The Effects of Climate Change on the Future Distribution of Astragalus adscendens in Central Zagros, Iran

Iran is one of the principal centers of Astragalus genus. Astragalus adscendens is a valuable endemic plant. There is less information about the effect of climate change on Astragalus genus especially A. adscendens. In this study, we used the ensemble modeling based on seven species distribution models to predict the spatial distribution of A. adscendens. The presence of A. adscendens points was recorded from our field surveys in Chaharmahal-va-Bakhtiari province as a semi-arid part of Central Zagros, Iran between 2015 and 2016. The future projections were made for the year 2050 and 2070 with two Representative Concentration Pathways (RCPs) scenarios (4.5 and 8.5). Also, in this approach, species occurrence data (140 points), 19 bioclimatic predictors from HadGEM2-CC (Hadley Centre Global Environmental Model, version two - Carbon Cycle), MRI-CGCM3 (Meteorological Research Institute Coupled Global Climate Model Version three) and three physiographic variables were used. According to the ensemble model, 33.58% of the study area (548678 ha) was suitable for the A. adscendens. This research showed annual precipitation, isothermality, temperature annual range and slope have played the most important role in habitat suitability of this species. The response curves showed that occurrence probability of A. adscendens mostly exists in habitats with annual precipitation from 380 mm to 630 mm, isothermality from 35.7 to 36.8 (dimensionless), temperature annual range from 40.5 to 43°C and slope of 0.1 to 30 degree. The decline of suitable habitats will be 59.3% to 89.7% by 2050 and 2070. In contrast, 18.1% to 56.2% of currently unsuitable habitats can become suitable with climate changes. Evaluations showed that Random Forest was found to be the most reliable model for species prediction. Predicting the potential future changes in suitable habitat for A. adscendens will allow more reliable planning and management of this valuable species for experts.