Abstract
Southeast Asia experienced higher rates of deforestation than other continents in the 1990s and still was a hotspot of forest change in the 2000s. Biodiversity conservation planning and accurate estimation of forest carbon fluxes and pools need more accurate information about forest area, spatial distribution and fragmentation. However, the recent forest maps of Southeast Asia were generated from optical images at spatial resolutions of several hundreds of meters, and they do not capture well the exceptionally complex and dynamic environments in Southeast Asia. The forest area estimates from those maps vary substantially, ranging from 1.73×106 km2 (GlobCover) to 2.69×106 km2 (MCD12Q1) in 2009; and their uncertainty is constrained by frequent cloud cover and coarse spatial resolution. Recently, cloud-free imagery from the Phased Array Type L-band Synthetic Aperture Radar (PALSAR) onboard the Advanced Land Observing Satellite (ALOS) became available. We used the PALSAR 50-m orthorectified mosaic imagery in 2009 to generate a forest cover map of Southeast Asia at 50-m spatial resolution. The validation, using ground-reference data collected from the Geo-Referenced Field Photo Library and high-resolution images in Google Earth, showed that our forest map has a reasonably high accuracy (producer's accuracy 86% and user's accuracy 93%). The PALSAR-based forest area estimates in 2009 are significantly correlated with those from GlobCover and MCD12Q1 at national and subnational scales but differ in some regions at the pixel scale due to different spatial resolutions, forest definitions, and algorithms. The resultant 50-m forest map was used to quantify forest fragmentation and it revealed substantial details of forest fragmentation. This new 50-m map of tropical forests could serve as a baseline map for forest resource inventory, deforestation monitoring, reducing emissions from deforestation and forest degradation (REDD+) implementation, and biodiversity.
Highlights
Dramatic changes in forests, especially tropical forests, have significant impacts on regional climate, water and carbon cycles as well as biodiversity [1,2]
The producer’s accuracy and the user’s accuracy of forest were 86% and 93%, respectively, which indicates that the accuracy of the Phased Array Type L-band Synthetic Aperture Radar (PALSAR)-based forest map at 50-m resolution was good and the PALSAR mosaic data performs well in continentally consistent forest mapping, which could be partly attributed to the simple classification scheme
Tropical forests play an important role in the carbon cycle, biodiversity conservation, and other ecosystem services closely related to human well-being
Summary
Dramatic changes in forests, especially tropical forests, have significant impacts on regional climate, water and carbon cycles as well as biodiversity [1,2]. As the third largest area of tropical rainforests in the world following the Amazon and Congo Basin [4,5], Southeast Asia experienced more dramatic deforestation than any other continent in annual rate in the 1990s [6]. This region was a hotspot of forest cover change from 2000 to 2010, e.g., Margono et al [7]. To support regional sustainable development, including forest management, carbon emission estimation, habitat planning, and biodiversity conservation, it is critical that accurate and updated information on forest area, extent, fragmentation and change is developed [13,14]
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