R. arboreum’s altitudinal and latitudinal shift in future climate pivots on emission scenarios

Abstract Global warming leads to changes in distribution of species across the globe. Himalayan altitudinal gradients are one of the most susceptible ecosystems to varying climatic drivers and predicting distribution of species on this rugged topography in future climate seeks attention in terms of both ecological and economic importance. Western Himalayan states of Himachal Pradesh and Uttarakhand shelter one-tenth of world’s known higher-altitude plant species. Rhododendron arboreum , the most widely distributed tree in Himalayas, was studied for its distribution in future climate. Ensemble models were employed to predict distribution by 2070 in Representative Concentration Pathways (RCP) 4.5 and RCP 6.0 scenarios. Altitudinal shift was studied by incorporating spatial measures, considering minimum horizontal distance the species can move. Centroidal shift was estimated in terms of both direction and magnitude, and altitudinal analysis was performed at centroidal shift. Results showed that, Himalayan locations in RCP 4.5 scenario would get warmer than RCP 6.0 scenario, and species is just as likely to shift upwards (higher elevations in RCP 4.5 scenario) as downward (lower elevations in RCP 6.0 scenario) despite consistent warming across the study area. Highest suitable elevation range for the species presence is likely to be ~ 2100m in current scenario, 2200m – 2400m in RCP 4.5 scenario, and 1800m – 2100m in RCP 6.0 scenario. Temperate zone of Himalayas may turn out as the most suitable zone for R. arboreum and species is likely to move in Northwest direction with a horizontal distance of 60km and 25km in RCP 4.5 and RCP 6.0 scenarios, respectively.