branch out from the
main trace of this major fault system. These faults and fault
segments can be recognized on the basis of displacements in
exposed rock sequences, fault scarps, sag ponds, and pressure ridges. Linear features on aerial photographs, satellite,
and remote sensing images also serve to define these faults.
The Philippine Fault Zone, which formed during the
Middle Miocene, accommodates the lateral component
corresponding to the excess stress resulting from the
oblique convergence between the Philippine Sea Plate
and the Philippine Mobile Belt through shear partitioning mechanism.
Data obtained from the Global Positioning System
networks within the Southeast Asian region have provided measurements of the convergence rate between the
Sundaland–Eurasian margin and the Philippine Sea Plate.
The Sunda block to the west of the Philippine archipelago
is moving with respect to Eurasia at around 10 mm/year
in the direction 78° east of south along its northern margin and ∼6 mm/year toward 61° east of south along its
southern portion. On the eastern side, the Philippine Sea
Plate is moving northwestward at approximately 7 cm/
year in the region northeast of Luzon and around 9 cm/
year southeast of Mindanao (see inset in Fig. 1).
The Manila Trench on the western part of the archipelago continues on as collision zones in the central
PHILIPPINES, GEOLOGY
4/22/09 3:34:02 PM