Understanding the impact of climate change on the habitat of the rufous-necked hornbill (Aceros nipalensis) (Hodgson, 1829) using MaxEnt modeling in Bhutan

Climate change and anthropogenic activities such as deforestation, forest fires, and land use change are serious threats to faunal and avian species including their habitat and population. Using maximum entropy (MaxEnt) modeling, this study assessed the current and future suitable habitats of the rufous-necked hornbill (Aceros nipalensis) under SSP1-2.6 and SSP3-7 climate scenarios for 2021–2040 and 2061–2080 in Bhutan. The impact of climate change on species’s habitat was evaluated using 158 occurrence points collected as presence-only data and the environmental covariates obtained from www.worldclim.org. ENM-evaluate was conducted in R to obtain MaxEnt settings and bias files. A total of 10,000 background points with a regularization multiplier of 1 and linear and quadratic features were selected to build a model in MaxEnt software. A large area of Bhutan is predicted as an unsuitable habitat, accounting for 70.61% (27,100 km2), and only 29.39% (11,284.7 km2) is predicted as a suitable habitat area, with 9197.19 km2 outside of the protected area. The annual mean temperature has a significant influence (54.1%) on the model, followed by elevation (13.1%) and the least by slope (1.5%). The suitable area is expected to decline from 3.3% (1278.32 km2) under SSP1-2.6 to 1.42% (549.54 km2) under SSP3-7 in 2021–2040 and 2061–2080, respectively. The study also found that the present suitable habitat will shift towards the southeast in the future. The results of the study call for the relevant agencies to implement projects in suitable areas to protect the habitats of the rufous-necked hornbill and conserve the species. The inclusion of variables such as distance from the settlement, road, and river is recommended for future studies.