Population assessment and habitat suitability modelling of endangered medicinal plant, Aconitum heterophyllum Wall. ex Royle in the western Himalaya

Climate change is considered one of the major threats to species extinction. The impact of climate change on the distribution of Aconitum heterophyllum, an endangered species in the northwestern Himalayan state of Himachal Pradesh, remain largely unexplored. In this study, species occurrence data, bioclimatic variables and population distribution data were used to map the current and future distribution (2050 and 2070) of A. heterophyllum. Species Distribution Modelling (SDM) based on Maximum Entropy (MaxEnt) algorithm, driven by climate data from the Global Circulation Model HadGEM3-GC31-LL, statistically downscaled to 1 km spatial resolution, was used for species distribution mapping. Three future scenarios, represented by Shared Socioeconomic Pathways (SSPs)-SSP126, SSP245, and SSP585, were considered. The Bioclimatic variables (Bio 15), which is precipitation seasonality and elevation, were found to positively influence the distribution of A. heterophyllum in the studied locations. Precipitation seasonality ensures adequate water availability in cold and dry habitats, while higher elevations corresponded to high suitablility habitats in the Himalaya. The SDM predicted a total suitable area of 1863.7 km² for A. heterophyllum in Himachal Pradesh. Under SSP126, representing moderate development with minimal environmental degradation, suitable habitat is projected to decrease by 51.28% by 2070. Under SSP245, representing moderate development with more pronounced environmental degradation, suitable habitat is predicted to decrease by 53.64% by 2070. Under SSP585, representing high-emission development with challenges to mitigation, suitable habitat is predicted to decrease by 54.61% by 2070. Overall, the species is expected to lose between 30.68% and 58.51% of its current habitat between 2050 and 2070, posing a significant extinction risk. High-suitability areas were found in the Dhauladhar ranges, alpine regions of Pin Valley National Park, Killar ranges of Chamba, and other areas identified as key for conservation efforts. These regions are crucial for implementing adaptive management strategies to protect A. heterophyllum in the face of global climate change.