How exactly did the devils appear in the Philippines in the the 15th and 16th centuries, as compiled by Isabelo de los Reyes from old Spanish missionary documents and published as El Diablo en Filipinas (Ang Diablo sa Filipinas)? In a variety of expected ways it turned out. In August and September 1595, Fr. Aduarte reported that in the City of Nueva Segaovia, there was "spotted a mastiff of unheard-of size making several turns around the Church and adjoining houses." Fr. Aduarte conjectured that "there can be no doubt who the mastiff really was."
It was notable how, according to the documents, a local demon even predicted the coming of the new faith brought by men "dressed in long robes." And then there was the demon who made "painful pranks" to a solitary man in a forest. "The evil spirit would bring him a number of beings resembling girls. Then, either by deceitful words or force, the man would be put in the midst of some thick shrubs, where the girls would toss him into the air as if they were playing with a pelota ball. Finally, they would leave the man there half dead...."
Sometimes the chronicles also reinforced the folk beliefs and chalked them up to the devil's manipulative designs. An example was the demon jumping on top of a sick man and shutting his mouth, a phenomenon known locally as bang̃ung̃ut (nightmare). Elsewhere, the narrator and Gatmaitan read of the exploits of the demon possessing or tormenting the 'Indios' and being fought off by priests and defeated only after an extended "pitched battle."
These and many other awesome occurrences characterized the various demonic manifestations in the archipelago. Many other horrifying episodes were recounted in the book. One involved the summit of Taal Volcano sinking into the crater and accompanied by hair-raising roars, fearful voices, groans, thunderclaps, and lamentations. The devils often favored the forms of an animal: "deformed and monstrous dog," "fierce, black, and terrifying cat," and "ferocious man-eating caiman." Yet sometimes they appeared with such beautiful face and could even impersonate the figure of Christ! The devil was, then and now, so multi-talented, so spectacular.
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The idea of the devil in relation to natural environment, as recorded by the friars, was particularly interesting for the insights it gave on sustainability issues and ecological implications. Behind native beliefs in animism, concepts of natural disaster risks, extreme weather events, and ecosystems connectivity were apparent. This could be seen in one passage read aloud by Gatmaitan.
"[...] On the same page you will find something else. Don Luys Pérez Dasmariñas ... spent a night on the slope of a small hill dedicated to the demon (in Cagayan). ... No native would dare to cut down trees to make poles or anything else, except in service to this demon. If these rules are violated, then the ocean will get very rough, and the wind leap high, destroying houses... That very night the most violent of wind-storms blew high and stirred the ocean to surge over the shoreline and reach as far inland as the military billets, usually thought to be very safe under dangerous conditions. The storm obliged the soldiers and even Don Luys to flee, the latter losing a lot of his assets because he had cut down so much on 'his' hill (branches and sugar cane)." [emphases added]
Trees (mangroves or otherwise) had always been seen as a shield against typhoons. Divine, or rather devil's, retribution after violating the rules came in the form of natural disasters like storm, storm surge, and flash flood. To cut down trees was seen as an affront to the demon who dwells in a hill in Cagayan. This environmentalist folk belief, alongside its metaphysical color, was fascinating for sustaining a strategy to conserve the natural environment and prevent loss of human lives and properties.
Another instance of environmentalism in native beliefs which were perversely twisted by the friars was taken from the chronicle of Father Gaspar de S. Agustin, as read by Gatmaitan:
'In the township of Dumalag (in Panay) ... there was a gigantic tree on which uncountable numbers of small birds used to meet. They never stopped making a tremendous noise with the chirping they created, and this was a notable inconvenience for all the people of the township. But the Indios had such superstitious reverence for the tree that they would not approach it even from a considerable distance. They also refused to cut the nearby grass which they likewise regarded as sacred. They explained this custom by saying that the tree was inhabited by Divatas, deities of the forests and mountains, whom they venerated from ancient times.... Father Hernando de Morales came to the tree and carved a cross on its trunk, whereupon all the birds departed forever; even if a few people moved in, they soon fled too, because these birds were demons or [the souls of] Indios of the township, who had meetings with the demon on just that spot.' [emphases added]
The great reverence for the natural components of the ecosystem (sacred tree, sacred grass, hill, birds) was consistent to the beliefs of several indigenous groups in the Philippines. The Molbog tribe in Balabac, for example, also believes in sacred trees. The preservation of these trees—specifically lu-jan and manggis —are important for the survival of their tribe. Another belief of the Molbog is for sacred sea turtles. They are particularly wary of the Leatherback turtle (Dermochelys coriacea), a critically threatened species, which they described as having ‘scales’ on the back. They believe that this turtle is the ‘king of the turtles’ and that capturing such turtle will bring bad omen.
A similar concept of taboo (bad omen) could be seen in the indigenous beliefs on "mataw fishing" of the Ivatan in Batanes . The indigenous peoples still retained some of these beliefs even at present times due to their relative isolation and insulation from the mainstream society and colonialism.
The natural history of the Devil in the Philippines showed that colonialism and environmental degradation went hand in hand. The superstitious friars targeted the old belief systems, spun stories over and around them, and encoded a new belief system. Theirs was a most efficient and effective way to propagate the new faith. Anything that appeared strange to them they labeled as originating from the "devil" even when the concept of the "sacred" was associated to divine origin. Devil or not, the spirits guarding the natural environment were evicted and the country's natural resources began to be utilized and extracted in unsustainable manner. After the disruption of spiritual balance, the overturn of ecological balance.
 Beyond cultural beliefs, there are actually ecological and economic reasons for the preservation of the Molbog "sacred trees." According to a field guide on plants by Madulid (2002), the manggis (Koompassia excelsa) is recorded only in Palawan. It is a habitat of threatened birds such as the Philippine cockatoo, the talking mynah, and blue-naped parrot. It is also a place for beehives. Some Molbog believe this tree is sacred because it stands tall over the forest canopy, and so serves as protection against typhoons, although its branches are not that strong.
Lu-jan, another sacred tree, is most probably one of the two species of wild durian (Durio testudinarum and Durio zibethinus). Both fruits are edible. D. testudinarum or Dugyan is a rare species while D. zibethinus, known as Durian or Luad, is indigenous in the Western Malayan archipelago and is cultivated in southern Philippines. The fruit of the first species serves as food for wild pigs, anteaters, and squirrels. The second species has a more palatable fruit; its edible seeds are boiled and roasted and have medicinal properties (Madulid 2002). Lu-jan, which is either or both of these trees, is probably considered sacred because it serves as food for the Molbog especially in times of hunger and days of poverty. There are few other sources of food coming from the forest except for this important tree.
 The Ivatan believed in añitu (invisible beings) who have the power and capricious nature to inflict misfortune on people. They believed in dagen (taboo) which prescribes etiquette and protocol and reveals an ethnic respect toward one’s fish catch. For instance, the ‘placing of dirt’ on fishing gear and boat and even on the hands and body of the fisherman renders him unable to catch fish. In catching dorado (dolphinfish), the fisher must be coaxing and not arrogant. The fisherman must remove the hook from the dorado’s mouth while at sea, and the dorado should be faced toward the land and their tails toward the sea when laying them on the shore. While eating lataven (kilawin), one must not spit out the bones but take them carefully from one’s mouth. There are supernatural consequences for violating dagen or not performing an important ritual. This includes the inability to catch fish or misfortune (sickness, accident, death). Breach of dagen may also affect the catches of an entire fishing group. The dagen also prescribes strategies to conserve or regulate the fishery resource use such as seasonal use rights and regulation of gear entry and individual catch quotas. [See Mangahas (1993), "Traditional Fishermen’s Associations, Indigenous Belief System, and Laws," in Indigenous Coastal Resource Management: The Case of Mataw Fishing in Batanes (Quezon City: UP Center for Integrative and Development Studies). For a historical and legal perspective on the plight of indigenous peoples, see Molintas (2004), "The Philippine Indigenous People’s Struggle for Land and Life: Challenging Legal Texts," Arizona Journal of International and Comparative Law 21(1): 269-306.]