Future climate and habitat distribution of Himalayan Musk Deer (Moschus chrysogaster)

Highlights

• MaxEnt predicts ecological niche of a species reasonably well.

• Current modelled and future potential suitable habitat of Himalayan Musk Deer (HMD) was calculated.

• Habitat suitability of HMD differs with different projection scenarios.

• Majority of the current HMD suitable habitat area will remain stable in the future.

• Shift in HMD habitat shows a longitudinal pattern.

Abstract

Change in future climate will either expand, contract or shift the climatic niche of many species and this could lead to shifting of their geographical ranges. Species distribution models identify habitat over a specified area that may have similar ecological characteristics of a species in question. We modelled current and future distribution of endangered Himalayan Musk Deer (Moschus chrysogaster), referred here as HMD, in Nepal Himalaya based on two representative concentration pathways (RCP4.5 and RCP8.5) for the year 2050 and 2070 using MaxEnt and MIROC5 global climate models (GCM). Annual mean temperature, altitude, isothermality and land cover were the major contributing variables to the model with area under ROC (Receiver Operating Characteristic) curve (AUC) being 0.975. Almost 7.7% (11,342 km²) area of the country is currently suitable for HMD. The model shows that a majority of current suitable habitat will remain stable under both RCPs in the future though 29.47% of the current suitability will be decreased by 2070 under RCP4.5, mostly in the western and far western regions. Overall, the shift of habitat shows a longitudinal pattern. Existing protected areas (PAs) account for 52.6% of the total suitable habitat area, and shows variability of changes in suitability under both RCPs in the future. Initiation of trans-boundary conservation programs could offset the likely climate change impact on HMD habitat in Nepal and adjoining native Himalayan ranges.

Introduction

Anthropogenic climate change (CC) has become a major threat to global biodiversity and has affected natural ecosystems in numerous regions around the world. The earth has warmed up by 0.74 °C in the 20th century, and global mean temperatures are projected to increase further by 4.3 ± 0.7 °C by 2100 (IPCC, 2013). Changes in future climate will either expand, contract or shift the climatic niche of many species and this could lead to shifting of their geographical ranges. Of the global 976 species studied, Wiens (2016) found that almost 47% are locally extinct due to range contraction even within current modest temperature rises, and that animals suffered the most (50%) compared to plants (39%). Terrestrial ecosystems have seen widespread changes in its climate in the past (Alley et al., 2003; Diffenbaugh and Field, 2013), and as a result, animal habitat ranges have shifted both in latitude and altitude (Chen et al., 2011; Hickling et al., 2006). Warren et al. (2013) projected that approximately 27% of common and widespread animal species at current time could lose half of their climatic range by 2080.

Around 96% of the Global 200 Ecoregions, identified by World Wildlife Fund (WWF) as priority eco-regions, are likely to experience moderate to pronounced climatic impact by the end of the 21st century (Li et al., 2013). Wildlife, especially mammalian species, in this context could lose substantial amounts of their habitat range at a global scale with future warming climate. Thuiller et al. (2006) projected that 20% of African mammalian species with migration capacity and 40% without migration capacity could fall either within critically endangered or extinct category as a consequences of habitat change by 2080. Likewise, Levinsky et al. (2007) estimated that almost up to 9% of European mammalian species without migration capacity risk extinction while 78% of them risks for severely threatened by 2100. Around 9% of locally found mammals in American continents would likely be unable to keep pace with future climate while 80% could have reduced range size (Schloss et al., 2012).

High species richness and endemism characterizes the Himalayan region due to climate variations, exposure effect and habitat diversity (Aryal et al., 2014; Pandit et al., 2014; Xu et al., 2009). This region however has recently been reported to be warming at a greater rate than the global average, for instance, the global average for the last 100 years was 0.74 °C (IPCC, 2013) while it was 1.5 °C for the Himalayas from 1982 to 2006 (Shrestha et al., 2012). Rapid glacier melt in the Himalaya in recent times is a compelling evidence of such warming (Shrestha and Aryal, 2011). Warming impacts to species, for instance, vegetation range shift and plant composition changes have been documented for western Himalaya (Lamsal et al., 2018; Padma, 2014; Rashid et al., 2015), central Himalaya (Gaire et al., 2014; Chhetri and Cairns, 2015; Lamsal et al., 2017a), eastern Himalaya (Manish et al., 2016; Telwala et al., 2013), southern Tibetan belt (Xiaodan et al., 2011; Zhao et al., 2011) as well as the whole Himalayas and Tibetan Plateau (Lamsal et al., 2017b). Similarly, around 30% of snow leopard (Panthera uncia) habitat is projected to be lost in the whole Himalayan region by 2050, of which 40% could disappear from Nepal alone (Forrest et al., 2012). Aryal et al. (2016) also predicted decreased habitat for snow leopard and blue sheep (Pseudois nayaur) for Nepal with future climate. All these evidences suggest that climatic change drives species to alter their geographic distribution in every region, including the Himalayas.

Himalayan Musk Deer (Moschus chrysogaster) (Fig. 1) is distributed throughout the Himalayan range. In Nepal, two species of HMD are mentioned in the literature, Moschus chrysogaster and M. leucogaster, of which this study concentrates on M. chrysogaster because of the field data availability. HMD has been under the IUCN endangered category since 2008, Appendix I of CITES list and is also protected by the Government of Nepal under the National Park and Wildlife Conservation Act, 1973. HMD is one of the six deer species found in Nepal, and prefers alpine forest habitat of the Himalaya between 2200 and 4300 m. It is native to Nepal, India, Bhutan and China but also reported in Afghanistan, Pakistan and Myanmar (Green, 1986). HMD is solitary and territorial in nature, and is a concentrate feeder with an ability to adapt to poorer diets when high quality food is in short supply (Green, 1987).

The population size of HMD for Nepal and other native regions is unknown. However, it has been decreasing in the last few decades due to anthropogenic activities (such as illegal poaching for musk gland and habitat fragmentation) in China (Yang et al., 2003), India (Syed and Ilyas, 2016), Pakistan (Khan et al., 2006), and Nepal (Aryal et al., 2010; Aryal and Subedi, 2011; Khadka et al., 2017). Such anthropogenic activities, together with ongoing and projected CC, could exacerbate their survival through impacting on their habitat. As stated earlier, many studies have reported habitat shift of species in the Himalaya region. We found no studies on impact of CC on Musk deer and its habitat in Nepal, therefore, this study attempted to investigate (i) current distributional range of HMD (ii) future climate effects on the spatial distribution of HMD, and (iii) climatic variables explaining future spatial distribution of potential habitat of HMD. This study accounted for such distributional change both inside and outside of the protected areas (PAs) of Nepal.