Spatiotemporal Dynamics of Buddleja officinalis Maxim. Habitat Suitability Under Climate Change in China

The geographical distribution of plant species is being fundamentally altered by ongoing global climate change. B. officinalis, an important medicinal and nectar plant native to South China, may experience uncertain alterations in its suitable habitat under projected climatic changes. To predict where B. officinalis may find suitable environments across China, this work drew upon 346 presence records alongside 24 predictor layers (climatic, topographic, vegetative, and anthropogenic) and employed an ENMeval-tuned MaxEnt framework. Habitat suitability was projected for the present day and three future time slices (2050s, 2070s, 2090s) under four Shared Socioeconomic Pathways (SSP126–SSP585). The main results are as follows. (1) Bio7 (temperature annual range), altitude, and Bio12 (annual precipitation) proved to be the three most influential predictors, with a combined relative importance exceeding 91%. Their optimal ranges were 16.05–29.88 °C for Bio7, 6.53–2513.17 m for altitude, and below approximately 1800 mm for Bio12, indicating a preference for subtropical mountain habitats with moderate seasonal temperature variation and well-drained conditions. (2) The present-day high-suitability zones lie predominantly within three provincial-level regions (Yunnan, Guizhou, and Sichuan) plus parts of southern Gansu and southeastern Fujian, spanning 61.16 × 104 km2. (3) Future projections reveal a clear emission-dependent divergence. Under the low-emission pathway (SSP126), suitable habitat fluctuates but partially recovers by the 2090s. Under the most extreme pathway (SSP585), suitable habitat shows persistent contraction, with the high-suitability extent declining to 7.91 × 104 km2 by the 2050s, a reduction of 87.07% relative to the present day, while the distributional core shifts more than 200 km northwestward. Across all scenarios, the centroid consistently migrates northwestward, though distances vary from 38.47 km (SSP245) to over 200 km (SSP585). Conservation priority should be given to retention zones in Yunnan, Guizhou, and Sichuan, whereas potential expansion areas in Shaanxi, Henan, and Shandong warrant close surveillance. These findings provide a quantitative basis for cultivation regionalization, wild resource conservation, and climate-adaptation strategies for B. officinalis.