Impact assessment of road development on forest cover in the Upper Marikina Watershed, Philippines

Abstract

Most watersheds in the Philippines are already in critical condition. One of which is the Upper Marikina Watershed (UMW), where forest cover has dwindled significantly due to land conversion as well as land use and land cover change. Road networks are being developed as a means of access and transportation to land-converted areas. However, roads are a major driver of deforestation and degradation. Therefore, this study assessed the impacts of road development on forest cover in the UMW. Specifically, it determined the extent of the road network in the watershed; described the extent of forest cover in the watershed in 2005, 2010, 2015, and 2020; analyzed changes in the forest cover of the watershed through time; and established the relationship between road network development and the changes in forest cover in the watershed. Shapefiles from the National Mapping and Resource InformationAuthority (NAMRIA) and 2020 Landsat 8 satellite images were used to generate 2005, 2010, and 2015 land cover maps to detect changes over time. The Landsat 8 satellite image was processed for image pre-processing, cloud masking, sub-setting, image classification, and accuracy assessment through remote sensing using the QGIS software and the Semi-Automatic Classification Plugin. The data on the forest cover of the site through 2005, 2010, 2015, and 2020 were analyzed through Change Detection Analysis. This analysis was used in correlation with the existing road network within the watershed. The findings revealed a significant decrease in forest cover in the UMW between 2005 and 2020. All these changes in forest cover due to further land conversion in the area create opportunities for road network development and expansion, which are inversely correlated with forest changes.