Vulnerability assessment of Taxus wallichiana in the Indian Himalayan Region to future climate change using species niche models and global climate models under future climate scenarios

Climate change is a major threat to biodiversity as many species are facing the risk of extinction due to their inability to adapt to the changes in temperature, precipitation, and other environmental variables. The impact of climate change on the habitat distribution of Taxus wallichiana, a medicinally important endangered tree species, has not been studied specifically for the Indian Himalayan region (IHR). We assessed the vulnerability of the species to climate change using Ecological Niche Modeling (ENM) in conjunction with two latest global climate models (GCMs) viz., HadGEM3-GC31-LL and IPSL-CM6A-LR, under two future scenarios i.e. Shared Socioeconomic Pathways (SSPs) - SSP126 and SSP585 from Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, 2023. Based on current distribution of the species and bioclimatic conditions., the Maxent-derived projections indicated significant reduction in its suitable habitat in IHR. Under the moderate scenario i.e. SSP126, suitable habitats are expected to decrease to 6,313,494 ha (10.62% of the total geographical area of IHR) with HadGEM3-GC31-LL and to 4,161,437 ha (7.00%) with IPSL-CM6A-LR from the present distribution area of 8,132,637 ha (13.68%). Under high-emission SSP585 scenario, the predicted habitat area is expected to decline to 4,833,212 ha (8.13%) with HadGEM3-GC31-LL and to 3,204,306 ha (5.39%) with IPSL-CM6A-LR.Annual mean temperature, isothermality, and annual precipitation were important environmental variables impacting the species distribution and models’ predictive capacity. The model outputs clearly predict a gloomy picture under both the future climate scenarios for T. wallichiana emphasizing the need for a targeted conservation effort for the species. .