Ecological niche models (ENMs) can project changes in species' distributions under climate change and thus inform conservation efforts and further our understanding of patterns of change.Predictions of species' distribution shifts under climate change in topographically and geologically complex landscapes, such as karst landforms, should be improved by better integration of non-climate abiotic variables, such as karst geology or habitat structure, into model projections. We built ENMs for one of the limestone langurs, a group of leaf monkeys adapted to forests on the Sino-Vietnamese limestone karst landform. We collected occurrence localities for François' leaf monkeys (Trachypithecus francoisi) and thinned them to avoid sampling bias. We included as environmental parameters a global dataset for karst geology and 19 bioclimatic variables derived from monthly temperature and precipitation at 30 arc-second resolution. ENMs including karst geology and climatic variables outperformed and differed spatially from climateonly models. Across six future-climate scenario projections, the optimal karst+climate model differed from the best climate-only model and predicted more spatial overlap with karst in the future, a contraction in total area of suitable habitat by the 2070s, and a small loss in the amount Highlights• Climate change may result in shifts in species' distributions, leading to changes in biological communities and increasing the likelihood of local and global extinctions.• High endemic biodiversity coincides with known and unknown biogeomorphological feedbacks and interactions in topographically and geologically complex landscapes like karst landforms, which can complicate predictions of species' distribution shifts under climate change.• We built and projected distribution models for Trachypithecus francoisi, a leaf monkey adapted to forests on the Sino-Vietnamese limestone karst landform, to show that models combining karst geology and climate as drivers outperformed models built only with climate data, with differing projections for distribution shifts under future climate change.• Including karst geology or other non-climate abiotic variables that approximate microclimate heterogeneity will be important for distribution shift predictions for other species in karst landforms and other complex landscapes.• Urgent, cross-border collaborations are likely needed for the conservation of the endangered biodiversity of the Sino-Vietnamese Karst Landform in the face of climate change.

The Cao Vit Gibbon (Nomascus nasutus) is a critically endangered species of gibbon that was historically wide-ranging but is now known to occupy only one forest patch that straddles the China-Vietnam border. While past and current threats to the species include poaching and habitat destruction, the potential effects of global climate change on this species and its current habitat are still poorly known. Species Distribution Modeling (SDM) is often used to predict the risk of potential species distribution shifts in response to climate change and inform conservation planning including restoration and reintroduction efforts. Here, we present optimally tuned SDMs to predict climatically suitable habitat for N. nasutus, projected under a range of future climate change scenarios. Our SDMs showed high predictive performance and successfully predicted the current known range, but also showed expected areas of overprediction to a much wider area that likely reflects the historical distribution of the Cao Vit Gibbon across southern China and northern Vietnam. SDMs that projected across a range of future scenarios estimated an overall loss in total area of climatically suitable habitat, with the average value of about -23,000 km 2 in 2041 -2060 period and about -25,000 km 2 in 2061 -2080 period, compared to Highlights• For species with a very small population such as the critically endangered Cao Vit Gibbon, climate change presents a potentially severe threat to its long-term conservation in synergy with other direct threats such as habitat loss and poaching.• Planning for habitat restoration and population re-establishment efforts for critically endangered species should take into consideration future climatic suitability.• Cross-border partnerships are essential for conservation management of critically endangered species under climate change.• Species distribution models for the critically endangered Cao Vit Gibbon suggest its current occupied area will remain climatically suitable into the future, and while the total area of climatically suitable habitat in the future is highly likely to decrease overall, we reveal potential sites for habitat restoration and population re-establishment.

The Southern Yellow-cheeked Gibbon (Nomascus gabriellae) is an endangered species found only in a small region of Indochina, and its populations have declined in most known sites. In this study, we use Maxent, a robust and widely used species distribution modeling approach, to predict the current and future distributions of the Southern Yellow-cheeked Gibbon over its entire range based on an extensive review of published records. In total, we compile and provide a comprehensive set of known distribution records of the species from Cambodia, Laos, and Vietnam. The model results show that N. gabriellae potentially occurs in much of area around the Central Highlands in both Vietnam and Cambodia sides and the southern end of Laos. Our study suggests that protected areas in this region will play a key role in conservation actions for the gibbons. In addition, the distribution of the gibbon in future climate conditions, even in the best-case scenario, is likely to shrink significantly, as the species would have to move upwards to higher elevations. Under such impact, the populations will become more fragmented and restricted to a few areas with higher elevations. Our study also confirms that the climatic difference in distribution ranges may not be fully responsible for the speciation and biogeography of the N. annamensis/gabriellae complex.

Indochina is known as one of the world's biodiversity hotspots, with populations of many endangered and/or endemic species dramatically declining due to a range of threats, such as illegal hunting, habitat destruction, and global climate change. Climate change is expected to alter the region's habitat and ecosystem conditions, force contraction of species ranges, and increase the likelihood of local extinctions. Maxent is a widely used modelling approach to predict the species' current potential distribution, project range shifts in response to climate change, and inform conservation planning. Here, we collated known records and built models for both present and future climatically suitable habitat of the Owston's Civet (Chrotogale owstoni), an endangered and poorly studied small carnivore occurring in Vietnam, eastern Laos, and a small part of southern China. Projections of climatically suitable habitat for the civet in most climate change scenarios and timeframes suggest significant habitat loss and fragmentation within its current range as a consequence of upward contraction. We recommend that future conservation efforts for C. owstoni focus on key refugia spreading along the Annamite Range in the border area between Vietnam and Laos. To mitigate climate-related extinction risk, close cooperation between Vietnam and Laos' governmental 3 agencies, research institutions, and non-governmental conservation organizations will play an important role in conserving the remaining habitat of this endangered species. Highlights• Terrestrial mammals have already been negatively affected by climate change at the global scale. However, the threat has not been evaluated for most species in Vietnam and neighbouring countries. • This study assesses the impacts of climate change on the endangered Owston's Civet by modelling its distribution under various climate change scenarios. Our results reveal significant habitat loss and fragmentation across the species distribution range, as it moves up to higher elevations in response to a warming climate. • Remarkably, the number of protected areas with climatically suitable habitat for the species are projected to decline from 21 currently (3 in Laos and 18 in Vietnam) to 13 (3 in Laos, 10 in Vietnam) in future climate change scenarios. • To better protect the species from this threat, future conservation efforts should focus on climatically stable areas situated along the border between Vietnam and Laos. Effective conservation measures to secure the climate refugia and reduce the current level of poaching and habitat loss would therefore require close cooperation between Vietnam and Laos.

The Red-shanked Douc (Pygathrix nemaeus) is the only douc species recorded in all three countries of Indochina. It is classified as Endangered by IUCN, and is believed to have experienced a major drop of more than 50% of its population over the last 40 years. The known distribution of main P. nemaeus populations in Vietnam ranges from Pu Mat National Park, Nghe An Province in the North to the Kon Ha Nung, Gia Lai Province in the South. In this study, we used Maxent, a species distribution modeling approach that is shown to a have high predictive power even with low number of occurrence records, to predict the current distribution of the Red-shanked Douc in Vietnam based on published records. The results show that P. nemaeus inhabits a region from Nghe An to Kon Tum Province, with areas from Ha Tinh, Quang Binh, Quang Tri, Thua Thien -Hue, Da Nang -Quang Nam Provinces exhibiting the highest potential. With all model parameters already listed here, studies in the future may incorporate more occurrence records to develop better models, or other environmental variables to assess the influence of different factors on the species distribution. The results also suggest that species distribution modeling, coupled with a carefully checked and filtered occurrence dataset, as well as species-specific model fine-tuning and evaluating, can help address many conservation issues in Vietnam.