Climate is critical in determining habitat distribution and affects ecosystem function and composition. Climate change is attributed to anthropogenic activities altering an organism’s adaptability and shifting patterns (Chen et al. 2011). The earth's surface's mean average temperature has risen by approx. 0.85°C over the last three decades (IPCC, 2014). It is projected that the mean global surface temperature will increase by 0.3–4.8°C by the end of the 21st century. Climate change may significantly influence diverse ecological phenomena such as structure, function, and composition, including habitat distribution and range shift resulting in biodiversity change. The Indian Himalayan Ecosystem (IHE) is very sensitive and vulnerable to climate change and its associated variables (IPCC, 2007). The biological organism combats climate change and its associated impacts in several ways. They make efforts to survive in the environment by developing adaptations to novel environmental conditions and shifting their habitat to suitable environmental conditions. They face extinction if organisms are unable to move or develop adaptation mechanisms. The species' survival frequency is considerable, aligning with the climate throughout their range in the specific environment. Nevertheless, conserving this ecological balance in climate change would require continuous monitoring to trace the shift in the ecological system.
The Indian Himalayan Ecosystem (IHE) is very sensitive and vulnerable to climate change and its associated variables (IPCC, 2007). In the IHE, an abnormal temperature and precipitation pattern will become more extreme. Potential climate change impacts on biodiversity include habitat loss, variations in phenotypic expression, alien species invasions, habitat shifting towards the higher elevation, reduction in population and diversity, etc. (Bellard et al. 2012). These consequences could drive habitat loss of threatened species beyond the edge of extinction. Therefore, it is urgent to understand the potential impacts of climate change on the habitat distribution of range-restricted and endangered species in IHE, which is experiencing climate change impacts faster than other ecosystems, to conserve and protect biological diversity (Singh et al. 2010; Singh et al. 2020).
Habitat suitability modelling is the most commonly adopted approach to predict climate change impacts on the species distribution for formulating strategies for conserving and managing biodiversity. This approach provides ways of understanding species responses to climate change and inferring related species predicted distributions over regions, therefore allowing adaptive and effective diversity conservation and management strategies to be adequately applied (Dawson et al., 2011). Predictions of climate change impacts on species distributions are made by integrating various factors such as bioclimatic, physiographic, land use, types, etc. (Wiens et al., 2010). Limited studies are available in the IHE, which focus on the effects of climate change on the suitable habitat distribution and habitat shift of the avifaunal species (Galbreath et al., 2009).
The ensemble modelling approach provides an accurate and more reliable prediction of species distribution or habitats under the influence of climate change (Araujo and New, 2007). If various models are combined using plurality methods (including the mean of all the models), these can form a more accurate projection that outperforms single models (Grenouillet et al., 2011). Spatial and temporal predictions of species distribution models are exceptionally well suited for ensemble modelling and consensus projections. The study demonstrated that single models have an optimal outcome on existing data (Singh et al., 2020). Still, it is not necessary to provide the most reliable results for future predictions, while consensus projections can provide more effective results in the current and future climatic scenarios (Latif et al., 2013; Ahmad et al., 2020). The present study sought to fulfill this gap by using an ensemble modelling approach to understand the climate change impacts on the future habitat suitability of the Himalayan cheer pheasant (Catreus wallichii), a range-restricted species in the Indian Himalayan Ecosystem.
The cheer pheasant (Catreus wallichii) is a range-restricted and vulnerable bird species found in the southern foothills of the western Himalayas, particularly in northern Pakistan, central Nepal, and India at elevations from ~ 1,500 to 2,700 m (Garson et al., 1992; Birdlife International, 2019). The cheer pheasant dwells in the outer hilly range of the Himalayas, which has tall grass and scattered clumps of trees (Singh et al. 2011). Its distribution is patchy due to its specialized habitat requirements and population decline. Climate change may affect cheer pheasant habitat in the coming decades (Inskipp et al. 2016). Cheer pheasant (Catreus wallichii) shift to heights of more than 10,000 feet during summer. Cheer pheasants like beetles, grubs, and snails commonly dig for their food. This species can also consume berries and grass from the ground.
The present study was performed in the Indian Western Himalayas (IWH), consisting of two states (i.e., Himachal Pradesh and Uttarakhand) and one Union Territories (i.e., Jammu and Kashmir) (Fig. 2A). The Himalayan region features four distinct physiographic zones, i.e., Shivalik, Middle Himalayas, Upper Himalayas, and Trans-Himalayas. The Himalayas account for around 80% of the Indian sub-continental total birds (Price et al., 2003). Besides, it is home to the most endangered Asian bird species (Acharya and Vijayan, 2010). The changing climate and increased anthropogenic activities affect the Himalayan biodiversity. Significant latitudinal and altitudinal differences occur in the western Himalayas that manage the surrounding environment. This region has uneven planes with higher altitudinal variations. Besides, various degrees of slope and aspect often control the climate to create several microclimate regions. Alterations in the Himalayan region's precipitation and temperature patterns contribute to significant implications for the threatened species.