Cumulative disturbances to assess forest degradation using spectral unmixing in the northeastern Amazon

International audienceQuestion: Tropical forests are subject to disturbances by logging, gathering of fuelwood,and fires. Can degradation trajectories (i.e. cumulative disturbances eventsover a period of timer) be identified using remote‐sensing Landsat time series?Location: Paragominas (Pará, Brazil), a municipality covering 19,395 km² in the northeasternAmazon.Methods: We used Landsat annual imagery from 2000 to 2015 and spectral mixtureanalysis to derive time series of the fraction of soil (S), active photosynthetic vegetation(PV), and non‐photosynthetic vegetation (senescent) (NPV) indicators.Results: The NPV values over a 16‐year period revealed five different degradationtrajectories (i.e., cumulative disturbances in space and over time): undisturbed forest,selectively logged forest (with a management plan), overlogged forest (no managementplan), overlogged forest (charcoal production) and burned forest. The varianceof NPV calculated per pixel over the same period is useful to map forest degradationover Paragominas municipality, highlighting the role of disturbance factors (logging,fuelwood gathering and fire).Conclusions: The fractional cover of NPV obtained from spectral mixture analysiscan be used to differentiate degradation trajectories and to map forest degradation