Modeling the potential distribution areas of castanea sativa mill. within the boundaries of the bolu regional directorate of forestry based on climate variables

This study aims to assess the potential impacts of climate change on habitat suitability of Castanea sativa (chestnut) species in Bolu Regional Directorate of Forestry in northwestern Turkey. The MaxEnt algorithm was used for species distribution modeling, based on the Medium Pathway (SSP2-4.5) and High Emission (SSP5-8.5) scenarios for the years 2050, 2070 and 2090. Bioclimatic and topographic environmental variables were selected based on correlation analysis and ecological significance criteria to minimize multicollinearity. The accuracy assessment of the model showed a high performance with AUC (Area Under Curve) values of 0.961 for training data and 0.959 for test data. The model outputs reveal that the most determinant environmental variable on Castanea sativa distribution is the precipitation of the driest quarter (Bio17) with a contribution of 42.2%, followed by rainfall seasonality (Bio15, 27.6%) and temperature seasonality (Bio4, 15.7%). According to the SSP5-8.5 scenario, unsuitable areas for the species are projected to increase from 907,585.92 hectares to 910,104.16 hectares by 2050, 911,058.07 hectares by 2070 and 909,943.00 hectares by 2090. High suitability habitats, on the other hand, have followed a relatively stable course, decreasing from 310.92 hectares to 266.47 hectares. On the other hand, under the SSP2-4.5 scenario, there will be a more significant shrinkage in high suitability areas and these areas are projected to decrease to 133.26 hectares by 2090. Under this scenario, the extent of unsuitable areas reaches 912,802.41 hectares, while habitats of medium suitability increase from 34,584.00 to 36,261.46 hectares, indicating the importance of transition zones. In terms of elevation distribution, Castanea sativa individuals are mostly found at altitudes below 1000 meters, and 20.2% of the available suitable habitats are located between 0-100 meters. Under future scenarios, it is predicted that the species will spread to lower altitudes and especially under the SSP5-8.5 scenario, high suitability areas will be concentrated at lower elevations. The findings reveal that the development of climate change compatible forestry practices and effective conservation strategies are critical for the sustainability of species with similar ecological requirements, especially Castanea sativa species.