Forest monitoring is a major concern today due to climate changes, conservation of fauna and flora and to the lack of water. Therefore, several environmental monitoring techniques have been developed and used to detect changes in the scenes. The use of SAR (synthetic aperture radar) is appropriate to detect forest changes due to its independence of atmospheric and lighting conditions. However, currently, also SAR change detection has been faced limitations due to human ilegal activities under the forest. In this case, P-band SAR images can be a great tool, because of its capacity to pass through vegetation. This paper will present a new method of change detection by multitemporal full-polarimetric P-band SAR imagery using Pauli Decomposition to separate artificial objects and, therefore, detect targets that appeared and disappeared under the canopy. Experimental tests have been performed using real SAR data acquired by the airborne sensor OrbiSAR-2 from Bradar and hidden targets (cars) in the Brazilian Atlantic Forest (Tropical Rain Forest). The first obtained results were good and show that idea can be useful for a variety of surveillance applications even search and rescue. A short analysis of the relationship between the position of vehicles and their detection was also performed.