XIV WORLD FORESTRY CONGRESS, Durban, South Africa, 7-11 September 2015 Potential use of synthetic aperture radar in detecting forest degradation in the protected areas of the Philippines: a case study of Sibuyan island Roven Tumaneng1, Angelica Kristina Monzon1, Joanne Rae Pales1, and Jose Don de Alban1 1Fauna & Flora International - Philippines, [email protected], Tagaytay City, Cavite, Philippines Abstract With the forest of the Philippines under intense pressure, one of the innovative ways of detecting and monitoring deforestation and forest degradation aside from using optical imagery is using radar images such as Synthetic Aperture Radar (SAR) data. This study aims to recognise the potential use of SAR technology in the Philippines for determining the extent of deforestation and forest degradation particularly in protected areas. One of the identified protected areas that are being degraded at an alarming rate is Mt. Guiting-guiting Natural Park (MGGNP) in Sibuyan Island, Romblon. Dual-polarised L-band ALOS/PALSAR mosaic data at 25-meter spatial resolution, taken at two acquisition years (2007 and 2009), were utilised in this study to provide information on forest cover and habitat change in Sibuyan Island between year 2007 and 2009. In-situ data was used for forest/non-forest classification and 15 habitat transects were surveyed to identify the different habitat types using Mallari et al.’s (2011) broad habitat types (4 classes) and used to train and validate it. Results showed that there is moderate to severe degradation of old growth forests (at the rate 24% between 2007-2009) as seen in land cover change detection models while the annual deforestation rate in the island was computed at 0.36%. It indicates that the forest cover almost remained unchanged from that span of 2 years but the rate of degradation is significantly increasing evinced by the decrease in extent of old growth forest whilst gaining early secondary growth forest. Some of the major identified causes of forest degradation in the island is due to unregulated harvesting of forest resources such as fuel wood, charcoal and poles/post, unregulated opportunistic logging and unsustainable harvesting of non-timber forest products. Overall classification accuracies achieved using Mallari et al.’s (2011) broad habitat types at 70.29% and 69.70% for 2007 and 2009 PALSAR data, respectively. Keywords: ALOS/PALSAR, forest degradation, habitat change, protected area management, change detection, forest monitoring Introduction, scope and main objectives Philippines have a numerous protected areas, estimated to cover about 25, 995 km2, or 87% of the country’s area (Ong et al., 2002). Although each protected area in existence is very important, much more needs to be done particularly on monitoring its forest area. On the other hand, information on forest classification, extension, degradation, biomass, and temporal evolution of forest areas is therefore tremendously requested, especially in regions with scarce accessibility (Petinatto et al. 2014). Remote sensing has become a useful and important tool for evaluating the implementation of environmental policies and decision-making (Mayer and Lopez, 2011). Together with standardized ground plots and regular in situ measurements, remote sensing is a powerful monitoring device as well especially on land cover/forest habitat change detection and identifying change hotspots. Earth observation data have been used in the past (c. since 1970s) in the Philippines for national and sub-national forest cover mapping, mainly by applying visual interpretation techniques on optical (multispectral and hyperspectral) satellite data (e.g., Landsat, SPOT, etc.) (Swedish Space Corporation, 1988; Kummer, 1992). However, persistent cloud cover and inclement weather conditions in the Philippines limits the utility of optical/multispectral data that can be used for either wall-to-wall or even site- level land cover mapping and consistent forest change monitoring. The Japan Aerospace Exploration Agency’s (JAXA) Advance Land Observing Satellite (ALOS) Phased Array L band Synthetic Aperture Radar (PALSAR) provided an opportunity to utilise synthetic aperture radar (SAR) as a suitable alternative data source to overcome these limitations of optical/multispectral data. SAR is a side-looking active remote sensing system, which transmits microwaves and receives measurements from the signal backscattered from a surface, to produce an image after appropriate processing (Wheeler et al. 2014). The main benefit of SAR its ability of its sensor, day- and night-time imaging capability and independence from weather conditions and solar illumination. SAR imaging has been available in remote sensing since 1951 (Almeido-Filho et al. 2009), and its applications cover a wide range in mapping and monitoring of natural resources. Moreover, its capability has been effective for periodic forest monitoring and change detection (Rosenqvist, et al. 2010; Rahman and Sumantyo, 2010). SAR data are available internationally from a large number of satellites with different frequency bands, polarizations, and variable imaging geometries (Walker et al. 2010). Longer wavelength L-band SAR, such as ALOS/PALSAR, have been demonstrated to be suitable for monitoring forest and wetland areas largely because of its sensitivity to vegetation (Almeido-Filho et al. 2009; Walker et al. 2010; Rosenqvist et al. 2010) This study focuses on the potential of using SAR to map and delineate forest cover in Sibuyan Island. This paper also provides the ability of SAR to distinguish vegetation-based habitat categories and the use of remote sensing for assessing the conservation status of habitat types. Study Area and Data A. Study Area Sibuyan Island is the second largest island of Romblon Province with an approximate land area of 45,600 has. The Islands of Marinduque, Panay, Masbate and Tablas surround the island. Sloping lands dominate the topography of the area. Approximately, 77% of the land is considered to have a slope of 18% and above. The highest peak in the island is located at Mt. Guiting-guiting with an elevation of 2,058 meters above sea level. Sibuyan Island is under Type III climate based on Corona’s classification, which indicates that there is no very pronounced maximum rain period in the area, and has a short dry season usually lasting from 1-3 months (March-May or December-February) (DENR- MIMAROPA, 2014). There are 3 municipalities and 36 barangays with an annual growth rate of 0.96%. Currently, the population of Sibuyan is 57,248 and a population density of 118.2/km2 (NSO, 2010). The indigenous dwellers in Sibuyan Island are called Sibuyan Mangyan Tagabukid (SMT). Two Certificate Ancestral Domain Titles (CADTs) were issued to SMT covering a total of 8,408.84 has located in two non-contiguous areas within Cajidiocan and San Fernando (Tongson & McShane, 2006). The island is recognized as one of the key biodiversity area. It was believed that many groups of plants and animals demonstrate medium to high levels of endemism because of diversification brought about by its complex geological history and long periods of isolation from other islands (Brown and Diesmos, 2009). Aside from that, this island still has high remaining forest cover. Due to its ecological importance, Sibuyan Island’s most prominent peak, Mt. Guiting-guiting has been declared Natural Park by Pres. Fidel V. Ramos under Proclamation No. 746 on February 20, 1996. The terrestrial reserve with an area of 15,260.48 hectares was mandated to be protected and conserved in a sustainable basis (DENR- MIMAROPA, 2014). In spite of its protected status, Mt. Guiting-guiting Natural Park (MGGNP) and many other natural areas on the island remain under serious threats. B. ALOS/PALSAR Data Eight dual-polarisation (HH and HV) ALOS/PALSAR image mosaics at 25-meter spatial resolution taken at two image acquisition years (2007 and 2009) were used for the forest cover and habitat assessment in Sibuyan Island, Romblon. Each tile was identified with the reference address of latitude-longitude of N13 E122 in each of the two acquisition years. Each 1x1-degree image mosaic tile (4500 x 4500 pixels) was pre-processed using Japan Aerospace Exploration Agency’s (JAXA) mosaicking algorithm, which includes calibration, orthorectification, slope correction, and intensity normalisation with neighbouring data strips (Rahman and Sumantyo, 2010). C. Field Data Figure 1: Collected ground truth points over the 2010 land cover map of Sibuyan Island, Romblon. (Data source: National Mapping and Resource Information Authority, 2010) Field data were collected during the habitat and biodiversity surveys, land cover assement and socio-economic survey conducted in three municipalities of Sibuyan Island namely, Cajidiocan, San Fernando and Magdiwang in May to June 2014. Habitat surveys were conducted using transect route. Transects comprised of a 2-kilometer line with transect points marked at every 25 meters. A total of 15 transects were surveyed covering a full range of habitat and disturbance gradients across all three sites of Sibuyan Island. Habitat types was identified for every transect points using the broad habitat classification of Mallari et al. (2011) which consists of four habitat categories: old growth forest, advanced second growth forest, early second growth forest, and cultivated areas (Table 1). These habitat categories will be used in generating supervised classification of the ALOS/PALSAR mosaic images of 2007 and 2009.