Assessment of climate change impacts on one of the rarest apes on Earth, the Cao Vit Gibbon Nomascus nasutus

The Cao Vit Gibbon ( Nomascus nasutus) is a critically endangered species of gibbon that was historically wideranging 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 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 reestablishment and recovery efforts, while balancing other threats and management concerns.