New perspectives on global ecosystems from wide-area radar mosaics: flooded forest mapping in the tropics

Large floodplains in the tropics, like the Congo river basin in Central Afr ica, are interesting ecosystems that function as water storage and faunisti c and florensis habitat. Moreover, they host a series of bio-chemical proce sses, such as methane emission, which have a significance in global change issues. Characterization of these complex ecosystems can be tackled from di fferent view points, such as bio-chemistry, geology, climatology, hydrology , geomorphology, floristics and forest structure. In this paper we focus on forest structure aspects and report about an approach for mapping two them atic classes-the swamp forest and lowland rain forest-by radar remote sensi ng at regional scale and high spatial resolution. The proposed solution hin ges on the recent availability of a large radar mosaic acquired over Centra l Africa wall-to-wall by the Synthetic Aperture Radar instrument on board t he ESA ERS-1 satellite. The focal points and main issues of this study are: the global mapping approach, using continuous spatial sampling over the re gion of interest; the signal processing techniques; the up-scaling to wide area of local area classification and (more critical) validation techniques . Results achieved so far already show that blanket radar coverage of the t ropics can provide thematic information on the forest composition of a whol e ecosystem at an unprecedented level of detail and accuracy.