Luzon has never been connected to mainland Asia. Even when glacial advances during the Pleistocene caused sea levels to fall over 100 meters worldwide, this only connected Luzon to the modern islands of Polillo, Marinduque, and Catanduanes. At least 15 million years ago, friction between the Australian and Asiantectonic plates and volcanic activity created parts of the Luzon highlands, which over the next 10 million years morphed into their modern form.[2] This long period of isolation and complex internal geography is a primary cause for the great biodiversity and high degree of endemism found on the island of Luzon.[4]
Climate
In some areas, annual rainfall can be about quadruple what the lowland rainforests receive (as high as 10,000 mm).[3] The Sierra Madres have very mild seasons, with a slight dry period between December and April. The Zambales Mountains and northern Central Cordillera highlands are more strongly seasonal with a longer dry period and slightly less rainfall generally.[3]
The dipterocarp trees of the lowlands are gradually replaced by oak and laurel forest species with increasing altitude.[3] The forests generally have less undergrowth and become shorter in stature as altitude increases.[3] With the decreasing temperature from increasing altitude, decomposition is slowed and results in a forest floor thick with humus.[3]
In the montane forests, epiphytes, vines, and moss-covered branches are very common.[3] The highest altitudes of montane forests are caller upper montane forest, or elfin forest, and are more extreme: trees are shorter in stature, and tree branches are so thick with moss and organic material that they can sustain aerial plants that are not typically epiphytes.[3] Many endemic animal species reside in the thick, matty soil of the upper montane forests.[3]
There are at least 31 endemic species of mammals on the island of Luzon.[5] Sixty-eight percent of all known native non-flying mammals are endemic to the area (23 of 34).[4]
The Philippine eagle (Pithecophaga jefferyi) is the second-largest eagle in the world found primarily in the Sierra Madre mountain range of Luzon.[5][6] Primary lowland rainforests of the Philippines have been heavily deforested, and the Philippine eagle needs this area to breed, as well as nesting in large trees and hunting within the trees.[5][6] The eagle is restricted to the islands of Luzon, Samar, Leyte, and Mindanao.[6] Attempts for captive breeding have been unsuccessful and it is estimated that less than 700 individuals remain.[5]
Often called Myer's snake in honor of Dr. George S. Myers, the genus Myersophis represented only by the species alpestris is a snake found only in the northern highlands of Luzon.[7]
Opening in jungle canopy at Mount Makiling
About sixty-eight percent of all nativereptiles are endemic to the area (about 160 of 235).[5] The Philippine crocodile, Crocodylus mindorensis, is a freshwater crocodile that is considered the most threatened crocodile in the world and is endemic to the area; it is only found in Mindanao, Negros, and Luzon.[8] Wild populations in 1982 totaled somewhere between 500 and 1000 individuals.[5] In 1995, this number decreased to a mere 100 individuals.[5] The discovery of a population of this crocodile in the Northern Sierra Madre on Luzon gives hope for its conservation.[8] Active in the conservation of Crocodylus mindorensis is the Crocodile Rehabilitation Observance and Conservation (CROC) Project of the Mabuwaya Foundation.[5]
Conservation
A 2017 assessment found that 3,813 km2, or 46%, of the ecoregion is in protected areas.[1] Protected areas in the Luzon montane rain forests include:[9]
^ abEric Dinerstein, David Olson, et al. (2017). An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm, BioScience, Volume 67, Issue 6, June 2017, Pages 534–545; Supplemental material 2 table S1b. [1]
^ abcdRickart, E. A.; Heaney, L. R.; Balete, D. S.; Tabaranza, Jr. (2010). "Small Mammal Diversity Along An Elevational Gradient In Northern Luzon, Philippines". Mammalian Biology - Zeitschrift für Säugetierkunde. 76 (1): 12–21. doi:10.1016/j.mambio.2010.01.006.
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