Biodiversity hotspot assessment in the Altai Mountains transboundary region based on Mammals and Aves

distribution of BHs of TA. The main contributing factors to the distribution of BHs of AA, include: bio11 (21.79%), distoraod (19.52%), waterdistance (11.48%), peo (10.86%). We can see that climate factors are still the key factors that dominate species BHs. BHs for TM, AM, TA and AA are mainly driven by climate, where the climate contributions to TM, AM and TA are 66.95%, 59.65% and 52.04% respectively (sum of climate factors). In addition, the climate contribution of threatened animals is higher than that of non-threatened animals, such as TM>AM, TA>AA. This could mean that the effects of climate change are more severe for spe- cies that already face existential threats. Aves, on the other hand, are more dependent on human activities and landscapes than Mammals, and are especially more dependent on human activities than on other factors. This dependence may lead to more severe impacts of human activities on Aves. Discussion Climate-driven land cover change and biodiversity hotspot distribution mechanism Between the years 2000 and 2020, notable changes in LULC occurred within AMTR. Among these changes, the most prominent was the conversion of approximately 49,262.99 km2 of grass- land to bareland, constituting 38.31% of the total change in area. Subsequently, there was a sig- nificant transformation of approximately 19,611.74 km2 from grassland to forest, accounting for 15.25% of the total change (See S2 for detailed analysis in S1 File). The LEAS module in the PLUS model (see S3 in S1 File) was used to analyze the driving factors of LULCC in AMTR and

each subregion from 2000 to 2020. The results are shown in Fig 5. Over the past 20 years, cli- mate has dominated the overall LULCC (50.87%; we define more than 20% of the second influ- encing factors as dominant). From the perspective of each LULC type, climate has dominated changes in forest (56.26%), grassland (62.31%), bareland (74.43%), and snow/ice (60.38%). Human activities (56.18%) dominate the changes in artificial surfaces, and changes in cropland are mainly caused by human activities (48.08%) and climate (35.04%) playing a joint role. Wet- land changes are mainly driven by climate (52.82%) and topography (40.95%). Water is similar to wetlands, with climate and topography contributing 45.34% and 48.43%, respectively. The dominance of climate as a driving factor for LULCC and biodiversity hotspot distribution suggests that species in the AMTR may face greater challenges due to future climate change. This is because a strong single dominance increases the likelihood of species becoming extinct due to changes in future dominant factors [38]. These findings underscore the need for adaptive man- agement strategies to mitigate the impacts of climate change on biodiversity hotspots. Spatial characteristics of BHs and key environmental factors Understanding the spatial relationship between BHs and key environmental factors can help us more fully understand the distribution of BHs in AMTR. This understanding not only helps reveal species distribution patterns but also provides a scientific basis for ecological manage-

ment and conservation to better protect species diversity [33, 39, 40]. In our study, we analyzed the relationship between species richness and environmental factors in TM, AM, AA, and TA (Fig 6). We observed a significant positive correlation between species richness and elevation, and a clear negative correlation between distance from national borders, water sources, and roads. This means that areas with high species diversity are more likely to be located at high altitudes and close to national boundaries, roads, and water sources. These spatial relationships highlight the influence of topography, human activities, and landscape on biodiversity. Specifically, in terms of distance to water sources, aves are closer to PLOS ONE Biodiversity hotspot assessment in the Altai Mountains transboundary region PLOS ONE | https://doi.org/10.1371/journal.pone.0314075 December 4, 2024 9 / 20