Detecting Pollution Damage to Forests in the Kola Peninsula Using the ERS SAR

We demonstrate the potential of the C-band Vertically polarised transmission, vertically-polarised reception (VV) polarized European Remote-Sensing Satellite (ERS) Synthetic Aperture Radar (SAR) to provide a capability for forest mapping with particular regard to forest degradation caused by pollution near the Severonikel smelter in the Kola Peninsula, Northern Russia. ERS SAR images covering the period from summer 1993 to summer 1995 are analyzed, and it is shown that a combination of acquisitions from summer and winter reveals areas of forest destruction, driven mainly by the summer (May) acquisition. The damaged forest is approximately the same brightness as undamaged forest in the winter but is found to be approximately 3 dB brighter in the summer. Regions of forest that have been damaged by wildfire are indistinguishable from the pollution-damaged areas. The physical basis for these observations is highlighted using a combination of knowledge of the in situ conditions and theoretical modeling. Destruction of the vegetation canopy (associated with pollution or fire) makes the radar measurements sensitive to the state of the underlying ground. During early summer (the principal time of snowmelt) a rough and wet snow surface causes an increase in backscattering coefficient in areas where the forest canopy has been destroyed. The modeling is also extended to alternative polarizations to study the potential of future Synthetic Aperture Radars, such as the Advanced SAR to be carried on board Envisat, and other systems to enhance this mapping capability.