Human-Altered Tree-Based Habitats and Their Value in Conserving Bird and Bat Diversity in Northeast Luzon, The Philippines - Smallholder Tree Growing for Rural Development and Environmental Services - page 335

It is well established that biodiversity in the Philippines is under severe threat, and
several well-monitored species have reached dangerously low population levels
and continue to decline (e.g. WCSP 1997; Heaney and Regalado 1998; Collar et al.
1999; IUCN 2006) supporting the time gap hypothesis.
Perhaps surprisingly, very little information is available to assess hypothesis
three. Nearly all biological attention in the Philippines is still devoted to taxonomy,
biogeography and basic biodiversity surveys in forested areas. However, Posa and
Sodhi (2006) report that in the Subic Bay area of Luzon a number of forest birds
and butterflies, including endemic species, were found in disturbed open canopy
forest and non-forest habitats although forest species richness declined with
urbanisation.
16.1.3 ResearchObjective
The objective of this study is to determine the conservation value of smallholder
tree-based systems for birds and bats in the human-altered landscape of the
Cagayan Valley.
16.2 Methods
16.2.1 StudyArea
Fieldwork was conducted in Isabela and Cagayan Provinces of Region II. This
region is reported to have a forest cover of 11,498 km 2 (43 percent of the region's
area and 16 percent of the country's total remaining forest cover), including ca.
336 km 2 of forest plantations (Forestry Management Bureau 2004). Forest planta-
tions in Region II are mainly composed of monoculture Gmelina arborea (M. van
Weerd and D. Snelder, personal observation 2005).
Survey localities were situated in the human-altered landscape extending from
the intensively cultivated lowland areas along the Cagayan River in the West to the
contiguous closed-canopy Dipterocarp forest in the Sierra Madre Mountain Range
in the East. The lowland areas are mainly used for monocultures of rice, corn and
tobacco. Towards the hilly uplands land use gradually changes into grassland and
corn fields, with banana and forest patches on steeper slopes. The mountains run
parallel to the eastern coast of northern Luzon and reach elevations of just under
1,900 m. They are still largely covered with tropical forest, yet mostly selectively
logged in areas up to 1,000 m. In 1997, an area of 3,607 km 2 in the Sierra Madre in
Isabela Province was declared a protected area: the Northern Sierra Madre Natural
Park (NSMNP). An additional area of ca. 2,500 km 2 north of the NSMNP in Cagayan
Province is also protected as the Penablanca Protected Land and Seascape.