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

Hoang Trinh-Dinh,Nhung Thi Hong Cao,Minh Duc Le,Xingkang Li,Mary E Blair,Anh Tuan Nguyen

doi:10.21425/f5fbg53320

Abstract

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.

Highlights

Nomascus is the second-most species rich genus of gibbons with a total of seven species, of which six occur in Vietnam (Rawson et al 2011)
Trung Khanh Cao Vit Gibbon Conservation Area was established in Vietnam in 2007, and Bangliang Nature Reserve was established in China in 2009 to conserve this population
There was no concrete population data for the species before the 2000s, given the scale of poaching and habitat destruction in both China and Vietnam for the last 60 years (Sterling et al 2006, Liu et al 2019), many presumed that the Cao Vit Gibbon populations had declined and were extirpated at most sites (Rawson et al 2011), resulting in its listing as critically endangered in the IUCN Red List (Rawson et al 2020)

Summary

Introduction

Nomascus is the second-most species rich genus of gibbons with a total of seven species, of which six occur in Vietnam (Rawson et al 2011). All six gibbon species in Vietnam are severely threatened by illegal hunting and habitat destruction, and are listed either as Endangered, or Critically Endangered in the IUCN Red List (Rawson et al 2020). There was no concrete population data for the species before the 2000s, given the scale of poaching and habitat destruction in both China and Vietnam for the last 60 years (Sterling et al 2006, Liu et al 2019), many presumed that the Cao Vit Gibbon populations had declined and were extirpated at most sites (Rawson et al 2011), resulting in its listing as critically endangered in the IUCN Red List (Rawson et al 2020). The species is restricted to the same forest patch straddling the Chinese - Vietnamese border where it was initially rediscovered, which comprises a total of 2,500 ha of limestone forests

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