Vanishing Refuges: Unraveling the Climate Change Impact on the Critically Endangered Black Softshell Turtle Nilssonia nigricans in Northeastern India

Abstract

Abstract Reptilian species can be regarded as a bioindicator of climate change. However, limited studies are available on the effect of climate change on the distribution of reptiles in India. Nilssonia nigricans is a Critically Endangered Soft-shell Turtle found in Northeastern India, facing severe threats due to the Anthropocene. Previously, this species was considered extinct in the wild; however, recently, some populations have been discovered in the Brahmaputra Valley. In this context, a study was initiated to understand the impact of climate change on the distribution of N. nigricans. Maximum Entropy (MaxEnt) is employed to predict the potential distribution range of this species for two time periods: the 2050s (2041–2060) and the 2070s (2061–2080) under both RCP 4.5 and RCP 8.5 scenarios. The study found that the Mean Temperature of the Wettest Quarter, Elevation and Precipitation Seasonality will be the major factors that determine the distribution of N. nigricans. The model indicated that under current conditions, 21.78% of the study area provides a suitable habitat for N. nigricans. Future predictions suggest a potential range contraction of 16.09% during the 2050s under RCP 4.5 and an increase of 25.83% in the 2050s under the RCP 8.5 scenario. However, in the 2070s, the habitat range of this species may decline to 10.77% under RCP 4.5 and 19.97% under RCP 8.5. The comparison of various RCP scenarios illustrated that the habitat range is shrinking under RCP 4.5 scenarios. Among the states, Assam is the only place that shows the highest potential for suitable sites, covering an area of 58,535 km2 (58.47%), while the remaining 41,581 km2 (41.53%) is deemed unsuitable for its current distribution. The study reveals that N. nigricans serves as a bioindicator of climate change in Northeast India, and the study's results will be helpful in creating conservation and management attention for the species.