ALOS-PALSAR multi-temporal observation for describing land use and forest cover changes in Malaysia

The establishment of plantations in carbon rich peatland of Southeast Asia has shown an increase in the past decade. The need to support development in countries such as Malaysia has been reflected by having a higher rate of conversion of its forested areas to agricultural land use in particular oilpalm plantation. Use of optical data to monitor changes in peatland forests is difficult because of the high cloudiness in tropical region. Synthetic Aperture Radar (SAR) based remote sensing can potentially be used to monitor changes in such forested landscapes. In this study, we have demonstrated the capability of multi-temporal Fine-Beam Dual (FBD) data of Phased Array L-band Synthetic Aperture Radar (PALSAR) to detect forest cover changes in peatland to other landuse such as oilpalm plantation. Here, the backscattering properties of radar were evaluated to estimate changes in the forest cover. Temporal analysis of PALSAR FBD data shows that conversion of peatland forest to oilpalm can be detected by analyzing changes in the value of σoHH and σoHV. This is characterized by a high value of σoHH (-7.89 dB) and σoHV (-12.13 dB) for areas under peat forests. The value of σoHV decreased about 2-4 dB due to the conversion of peatland to a plantation area. There is also an increase in the value of σoHH/σoHV. Changes in σoHV is more prominent to identify the peatland conversion than in the σoHH. The results indicate the potential of PALSAR to estimate peatland forest conversion based on thresholding of σoHV or σoHH/σoHV for monitoring changes in peatland forest. This would improve our understanding of the temporal change and its effect on the peatland forest ecosystem.