The potential impacts of climate change on the distribution of key tree species and Cordyceps in Bhutan: Implications for ecological functions and rural livelihoods

Abstract

Rural communities in the Himalayan Kingdom of Bhutan are dependant on natural capital for their livelihoods. Climate change impacts on ecosystem could have serious consequences for these communities but little research has been done to explore these potential impacts. In this study, we used Boosted Regression Tree (BRT) models to model current and potential future distribution of major timber species (Abies densa, Pinus wallichiana, Tsuga dumosa), fuelwood species (Quercus spp, Betula spp, Betula utilis, Rhododendron spp, Rhododendron arboreum) and an important non-timber resource (Ophiocordyceps sinensis) in Bhutan Himalayan region. Models were based on species presence and absence data from 575 plots and a new high-resolution climate dataset developed for Bhutan. Future projections were based on IPCC's representative concentration pathway (RCP 8.5) for the 2080s in Bhutan. Mean annual temperature and precipitation of driest quarters were found to be the most influential variables in modelling the current distribution of these species, with the distribution of most of the species projected to decrease significantly and shift to higher elevations. The current distribution of Ophiocordyceps sinensis was modelled to decrease by 79% at the national level with only 21% range overlap between current and future distributions. Current distribution of timber species like Abies densa and Tsuga dumosa were modelled to decline by 98% and 99% respectively at national level with very low range overlaps between current and future distribution suggesting high species vulnerability to climate change. In contrast, fuel wood species like Betula spp, Quercus spp, Rhododendron arboreum all exhibited less vulnerability to climate change with over 50% of their current range overlapping with future distribution across Bhutan and in the Nikachu watershed. These potential changes in distribution patterns of these species could impact on the functions and ecosystem services provided by these species and socio-economic conditions of rural communities reliant on these species for their livelihoods in Bhutan. Lower rates of global greenhouse gas emissions and adoption of adaptation measures and management interventions can reduce these potential impacts.