Frontiers of Biogeography

Spatially explicit biogeographic models are among the most used methods in conservation biogeography, with correlative species distribution models (SDMs) being the most popular among them. SDMs can identify the potential for species’ and community range shifts under climate change, and thus can inspire, inform, and guide complex and adaptive conservation management planning efforts such as collaborative transboundary conservation frameworks. However, SDMs are rarely developed collaboratively, which would be ideal for conservation applications of such models. Further, SDMs that are applied to conservation often do not follow best practices of the field, which are particularly important for applications in climate change contexts for which model extrapolation into potentially novel climates is necessary. Thus, while there is substantial promise, particularly among machine-learning based SDM approaches, there are also many pitfalls to consider when applying SDMs to conservation, and especially in the context of transboundary management under climate change. Here, we summarize these pitfalls and the key steps to mitigate them and maximize the promise of applying SDMs to facilitate transboundary conservation planning under climate change. We argue that conservation modeling capacity must be elevated among practitioners such that they can easily implement best practices when using SDMs, especially regarding: 1) avoiding model overcomplexity, 2) addressing input data bias, and 3) accounting for uncertainty in model extrapolations and projections. While our discussion centers mainly on the pitfalls and opportunities of applying the most popular correlative SDM algorithm, Maxent, our suggestions can also be generalized to a range of other SDM tools. Overall, improved training in, tools for, and implementation of best practices in biogeographic models such as SDMs hold great promise to facilitate and help guide complex, transboundary collaborations for long-term planning of conservation under climate change.

Tortoises and freshwater turtles are among the most threatened taxa of vertebrates in the world due to consumption, urban development, agriculture, and land and water pollution. About 50% of the currently recognised chelonian species are considered threatened with extinction according to the IUCN Red List. Asia is an epicentre for the turtle and tortoise extinction crisis, containing the highest diversity of threatened species. In this study, we used species distribution models (SDMs) to assess the effectiveness of existing protected areas across Southeast and South Asia for the conservation of three large critically endangered freshwater turtles (Batagur borneoensis, B. affinis, and Pelochelys cantorii). We derived the models based on selected bioclimatic variables at the sites of known species records. Our SDMs showed that Indonesia is of particular importance in prioritising conservation for these three species, containing the largest areas of suitable habitat within protected areas. However, when considering water surface coverage, Thailand has the highest proportion of suitable areas under protection. Our results suggest that the present cover of protected network reserves seems inadequate in terms of size and should be expanded to sustain populations of the three target species. Therefore, we identified priority areas and reserves critical for further field surveys to guide the potential discovery of novel populations. To investigate the effect of climate change, we also projected potential distributions onto ensembles of four IPCC story lines. As a result, we found larger extralimital areas of suitable environment for all three species, particularly northwards and inland. However, high degrees of uncertainty in climate conditions indicate few reserves may provide long term protection. Lastly, we review the threats and propose recommendations for conservation of these poorly known freshwater turtles.

Climate change has potential effects on global biodiversity by shifting the optimal distribution of terrestrial organisms, particularly species with narrow distributions. Goniurosaurus lichtenfelderi, a forest-dwelling lizard, is found on both the islands and mainland of northern Vietnam and southern China. The species is categorized as Vulnerable in the IUCN Red List and was recently listed in CITES Appendix II and the Vietnam Government’s Decree 06 in 2019 due to severe anthropogenic impacts on its populations. In this study, we employ Maxent species distribution modeling with climatic and vegetation cover data to identify the potential distribution of G. lichtenfelderi. We also used this approach to assess future climate impacts on the potential distribution under different climate change scenarios. Our model predicts that the potential distribution of G. lichtenfelderi will shrink significantly under future scenarios and even vanish in the entire study area under novel environmental conditions of the BCC-CSM 1-1 – RCP 8.5 scenario by the 2070s. Overall, the current potential distribution is expected to shift towards higher latitudes within the next decades. The forecasted maps provide useful guidelines to implement conservation strategies to mitigate synergistic impacts from climate change and other negative anthropogenic activities. In the context of the potentially severe impacts, the border areas between China and Vietnam, Yen Tu Mountain Range, Bai Tu Long National Park, and their surroundings should be considered core refugia for the species, where conservation measures need to be prioritized in the future.

The Sino-Vietnamese border region is known for having unique and high levels of biodiversity. Global climate change is expected to alter the region’s climate and related changes in habitats and ecosystems will result in shifts in species’ distributions and increase the likelihood of local and global extinctions. Ecological Niche Models (ENMs) are widely used to predict the magnitude of potential species distribution shifts in response to climate change and inform conservation planning. Here, we present climate-based ENM projections of future climatically suitable habitat for the Daguo Mulian tree (Magnolia grandis), a critically endangered species of high ecological and cultural value in the Sino-Vietnamese border region. Projections of modeled climatically suitable habitat for M. grandis, both for the 2050s and 2070s, suggest significant habitat loss within conservation areas, and a defining shift in the location of suitable habitat. Future projections are conservative and do not account for dispersal limitations or species interactions or other factors, and thus may overestimate potential shifts and underestimate losses. Our results suggest that current conservation management efforts for M. grandis, which include community forest conservation monitoring combined with nursery cultivation efforts, can continue to have success if implemented in an adaptive management framework with long-term research and monitoring to inform forward-thinking decisions with future climatic suitability in mind. The results also underline how endangered species’ distributions may shift across borders as they track suitable climates, emphasizing that nations will need to cooperate to effectively manage threatened species and habitats and prevent extinctions.

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 climate-only 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 of suitable habitat in existing conservation areas. This study shows the importance of considering other abiotic factors beyond climate in projections of suitable habitat under climate change for species in complex landscapes. Because our results show that karst and climate interact to explain the distribution of a karst-adapted species, the results also suggest that, under climate change, these interactions are likely to produce altered networks of species into novel biological communities. Finally, our results support the need for conservation of limestone habitats and cross-border collaboration to maintain refuges and movement connectivity for endangered species in the face of climate change.

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 agencies, research institutions, and non-governmental conservation organizations will play an important role in conserving the remaining habitat of this endangered species.

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 km² in 2041 – 2060 period and about -25,000 km² in 2061 – 2080 period, compared to the current predicted range, but they also predicted the currently occupied Trung Khanh-Jingxi Forest as suitable across all future scenarios. Thus, some of the predicted climatically suitable areas that are close to the current known range may be worth targeting for future habitat restoration and population re-establishment and recovery efforts, while balancing other threats and management concerns.

The endangered crocodile lizard, Shinisaurus crocodilurus, is seriously imperiled by anthropogenic threats, including habitat loss and degradation and most critically over-collection for the international pet trade. As a result, population sizes of crocodile lizards have sharply declined throughout their range, with only a small number remaining in China and a handful of individuals left in Vietnam. To prioritize conservation measures for the species, in this study, we generate new mitochondrial sequences of important new samples and analyze them with existing data. Our results confirm a new genetically distinct population in China, highlighting cryptic genetic diversity within the species. The assessment of climate change impacts on the species suggests that the suitable habitat of one population in China will become severely fragmented, decreased in size, and shifted, while the habitat of two other Chinese populations will remain stable and may even expand given future climate scenarios. In Vietnam, Yen Tu Mountain Range is predicted to serve as a refuge in different climate change projections, but suitable habitat in the border area between Vietnam and China will likely shift geographically. Based on our results, we recommend further field surveys to locate the natural distribution range of the newly identified molecular clade in China and determine the distribution extension of the Vietnamese population in the border area, especially potential occurrence on the Chinese side. Considering the impacts of climate change on the Vietnamese population, designing a corridor to connect the subpopulation’s habitat in the border area with nature reserves in Yen Tu Mountain Range and/or translocating lizards from the site to more suitable habitats might help secure the subpopulation in the context of climate change. In all recommended conservation measures, close collaboration between Vietnam and China will be crucial to effectively protect this potentially shared subpopulation of the highly threatened species.