Lakes on the Qinghai–Tibetan Plateau (QTP) have experienced significant changes, especially the prevailing lake expansion since 2000 in the endorheic basin. The influence of permafrost thawing on lake expansion is significant but rarely considered in previous studies. In this study, based on Landsat images and permafrost field data, the spatial-temporal area changes of lakes of more than 5 km² in the endorheic basin on the QTP during 2000–2017 is examined and the impact of permafrost degradation on lake expansion is discussed. The main results are that permafrost characteristics and its degradation trend have close relationships with lake changes. Lake expansion in the endorheic basin showed a southwest–northeast transition from shrinking to stable to rapidly expanding, which corresponded well with the permafrost distribution from island-discontinuous to seasonally frozen ground to continuous permafrost. A dramatic lake expansion in continuous permafrost showed significant spatial differences; lakes expanded significantly in northern and eastern continuous permafrost with a higher ground ice content but slightly in southern continuous permafrost with a lower ground ice content. This spatial pattern was mainly attributed to the melting of ground ice in shallow permafrost associated with accelerating permafrost degradation. Whereas, some lakes in the southern zones of island-discontinuous permafrost were shrinking, which was mainly because the extended taliks arising from the intensified permafrost degradation have facilitated surface water and suprapermafrost groundwater discharge to subpermafrost groundwater and thereby drained the lakes. Based on observation and simulated data, the melting of ground ice at shallow depths below the permafrost table accounted for 21.2% of the increase in lake volume from 2000 to 2016.

Climate change has a profound impact on global biodiversity and species geographical distribution, especially in alpine regions. The prediction of species’ habitat could help the understanding of species’ responses to potential climate threats. Triosteum L. (1753) is a typical mountain plant with medicinal and ecological value. There are three species of this genus in East Asia. Triosteum Pinnatifidum Maxim. 1888 and Triosteum himalayanum Wall. 1829 are mainly distributed in the Qinghai–Tibet Plateau and its surroundings, and they are sensitive to climate changes. In this study, a MaxEnt model was used to predict the potential distribution of T. Pinnatifidum and T. himalayanum in the present time and at four different time periods in the future under two different Shared Socioeconomic Pathways (SSPs). Topographic factors were taken into account in the prediction. In the present study, the accuracy of the model’s prediction was verified (the AUC values are 0.975 and 0.974), and the results indicate that temperature is the key factor that affects the distribution of these two species. Compared with current distribution, the potential suitable area of T. Pinnatifidum will increase in the future under two types of SSPs (an average increase is 31%), but the potential suitable area of T. himalayanum will decrease significantly (the average area is 93% of what it was before). In addition, the overlap of potential suitable areas of these two species will also expand, potentially affecting their hybridization and interspecific competition. The centroids of T. Pinnatifidum will migrate to the east, but the trajectory of centroids of T. himalayanum is complex. This study could provide basic data for the resource utilization and biogeography research of Triosteum. It will also be helpful for conservation and sustainable use of mountain herbaceous plants under climate change.