Modelling of past, current and future distribution of suitable habitat for Menelik's bushbuck (Tragelaphus sylvaticus meneliki Neumann, 1902) in the Ethiopian highlands.

Abstract

Background: Wildlife species adapted to the Afro-alpine highlands are vulnerable to loss of habitat due to global warming accompanying potential upward shifts and elevational range contractions of their preferred habitats. Understanding the trends in the shift of suitable habitats of endemic taxa is key to planning the conservation and management of species. Therefore, this study aimed to model the distribution of Menelik's bushbuck, a spiral-horned antelope endemic to Ethiopian highlands across the past (Last Glacial Maximum, and Mid-Holocene), present, and future.

Methods: We performed the ensemble modelling implemented in the "sdm" R package using 6 modelling techniques (MaxEnt, Generalized Linear Model, Generalized Additive Model, Random Forest, Boosted Regression Tree, and Multivariate Adaptive Regression Splines). We combined 248 occurrence points of Menelik's bushbuck with 12 climatic, topographic, and anthropogenic variables. We selected these variables from originally 24 variables using the VIF step procedure to avoid highly correlated predictor variables for the final model run.

Results: The performance of the ensemble model was excellent having AUC = 0.97 and TSS = 0.88 values. Bio6 (minimum temperature of the coldest month) contributed most to the distribution of Menelik's bushbuck followed by bio12 (annual precipitation) and elevation. The model projection estimated the suitable habitat of Menelik's bushbuck steadily decreases with increasing representative concentration pathways (RCP) scenarios and projection years. The current suitable habitat of this species is estimated to be 25,546 km² whereas the Mid-Holocene and the Last Glacial Maximum potential habitats was about 60,282.24 km² and 33,652 km² respectively. The magnitude of the loss of suitable habitats of Menelik's bushbuck will be highest in 2050 and 2070 under RCP 8.5 climate scenarios showing the loss in the currently suitable habitats of this species is over 95.1% and 99.8% respectively.

Conclusion: Melelik's bushbuck has lost suitable habitat since the LGM and the loss will be greatest in the future due to climate change and land use change. The sharp decline of the suitable habitat will greatly threaten the future survival of the species. Our modelling can assist in identifying potential refuge areas for the species to assist in its preservation.