The role of fire on land cover changes in Borneo Andreas Langner and Florian Siegert 1 Abstract Borneo has experienced heavy deforestation, forest degradation and repeated disastrous forest fires during the past two decades. In this study the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to monitor land cover changes in Borneo between 2002 and 2005 in order to assess the current extent of the forest cover, the deforestation rate and the role of fire in deforestation. Using Landsat and ground observation for validation it was possible to discriminate 11 land cover classes in cloud-free MODIS image mosaics. In 2002 57% of the land surface of Borneo was covered with forest of which 74% was lowland dipterocarp forest and 23% peat swamp forest. The average deforestation rate between 2002 and 2005 was 1.7% per year. The carbon rich ecosystem of peat swamp forests showed a deforestation rate of 2.2%. Almost 98% of all deforestation occurred within a range of 5 km to the forest edge. The role of fire was investigated with special emphasis on the tropical peat land areas, which are store and sink for carbon of global importance (Page et al. 2002). A complete data set of MODIS active fire detections (hotspots) for the years 2002 – 2006 was used to investigate fire occurrence in relation to land cover and the spatial pattern of the distribution of fire. Fire occurrence was highly correlated to previous forest disturbance: Most fires were detected in logged over forests, degraded forests and forest mosaics. 98% of all forest fires were detected within a 5 km zone from the forest edge. Undisturbed and undrained peat swamp forests were hardly affected by fire even under El Niño drought conditions. Our results show the importance of long term time series analysis to better understand conditions leading to recurrent forest fires in tropical rain forests underlining that fire is a major driver for forest degradation and deforestation. Furthermore our results are useful to improve fire management, fire hazard prediction and early warning in order to preserve remaining forests and the peat carbon store. Introduction The world’s tropical rain forests are highly threatened by overexploitation and forest conversion. Several studies showed that the global relative rate of deforestation is 0.5% per year. It is highest in Southeast Asia with 0.8 - 0.9% followed by Latin America and Africa both with an annual deforestation rate of 0.4 - 0.5% (FAO 2000, Achard et al. 2002, FWI and GFW 2002, Fuller 2006). Before deforestation takes place, forest degradation by logging and fire occurs as a preliminary stage (Asner et al. 2005). To the annual deforestation of 5.8 million ha of tropical rain forests worldwide adds another 2.3 million ha which get degraded per year through fragmentation, legal and illegal logging or fires (Mayaux et al. 2005). Major drivers in Southeast Asia are logging, agricultural expansion, the establishment of infrastructure and the conversion of forests into oil palm and pulp wood plantations 1 Remote Sensing Solutions GmbH, Wörthstr. 49, 81667 Munich, Germany & Department II – GeoBioCenter - Ludwig-Maximilians-Universität, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany; siegert@rssgmbh.de ; andi_langner@gmx.de