Bioclimatic suitability models for current and future distribution of Elongated Tortoise (Indotestudo elongata) in Nepal

Abstract

The Elongated Tortoise (Indotestudo elongata) is the least known and most threatened species among all the vertebrates in the world. Observation for the previous climatic variation, future prediction on changes, and an exercise to explore the relation of climate change and its distribution has done in this study. The site of occurrence of the species is based on climatic suitability. The study basically focuses on whole lowland Nepal. The present distribution of this species and their further response to future climatic changes was done through Species Distribution Modelling (SDM). Seven environmental variables were analysed against the distribution of elongated tortoise under different climatic conditions; Shared Socio-economic Pathways (SSPs) 245 and 585 for the year 2050 and 2070 with the use of maximum entropy modeling (MaxEnt). A predicted distribution frame maps and estimated area using Arc GIS 10.8 was done for the study. Among seven bioclimatic variables, three variables were considered important factors where average temperature of wettest quarter (Bio8) contributed the highest (77.1%) followed by 8.6% for Bio5 (temperature of warmest month) and 7.4% for Bio12 (annual precipitation). When MaxEnt was used, the average area under the curve high (AUC) for I. elongata was 0.926, indicating the accuracy of the climatic suitability modeling. The suitability estimated by Maxent for elongated tortoise was 47,893 km 2 (24.42%) where, highly suitable area was approximately 27,822km 2 (14.19%) and moderately suitable area 20,071 km 2 (10.23%) for current scenario. The study also predicted that suitability will increase along with time as the proportion of moderately suitable areas would decline by 2070 under high emission scenarios SSPs585(2070).