Sierra Madre is largely defined by the Sierra Madre mountain range traversing the provinces of Cagayan, Isabela, Quirino, Nueva Vizcaya up north; Aurora, Nueva Ecija, Bulacan in Central Luzon; and Rizal, Laguna, Quezon, and all the way to the Bicol region in the south. It contains the largest remaining tract of old-growth tropical rainforest in the Philippines which is about 1.4 million hectares of forest, representing 40% of the country’s forest cover. Being the longest mountain range in the country, it is also known as the “backbone of Luzon.”

The biological importance of the corridor is not only due to its remaining intact forest in the central part of the mountain range, but also to its megadiversity. The Sierra Madre forests are home to hundreds of wildlife species, many of which are unique to the Philippines, including the Philippine eagle and golden crowned flying fox. It is not only rich in species diversity and endemism, but also home, pharmacy and more importantly a sacred ground and cathedral to many indigenous peoples.

The Sierra Madre mountain range is also one of the major drivers of the Philippine economy, as its watersheds provide services that support major infrastructure, including dams that irrigate thousands of hectares of farm lands in Central Luzon and the Cagayan Valley region (the “rice bowl” of the Philippines), as well as water utilities and power plants that supply Manila, the capital and industrial center of the Philippines.

No wilderness, in the Philippines, equals the Sierra Madre, with its vast and rare swath that stretches from the mountains to the ocean. But the ecological interdependence of its terrestrial, coastal, and marine ecosystems hangs in a fragile balance and faces the risk of extinction.

The Sierra Madre Mountain Ranges continue to experience forest degradation despite the national and international campaign to preserve the environment. Logging remains the primary reason for this sad state of Sierra Madre. In addition, human encroachment and associated timber poaching, mining, conversion of forests for agriculture, and migration as well as development, particularly, road construction that will improve access and subsequent potential for exploitation of the area and proposed construction of more mega-dams also threaten its entire ecosystem and the lives of its stakeholders. By and large, corruption, poor implementation of environmental and forest protection laws, and lack of alternative livelihood for many poor people contribute to its continued degradation.