Modeling of the current and future potential distribution of Atlas cedar (Cedrus atlantica) forests revealed shifts in the latitudinal, longitudinal and altitudinal range towards more humid conditions

Environmental forcing affects biodiversity in some parts of the biosphere where many sensitive species, including endemic and rare species, respond through changes in their geographical distribution. Modelling of spatial dynamics of species is crucial to advance our understanding of species' adaptive behaviour and sensitivity to environmental changes and forcings. The present study aimed at assessing suitable habitats of the Atlas cedar (Cedrus atlantica) in North Algeria for the current period (1990-2000) and predicting its future range in 2050 and 2070, following climate warming scenarios. The Maximum Entropy (Max-Ent) model was used to model the present and future potential distribution of Atlas cedar forests. A total of 1328 occurrence records obtained from field surveys and 50 environmental variables were used. These variables included 19 climatic variables (WorldClim database), 21 edaphic proprieties (SoilGrids database), and 10 topographic traits (retrieved from a 30 m digital elevation model). MaxEnt showed high predictive power with a significant value of Area Under Curve (AUC=0.988). Potential distribution of Cedrus atlantica forests for the present period was confined to mountain areas (predicted potential range size = 2089 km(2)). Environmental factors with the highest percentage of contribution included: soil total nitrogen (22.2%), elevation (20.5%), mean temperature of the most humid quarter 'Bio8' (18.8%), slope (12.9%), soil total carbon (10.3%), and precipitation of the driest month 'Bio14' (3.4%). The species range is expected to reduce significantly under future climate change scenarios (decline of about 70.4-80.6% of its current potential distribution), with a shift towards more humid conditions, in this case to the north and east towards more humid climates and mesic habitats. The predicted shifts in the altitude gradient follow in the direction of higher elevations, with the disappearance of cedar forests at low altitudes. This indicates that the identified Atlas cedar refugia resulting from climate change are determined by humidity. Our findings provide information on the magnitude of environmental forcings that seriously threaten Cedrus atlantica forests in drought-prone areas in North Africa. It is therefore necessary to implement effective strategies to preserve and protect more sensitive forests.