Climate change does not always restrict the distribution of species: insights from ensemble distribution modelling

Climate change is rapidly altering species distributions, posing a significant threat to endemic and medicinally important plants with narrow ecological niches. We hypothesize that future climate scenarios will substantially reduce the suitable habitat of Bistorta amplexicaulis across the Himalayan biodiversity hotspot. Given its medicinal significance, limited distribution, and susceptibility to climate variability and anthropogenic pressures such as overharvesting and grazing, Bistorta amplexicaulis serves as an ideal candidate to evaluate how multiple stressors may reshape species distributions under future climate scenarios. To test this, we employed an ensemble species distribution modelling (SDM) approach integrating multiple algorithms and climate datasets at global and regional scales. Our results indicate that the current distribution of B. amplexicaulis is primarily concentrated in the Western Himalaya, including Jammu and Kashmir, Himachal Pradesh, Uttarakhand, northern Pakistan, and northwestern Nepal, with temperature seasonality (BIO4) and precipitation seasonality (BIO15) emerging as the most influential predictors. Future projections reveal a pronounced contraction in suitable habitats, with losses ranging from 40.29% under RCP4.5 (2050) to 83.42% under RCP8.5 (2070), particularly across the western Himalayan region. However, localized habitat gains are predicted in areas such as northern Uttarakhand. Overall, our findings demonstrate a strong climate-driven redistribution of B. amplexicaulis, highlighting temperature as a critical determinant of its ecological niche. These results underscore the urgency of incorporating climate projections into conservation planning for medicinal plant species in the Himalaya.