Comparison of optical and SAR data for forest cover mapping: REDD+ may be helped by SAR data

For Reduced Emissions from Deforestation and forest Degradation (REDD+) purposes, the standard method consists in using optical data to assess change in forest cover. However, SAR data are sensitive to forest above-ground biomass; thus an adequate SAR system, with long wavelength, could provide mapping of biomass and its change over time to be used for estimating carbon emissions. In this paper, the focus is on the comparison of forest cover maps derived from optical data and from SAR data in the Centre Province of Cameroon (about 84 000 km²), which contains humid tropical forests and woody savannas. The forest-non forest maps from optical and SAR data have comparable validation results. However, SAR-based methods are easy to implement, do not require extensive reference samples for calibration, and answer to the key question for carbon cycles studies which is how much biomass or carbon has been disturbed.