Space-based detection of peatlands ’ landcover changes and its impact on coastal erosion Muhammad Haidar #*1 , Koichi Yamamoto #2 Noerdin Basir ”3 Ariyo Kanno #4 Masahiko Sekine #5 # Graduate School of Science and Engineering Yamaguchi University Tokiwadai, Ube City - Yamaguchi 7558611, Japan * Thematic Mapping Division, Geospatial Information Agency of Indonesia Jl. Raya Jakarta-Bogor Km 46 Cibinong 16911, Indonesia ” Politeknik Negeri Bengkalis Jl. Bathin Alam, Sungai Alam, Bengkalis Riau 28711, Indonesia 1 muhammad.haidar@big.go.id 2 k_yama@yamaguchi-u.ac.jp 3 noerbas@gmail.com 4 kanno@yamaguchi-u.ac.jp 5 ms@yamaguchi-u.ac.jp Abstract—Increased demand or pressure on land resources inevitable shows up and considerably contribute to peatland and forest degradation. In recent decade the degradation of Indonesian peatland and forest has dramatically increased especially in Sumatera and Kalimantan islands. The aim of this research is to assess the impact of peatland landcover change on coastal erosion. Bengkalis Island as part of Sumatera was selected as research area because of the unique geomorphologic process occurred (coastal peatland erosion and sedimentation) and almost the entire island covered by peat. The research area was focused on the western half section of Bengkalis Island where erosion took place in the northern coast and sedimentation in the western coast. In this research we employed 4 Landsat medium resolution satellite images observed in different period of time (1988, 1997, 2008, and 2013). The extent of coastal erosion and sedimentation could be identified using multi temporal images and subsequently calculated its volume using corrected SRTM data for certain time span. Our preliminary results reveal that mangrove cutting for wood fuel and construction material leads to severe coastal erosion and then partly accumulated alongside the western coast. We estimated total erosion extent at 681.41 ha representing a loss of 0.75% from the total area of Bengkalis Island in the 25 years between 1988 and 2013 in northern coast and contributing at 158.52 ha on coastal sedimentation. Erosion and sedimentation rates varied both spatially and temporally with variations possibly due to differences in landcover change patterns. Keywords— remote sensing, peatland, landcover change, coastal erosion I. INTRODUCTION Sumatra Island, Indonesia, contains around 72,000 km 2 of peatlands areas that have experienced extensive degradation and conversion over the past decades [1]. These peat deposits that can be found mainly in the Sumatera, Kalimantan and Papua coastal lowlands have been formed over thousands of years as a result of accumulation of organic material in waterlogged and usually acidic conditions. Occasionally reaching depths of up to 10 m, the peatlands of Southeast Asia form a considerable surface carbon deposit containing around 70 Giga ton of carbon [2]. However, the peat accumulation process in tropical peatlands depends on a delicate balance between hydrology, ecology and landscape morphology [3]. Changes in these components directly affect the resilience of these ecosystems. Local communities living adjacent to peatlands forest have traditionally collected fuel wood, fish and other natural resources from peatlands. However, in recent decades many peatlands areas have come under intense pressure from rapid urban and industrial development, compounded by a lack of effective governance and/or power among responsible government institutions. Peat swamp forest have been overexploited or converted to various other forms of land use, including agriculture, palm oil plantation, urban and industrial development. Analyses of the true economic value of peatlands indicate that their destruction for short term profit is usually economically irrational; in fact, the discrepancy between their value as intact systems and their value after destruction is one of the greatest for all habitats [4]. Given this market failure and the threats to this ecosystem, it is crucial to accurately determine the current extent, rates of change and distribution of peatlands to allow effective conservation planning and management. The powerful spatial processing capabilities of Geographic Information System (GIS) and its compatibility with remote sensing data have made the coastal erosion analysis more comprehensive and robust. GIS can be used to scale up to regional levels and to quantify the differences in area extent of erosion and sedimentation. The integrated use of remote sensing and GIS could help to assess erosion at various scales and also to identify areas that are at potential risk of coastal erosion. Several studies showed the potential utility of GIS