The potential of L-band SAR for quantifying mangrove characteristics and change: case studies from the tropics
Résumé
1. The Japan Aerospace Exploration Agency's (JAXA) Advanced Land Observing Satellite (ALOS) L-band Phased Array Synthetic Aperture Radar (PALSAR), launched successfully in January 2006, will provide new data sets for coastal ecosystems mapping and change monitoring at local to global scales. 2. To evaluate L-band capability for mangrove applications, data acquired by the NASA airborne SAR (AIRSAR) and Japanese Earth Resources Satellite (JERS-1 SAR) over sites in Australia, French Guiana and Malaysia were used to demonstrate benefits for mapping extent and zones, retrieving biomass and structural attributes (e.g. height), and detecting change. 3. The research indicates that mapping is most effective where mangroves border non-forested areas and where differences in structure, as a function of species, growth stage and biomass distributions, occur between zones. 4. Using L-band SAR, biomass can be retrieved up to 100-140 Mg ha-1, although retrieval is complicated by a noticeable decrease in L-band backscattering coefficient within higher (>200 Mg ha-1) biomass stands, particularly those with extensive prop root systems. 5. Change detection through multi-temporal comparison of data proved useful for mapping deforestation/regeneration and mangrove dynamics associated with changing patterns of sedimentation. 6. The research highlights the likely benefits and limitations of using ALOS PALSAR data and supports JAXA's Kyoto & Carbon (K&C) Initiative in promoting the use of these data for regional mangrove assessment.