Land use/land cover change trends in the Chrea Protected Area of northern Algeria (1984-2021), using Landsat TM+/OLI_TIRS data

Algerian forest landscapes have experienced rapid degradation in recent decades, driven by climatic and anthropogenic factors. Monitoring land use and land cover changes (LULCC) is essential to understanding this process and thus strengthening in situ conservation policies. This study aimed to analyse LULCC trends in the Chrea Protected Area, part of the Central Tellien Atlas, between 1984 and 2021. LULCC was mapped using Landsat TM for 1984 and 2004, and Landsat 8 OLI_TIRS for 2021. The Maximum Likelihood Classification algorithm was used for the supervised classification of LULC into five distinct classes: forest, dense matorral, open matorral, shrub land, and non-vegetated land. A post-classification approach was employed to detect changes over the study period, categorised into four types: deforestation, degradation, reforestation, and recovery. The changes in LULC showed two main trajectories: recovery, then degradation. Vegetation recovery dominated between 1984 and 2004, over an area of 8,560.3 ha (28.21%). This dynamic succession coincided with the area’s rural depopulation, resulting in a decrease in human disturbance on the landscape. In contrast, most vegetation degradation occurred between 2004 and 2021, affecting 5,344.06 ha (17.61%). This degradation primarily resulted from the conversion of forest to dense matorral and may be associated with increased human pressure on forest resources, using fire to expand or renew fodder areas. This degradation has reduced landscape heterogeneity. This study presents the first data on the trajectories of LULCC in the Chrea protected area over 37 years, which will allow for more effective conservation actions for the precarious forest ecosystems of Algeria.