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 Africa, are interesting ecosystems that function as water storage and faunistic and florensis habitat. Moreover, they host a series of bio-chemical processes, such as methane emission, which have a significance in global change issues. Characterization of these complex ecosystems can be tackled from different 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 thematic classes - the swamp forest and lowland rain forest - by radar remote sensing at regional scale and high spatial resolution. The proposed solution hinges on the recent availability of a large radar mosaic acquired over Central Africa wall-to-wall by the Synthetic Aperture Radar instrument on board the ESA ERS-1 satellite. The focal points and main issues of this study are: the global mapping approach, using continuous spatial sampling over the region 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 tropics can provide thematic information on the forest composition of a whole ecosystem at an unprecedented level of detail and accuracy.