Predicting the Potential Climatic Suitability of Typical Poisonous Weeds on the Qinghai–Tibet Plateau Under Climate Change Using Biomod2 and a Single Global Climate Model

The expansion of poisonous weeds on the Qinghai–Tibet Plateau (QTP) poses increasing challenges to alpine grassland ecosystems and livestock production. Using the Biomod2 ensemble modelling framework, we assessed the current and future potential climatic suitability for five poisonous weed species—Stellera chamaejasme, Thermopsis lanceolata, Gymnaconitum gymnandrum, Oxytropis kansuensis, and Ligularia virgaurea—using climatic and topographic predictors, with future projections based on the single global climate model BCC-CSM2-MR under SSP1–2.6, SSP3–7.0, and SSP5–8.5. Precipitation of the warmest quarter (Bio18) and mean temperature of the wettest quarter (Bio8) showed the highest average variable importance across species, although their contributions varied among model realizations. Under current climatic conditions, suitable habitats were concentrated mainly in the eastern and southeastern QTP, with G. gymnandrum occupying the largest total and highly suitable areas. Under the BCC-CSM2-MR projections, total suitable habitat increased for all five species across the three SSPs, although the magnitude and spatial pattern of change varied among species, suitability classes, scenarios, and periods. T. lanceolata showed the greatest relative increase in suitable habitat, whereas the highly suitable habitat of O. kansuensis declined by approximately 94% under SSP5–8.5 in both future periods despite an increase in its total suitable area. These findings provide a basis for ecological risk assessment, targeted monitoring, and adaptive grassland management under future climate change.