The effect of climate change on the geographical distribution of wild borage in Khorasan Razavi

Climate change which has begun due to human activities in the past centuries, intensified through positive feedbacks as time goes by. Changes in the characteristics of the environment of organisms definitely affect their lives. In the last decade, many studies have focused on the type, size, and extent of this effect on different organisms (including plants) in various ecosystems. In this study, the effect of climate change on the geographical distribution of Anchusa italica in Khorasan Razavi province was investigated at 2080 with RCP 8.5 and under the HadGem2 general circulation model. Despite its medicinal, conservational, economic and even forage importance, this species has never been studied. The impact of climate change on important species can only be examined through modeling, because modeling studies in the natural sciences are the key of many issues that cannot be tracked in normal studies.

At first, field studies were carried out including the record of geographical coordinates of the species presence in the rangelands of Khorasan Razavi province in late spring of 2018 (when the plant was flowering and easily visible and identified) and 113 presence points was recorded for Anchusa italica. Then the 19 bioclimatic variables alongside three topographic variables were used as inputs to GBM model. This model, which is a decision trees based methods, uses numerous incomplete trees to form the final model, and the algorithm required in this study was programmed in the R environment. The model simulates the relationship between the presence of species and climatic and topographical conditions, and then uses this simulation to study the effect of changes in climatic factors on the distribution of species. Two validation indices (AUC and TSS) were used to determine the model's potency.

The maps of suitable areas for wild borage in current climatic conditions and under climate change in 2080 were prepared and the model assessment indices showed that the model has a high ability to predict suitable sites for species presence (AUC = 0.974 and TSS = 0.87). Habitat suitability of this species was highly affected by (BIO1), (BIO2), (BIO15) and (BIO12). Results showed that in comparison with current conditions, about 40% of the climatic suitable area for this species will be diminished with the RCP 8.5 (from the IPCC scenario series). The areas where changes in the habitat of this species occur are displayed in a map.

The effect of climate change on plants is divided into three groups: Adaptation, Shifting and Extinction. According to the results of this study, in the case of wild borage, physiological adaptation is not likely to be possible in the short term (less than few centuries to few millennia). So if this plant fails to alter its distribution range (Shifting or displacement), will have to choose the third way (local extinction or get limited to refuges). Therefore, it is necessary to plan local, national and regional programs to maintain and extend the current habitats of this biological, ecological, medicinal and economic important species and providing access to new habitats for it; alongside the preventive activities of climate change.