In Algeria, the mountainous zones represent 11% of agricultural land of the country and are home to 25% of the population. The economic development and the associated urbanization have led to environmental degradation in the Traras Mountains, which are part of the Atlas Mountains. With the aim to evaluate the degradation consequences of this region, we focused on the evolution of land use and land cover over 36 years (1984–2020). Accordingly, we used Landsat and Google Earth Pro images, topographic and ecological inventory maps, as well terrain truth; our analysis tools were mainly based on ArcGIS, Global Mapper, and ENVI software. The diachronic analysis showed that the Traras Mountains lost 8,100 ha of agricultural and forestland between 1984 and 2020. Relating to this, we point out the destruction of 9,200 ha of forested area by the fire. The urbanization also contributed to the loss of agricultural and forested areas (6,300 ha), of which 27% are located in the coastal zone. The built-up situation led to an increase of soil impermeability which causes flooding during heavy rainfall.