The Northern Sierra Madre Natural Park (NSMNP) is within the Sierra Madre Biogeographic Zone (SMBGZ) which lies along the eastern side of Central Luzon. The Northern Sierra Madre Natural Park (NSMNP) is one of the ten (10) priority protected areas in the country. The Northern Sierra Madre Natural Park (NSMNP) is considered one of the most important of the protected areas system of the Philippines. It is the largest protected area in the country and the richest in terms of genetic, species and habitat diversity. The importance of the park is underscored by the myriad of rare and endangered species of flora and fauna that it supports. These include Philippine Eagle (Pithecophaga jefferyi ), Golden Crowned Flying Fox (Acerodon jubatus ), Philippine Eagle-Owl ( Bubo philippensis), Isabela Oriole (Oriolus isabellae ), Green Sea Turtle ( Chelonia mydas), Loggerhead Turtle ( Caretta caretta ), Hawksbill Turtle (Erethmochelys imbricata), Philippine Crocodile (Crocodylus mindorensis ) and Dugong ( Dugong dugon ).
The Sierra Madre Mountain Range system provides the area for growth and development of unique habitats and their associated flora and fauna, e.g., grasslands to mountain forests, which is among the most unique and richest on a per area basis among the park systems in the Philippines. It is described as long mountain chain providing habitats for the numerous species of plants and animals adapted to various ecological niches.
The NSMNP is habitat to many endemic and rare species of plants. Among the endemic plants in the park are the various species of the dipterocarp family such as Shorea spp. and Hopea spp., various orchids such as Dendrobium aclinia, the leguminous tree, Milletia longipes and a member of the citrus family, Swinglea glutinosa.
The Northern Sierra Madre Natural Park, also known as the Palanan complex or Wilderness Area, is in eastern Isabela Province, in the northern half of the Sierra Madre Mountain Range. It is bounded by the Dikatayan River to the north, the Disabungan River to the south, the Cagayan Valley to the west and the Philippine Sea to the east. The topography within the park ranges from relatively low hills with moderately steep slopes near the coast to higher mountains with very steep slopes, peaks and sharp ridges in the interior of the Sierra Madre Mountain Range. A series of peaks along the north to south range running through the park rise to well over 1,000 m, including Mt Cresta (1,672 m), Mt Divilacan (1,311 m), Mt Palanan (1,184 m) and Mt Dipalayag. The limestone area south of Palanan Point exhibits a karst topography, with knobby hills and numerous depressions. The park is unique on Luzon in the extent of undisturbed lowland dipterocarp rainforest, and because it includes areas where undisturbed forest extends from the coast to the mountain peaks. There are some extensive areas of montane forest around the higher peaks in the park, and forest over limestone, forest AND over ultramafic rocks. The large tracts of primary forest that remain intact in this part of the Sierra Madre Mountains are a complete contrast to the adjoining Cordillera and Caraballo mountain ranges, which are heavily deforested and degraded. The rivers and streams that flow from the park’s extensive forests are one of the main sources of water for domestic, agriculture and industrial use in northeastern Luzon. Along the park’s coastline are other ecosystems, which are among the most diverse and productive in the world. These include estuaries, mangroves, beach forest, seagrass-beds, and coral reefs. They are particularly important as nesting grounds for some threatened endemic birds, turtles, and estuarine crocodiles, or as spawning and nursery area for many commercially important fishes, crabs and shrimps. The attractive scenery and beaches of this IBA have great potential for tourism. Most of the inhabitants in this IBA are immigrants (and the descendants of immigrants) from nearby provinces, and from as far as the Bicol and Visayas regions. There are at least 1,000 indigenous Agtas, who practice a nomadic lifestyle in the park. The mineral reserves in this protected area include copper, gold, manganese, chromite, zinc, nickel and possibly uranium. Some of the main deposit areas are in Palanan, San Mariano and Dinapigue.