Mapping selective logging in tropical forest with space-borne SAR data

A technique was developed for the mapping of selective logging in tropical forest using PALSAR imagery acquired before and after the logging operations. The technique is based on automatic detection of new forest roads and unsupervised classification of textural features, which were computed from a backscatter ratio image. The technique was adapted for TerraSAR-X and ENVISAT/ASAR data. The accuracy of a PALSAR-based map of selective logging was assessed against reference plot data interpreted from GeoEye-1 imagery. The user's accuracy of selective logging was 95 %. The overall accuracy was 70.4 %. This is affected by the limited size of the area, which was chosen to include a large proportion of selectively logged forest. The accuracy of a TerraSAR-X-based map of selective logging was 53.6 %, but the user's accuracy of selective logging was 100 %. ALOS-type L-band radar data could be applied in an operational system over country-wide datasets to map newly constructed roads. The 40 % underestimation does not make direct reliable mapping of the area of selective logging possible. Instead, L-band derived maps of selectively logged area and new roads can be used in a wider system to pin-point areas of recent logging activity (as a proxy for forest degradation). The detected areas can then be covered by satellite or airborne optical data or ground surveys. The L-band map of areas with logging activity can also be used for stratification for sampling in a statistical area assessment